From 39806d8b1611d48ff725ab7c02bfcf1524b33fac Mon Sep 17 00:00:00 2001
From: Thomas Flayols <thomas.flayols@gmail.com>
Date: Wed, 27 Aug 2025 18:28:08 +0200
Subject: [PATCH 01/11] Add a PIO program for ADC bu79100g, work in progress

---
 src/current/rp2350/README.md                 | 12 +++++
 src/current/rp2350/RP2350PIOCurrentSense.cpp | 50 ++++++++++++++++--
 src/current/rp2350/RP2350PIOCurrentSense.h   | 13 ++++-
 src/current/rp2350/bu79100g_parallel3.pio    | 30 +++++++++++
 src/current/rp2350/bu79100g_parallel3.pio.h  | 55 ++++++++++++++++++++
 5 files changed, 153 insertions(+), 7 deletions(-)
 create mode 100644 src/current/rp2350/bu79100g_parallel3.pio
 create mode 100644 src/current/rp2350/bu79100g_parallel3.pio.h

diff --git a/src/current/rp2350/README.md b/src/current/rp2350/README.md
index 0f37358..30937b9 100644
--- a/src/current/rp2350/README.md
+++ b/src/current/rp2350/README.md
@@ -6,4 +6,16 @@
 Implementation of current sensing on RP2350 using the PIO to read SPI based ADCs.
 
 
+Temporarly, for this to work, we need to add a PWM chanell in Arduino-FOC rp2040 hardware specific files. The duty cyctle needs to be computed to trigger the ADC at the right-time.
+The PWM pin is hardcoded to GPIO11 for now.
 
+
+
+## Compilling the PIO program
+To manually compile the PIO files (generating a .pio.h from a pio), you need to instal pioasm.
+Note for self, on my setup:
+
+```
+export PIOASM="$HOME/.arduino15/packages/rp2040/tools/pqt-pioasm/4.1.0-1aec55e/pioasm"
+"$PIOASM" -v 1 bu79100g_parallel3.pio bu79100g_parallel3.pio.h
+```
\ No newline at end of file
diff --git a/src/current/rp2350/RP2350PIOCurrentSense.cpp b/src/current/rp2350/RP2350PIOCurrentSense.cpp
index cddc569..836e45d 100644
--- a/src/current/rp2350/RP2350PIOCurrentSense.cpp
+++ b/src/current/rp2350/RP2350PIOCurrentSense.cpp
@@ -1,13 +1,16 @@
     #include "RP2350PIOCurrentSense.h"
 
-    RP2350PIOCurrentSense::RP2350PIOCurrentSense(float gain, uint32_t max_adc_value, int pinA, int pinB, int pinC) : CurrentSense() {
-        this->pinA = pinA;
-        this->pinB = pinB;
-        this->pinC = pinC;
+    RP2350PIOCurrentSense::RP2350PIOCurrentSense(float gain, uint32_t max_adc_value, int pinSCK, int pinCSB, int pinD0) : CurrentSense() {
+        this->pinSCK = pinSCK;
+        this->pinCSB = pinCSB;
+        this->pinD0 = pinD0;
+        this->pinD1 = pinD0+1;
+        this->pinD2 = pinD0+2;
         this->gain_a = gain;
         this->gain_b = gain;
         this->gain_c = gain;
         this->max_adc_value = max_adc_value;
+
     };
 
 
@@ -19,13 +22,50 @@
         // TODO check that pins are valid for PIO use (e.g. consecutive pins on same bank)
         // TODO check that driver is linked
         
-        // TODO init PIO        
+        // Done init PIO        
         // TODO init ADC via SPI
         // TODO init DMA to transfer ADC data to memory buffer
         // TODO init timer to trigger PIO conversions at required frequency (check driver settings)
         //      TDB: do we need config input to know which timer slice and channel to use? or can we pick automatically?
         // TODO start everything up
 
+        
+        float sck_hz = 20e6;
+        PIO pio = pio0; 
+        int sm = pio_claim_unused_sm(pio0, false);
+        if (sm < 0) { pio = pio1; sm = pio_claim_unused_sm(pio1, true); }
+
+        uint off = pio_add_program(pio, &bu79100g_parallel3_program);
+        pio_sm_config c = bu79100g_parallel3_program_get_default_config(off);
+
+        // Map pins to the SM
+        sm_config_set_in_pins(&c, this->pinD0);                // reads D0..D2
+        sm_config_set_set_pins(&c, this->pinCSB, 1);           // CSB (1 pin)
+        sm_config_set_sideset_pins(&c, this->pinSCK);          // SCK (sideset)
+
+        // Put pins into PIO control
+        pio_gpio_init(pio, this->pinSCK);
+        pio_gpio_init(pio, this->pinCSB);
+        pio_gpio_init(pio, this->pinD0);
+        pio_gpio_init(pio, this->pinD1);
+        pio_gpio_init(pio, this->pinD2);
+
+        // Directions (from the SM’s point of view)
+        pio_sm_set_consecutive_pindirs(pio, sm, this->pinSCK, 1, true);   // SCK out
+        pio_sm_set_consecutive_pindirs(pio, sm, this->pinCSB, 1, true);   // CS out
+        pio_sm_set_consecutive_pindirs(pio, sm, this->pinD0,  3, false);  // D0..D2 in
+
+        // Shift config: right, autopush every 24 bits (two pushes per conversion)
+        sm_config_set_in_shift(&c, true, true, 24);
+
+        // SCK ≈ clk_sys / (2 * clkdiv) because each SCK period = 2 instructions
+        float div = (float)clock_get_hz(clk_sys) / (2.0f * sck_hz);
+        sm_config_set_clkdiv(&c, div);
+
+        // Init & start the SM
+        pio_sm_init(pio, sm, off, &c);
+        pio_sm_set_enabled(pio, sm, true);
+
         return 0;
     };
 
diff --git a/src/current/rp2350/RP2350PIOCurrentSense.h b/src/current/rp2350/RP2350PIOCurrentSense.h
index 3bcadd8..5d5371a 100644
--- a/src/current/rp2350/RP2350PIOCurrentSense.h
+++ b/src/current/rp2350/RP2350PIOCurrentSense.h
@@ -2,11 +2,11 @@
 #pragma once
 
 #include "common/base_classes/CurrentSense.h"
-
+#include "bu79100g_parallel3.pio.h"
 
 class RP2350PIOCurrentSense: public CurrentSense {
   public:
-    RP2350PIOCurrentSense(float gain, uint32_t max_adc_value, int pinA, int pinB, int pinC = _NC);
+    RP2350PIOCurrentSense(float gain, uint32_t max_adc_value, int pinSCK, int pinCSB, int pinD0);
     ~RP2350PIOCurrentSense();
 
     int init() override;
@@ -14,4 +14,13 @@ class RP2350PIOCurrentSense: public CurrentSense {
     PhaseCurrent_s getPhaseCurrents() override;
   protected:
     uint32_t max_adc_value; //!< maximum ADC value (e.g. 4096 for 12 bit ADC)
+    int pinCSB;
+    int pinSCK;
+    int pinD0;
+    int pinD1;
+    int pinD2;
+    int gain_a;
+    int gain_b;
+    int gain_c;
+
 };
diff --git a/src/current/rp2350/bu79100g_parallel3.pio b/src/current/rp2350/bu79100g_parallel3.pio
new file mode 100644
index 0000000..e242011
--- /dev/null
+++ b/src/current/rp2350/bu79100g_parallel3.pio
@@ -0,0 +1,30 @@
+.program bu79100g_parallel3
+; BU79100G-LA parallel read of 3 ADCs with a trigger GPIO
+; sideset pin: SCK (1 pin), CPOL=1 idle HIGH
+; set pin:     CSB (1 pin)
+; in_base:     D0..D2 (3 contiguous input pins)
+
+.side_set 1 opt            ; 1 sideset bit to drive SCK
+
+.wrap_target
+    set pins, 1   side 1   ; CSB=1, SCK=1
+    ; -------- wait external falling edge on absolute GPIO ----------
+    wait 1 gpio 11 ; TODO, we will need to have this pin setable from the C code. direcetly edit the program?
+    wait 0 gpio 11
+    set pins, 0   side 1          ; CS=0, SCK=1
+    set x, 15     side 1          ; prepare loop cpt
+    ; -------- 16 dummy clocks (no sampling) ----------------------- 
+dummy_loop:
+        nop           side 0          ; SCK=0
+        jmp x--, dummy_loop side 1    ; SCK=1
+    set pins, 1   side 1       ; CSB=0, keep SCK=HIGH at CSB falling (datasheet rec.)
+    set x, 15     side 1
+    set pins, 0
+    ; -------- 16 real clocks, sample on SCK rising edge -----------
+read_loop:    
+        nop           side 1  ;DEBUG so we don't have to wait for autopush.
+        ;in  pins, 3   side 1          ; SCK=1, sample D2..D0 on rising edge
+        jmp x--, read_loop side 0      ; SCK=0
+    ; -------- finish conversion -----------------------------------
+    set pins, 1   side 1               ; CSB=1, SCK=1
+.wrap
\ No newline at end of file
diff --git a/src/current/rp2350/bu79100g_parallel3.pio.h b/src/current/rp2350/bu79100g_parallel3.pio.h
new file mode 100644
index 0000000..a8e3401
--- /dev/null
+++ b/src/current/rp2350/bu79100g_parallel3.pio.h
@@ -0,0 +1,55 @@
+// -------------------------------------------------- //
+// This file is autogenerated by pioasm; do not edit! //
+// -------------------------------------------------- //
+
+#pragma once
+
+#if !PICO_NO_HARDWARE
+#include "hardware/pio.h"
+#endif
+
+// ------------------ //
+// bu79100g_parallel3 //
+// ------------------ //
+
+#define bu79100g_parallel3_wrap_target 0
+#define bu79100g_parallel3_wrap 12
+#define bu79100g_parallel3_pio_version 1
+
+static const uint16_t bu79100g_parallel3_program_instructions[] = {
+            //     .wrap_target
+    0xf801, //  0: set    pins, 1         side 1
+    0x208b, //  1: wait   1 gpio, 11
+    0x200b, //  2: wait   0 gpio, 11
+    0xf800, //  3: set    pins, 0         side 1
+    0xf82f, //  4: set    x, 15           side 1
+    0xb042, //  5: nop                    side 0
+    0x1845, //  6: jmp    x--, 5          side 1
+    0xf801, //  7: set    pins, 1         side 1
+    0xf82f, //  8: set    x, 15           side 1
+    0xe000, //  9: set    pins, 0
+    0xb842, // 10: nop                    side 1
+    0x104a, // 11: jmp    x--, 10         side 0
+    0xf801, // 12: set    pins, 1         side 1
+            //     .wrap
+};
+
+#if !PICO_NO_HARDWARE
+static const struct pio_program bu79100g_parallel3_program = {
+    .instructions = bu79100g_parallel3_program_instructions,
+    .length = 13,
+    .origin = -1,
+    .pio_version = bu79100g_parallel3_pio_version,
+#if PICO_PIO_VERSION > 0
+    .used_gpio_ranges = 0x1
+#endif
+};
+
+static inline pio_sm_config bu79100g_parallel3_program_get_default_config(uint offset) {
+    pio_sm_config c = pio_get_default_sm_config();
+    sm_config_set_wrap(&c, offset + bu79100g_parallel3_wrap_target, offset + bu79100g_parallel3_wrap);
+    sm_config_set_sideset(&c, 2, true, false);
+    return c;
+}
+#endif
+

From 9268cf372ad60d48b157d7a92caa8d29fff67b2b Mon Sep 17 00:00:00 2001
From: Thomas Flayols <thomas.flayols@gmail.com>
Date: Wed, 27 Aug 2025 19:20:04 +0200
Subject: [PATCH 02/11] add the option to select any trigger pin.

---
 src/current/rp2350/RP2350PIOCurrentSense.cpp | 14 ++++++++++++--
 src/current/rp2350/RP2350PIOCurrentSense.h   |  3 ++-
 src/current/rp2350/bu79100g_parallel3.pio    |  4 ++--
 3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/src/current/rp2350/RP2350PIOCurrentSense.cpp b/src/current/rp2350/RP2350PIOCurrentSense.cpp
index 836e45d..fcee9c6 100644
--- a/src/current/rp2350/RP2350PIOCurrentSense.cpp
+++ b/src/current/rp2350/RP2350PIOCurrentSense.cpp
@@ -1,11 +1,12 @@
     #include "RP2350PIOCurrentSense.h"
 
-    RP2350PIOCurrentSense::RP2350PIOCurrentSense(float gain, uint32_t max_adc_value, int pinSCK, int pinCSB, int pinD0) : CurrentSense() {
+    RP2350PIOCurrentSense::RP2350PIOCurrentSense(float gain, uint32_t max_adc_value, int pinSCK, int pinCSB, int pinD0, int pinTRIG) : CurrentSense() {
         this->pinSCK = pinSCK;
         this->pinCSB = pinCSB;
         this->pinD0 = pinD0;
         this->pinD1 = pinD0+1;
         this->pinD2 = pinD0+2;
+        this->pinTRIG = pinTRIG;
         this->gain_a = gain;
         this->gain_b = gain;
         this->gain_c = gain;
@@ -35,7 +36,16 @@
         int sm = pio_claim_unused_sm(pio0, false);
         if (sm < 0) { pio = pio1; sm = pio_claim_unused_sm(pio1, true); }
 
-        uint off = pio_add_program(pio, &bu79100g_parallel3_program);
+        // --- patch program instructions with chosen trigger pin ---
+        size_t prog_len = bu79100g_parallel3_program.length;
+        uint16_t insns[prog_len];
+        memcpy(insns, bu79100g_parallel3_program_instructions, sizeof(insns));
+        insns[1] = (insns[1] & ~0x1Fu) | (this->pinTRIG & 0x1Fu);
+        insns[2] = (insns[2] & ~0x1Fu) | (this->pinTRIG & 0x1Fu);
+        struct pio_program prog = bu79100g_parallel3_program; // copy metadata
+        prog.instructions = insns;
+    
+        uint off = pio_add_program(pio, &prog);
         pio_sm_config c = bu79100g_parallel3_program_get_default_config(off);
 
         // Map pins to the SM
diff --git a/src/current/rp2350/RP2350PIOCurrentSense.h b/src/current/rp2350/RP2350PIOCurrentSense.h
index 5d5371a..e74d1a4 100644
--- a/src/current/rp2350/RP2350PIOCurrentSense.h
+++ b/src/current/rp2350/RP2350PIOCurrentSense.h
@@ -6,7 +6,7 @@
 
 class RP2350PIOCurrentSense: public CurrentSense {
   public:
-    RP2350PIOCurrentSense(float gain, uint32_t max_adc_value, int pinSCK, int pinCSB, int pinD0);
+    RP2350PIOCurrentSense(float gain, uint32_t max_adc_value, int pinSCK, int pinCSB, int pinD0, int pinTRIG);
     ~RP2350PIOCurrentSense();
 
     int init() override;
@@ -19,6 +19,7 @@ class RP2350PIOCurrentSense: public CurrentSense {
     int pinD0;
     int pinD1;
     int pinD2;
+    int pinTRIG;
     int gain_a;
     int gain_b;
     int gain_c;
diff --git a/src/current/rp2350/bu79100g_parallel3.pio b/src/current/rp2350/bu79100g_parallel3.pio
index e242011..279ea71 100644
--- a/src/current/rp2350/bu79100g_parallel3.pio
+++ b/src/current/rp2350/bu79100g_parallel3.pio
@@ -9,8 +9,8 @@
 .wrap_target
     set pins, 1   side 1   ; CSB=1, SCK=1
     ; -------- wait external falling edge on absolute GPIO ----------
-    wait 1 gpio 11 ; TODO, we will need to have this pin setable from the C code. direcetly edit the program?
-    wait 0 gpio 11
+    wait 1 gpio 11 ;THIS INSTRUCTION WILL BE PATCHED AT RUNTIME TO CHANGE GPIO. DO NOT MOVE IT WITHOUT CHANGING PIO INIT.
+    wait 0 gpio 11 ;THIS INSTRUCTION WILL BE PATCHED AT RUNTIME TO CHANGE GPIO. DO NOT MOVE IT WITHOUT CHANGING PIO INIT.
     set pins, 0   side 1          ; CS=0, SCK=1
     set x, 15     side 1          ; prepare loop cpt
     ; -------- 16 dummy clocks (no sampling) ----------------------- 

From 3f815f839867c1c35c395e26981a3c8394f7ed05 Mon Sep 17 00:00:00 2001
From: Thomas Flayols <thomas.flayols@gmail.com>
Date: Wed, 27 Aug 2025 19:32:32 +0200
Subject: [PATCH 03/11] add a bit more info and dev status in readme.

---
 src/current/rp2350/README.md | 53 +++++++++++++++++++++++++++++++++++-
 1 file changed, 52 insertions(+), 1 deletion(-)

diff --git a/src/current/rp2350/README.md b/src/current/rp2350/README.md
index 30937b9..42e550f 100644
--- a/src/current/rp2350/README.md
+++ b/src/current/rp2350/README.md
@@ -4,12 +4,63 @@
 *warning* Work in progress
 
 Implementation of current sensing on RP2350 using the PIO to read SPI based ADCs.
+Wiring:
 
+* SCK_PIN -> Clock pin shared with 3 ADCs
+* CSB_PIN -> Chip Select pin shared with 3 ADCs
+* D0, D1 D2 -> The 3 data output from the ADCs. Needs to be contigus (D1=D0+1 D2=D1+1)
 
 Temporarly, for this to work, we need to add a PWM chanell in Arduino-FOC rp2040 hardware specific files. The duty cyctle needs to be computed to trigger the ADC at the right-time.
-The PWM pin is hardcoded to GPIO11 for now.
 
 
+TODO:
+* Init a the DMA or IRQ to read samples from PIO.
+* Activate the push of adc data in PIO program (disabled for tests)
+* Find a way to setup the trigger PWM from the driver, or change the arduino-foc lib.
+
+
+
+# Example:
+```
+// Open loop motor control example With current readings (work in progress)
+#include <SimpleFOC.h>
+#include "pico/stdlib.h"
+#include "hardware/pio.h"
+#include "hardware/clocks.h"
+#include <SimpleFOCDrivers.h>
+#include "current/rp2350/RP2350PIOCurrentSense.h"
+
+static const uint SCK_PIN   = 2;  // sideset pin
+static const uint CSB_PIN   = 3;  // set pin
+static const uint D0_PIN    = 4;  // D0..D2 must be contiguous (D1=D0+1, D2=D0+2)
+static const uint TRIG_PIN  = 8;  // This need to be also configure as an extra PWM output with custom fixed duty cycle. For now let's just one of the phase as the trigger.
+
+BLDCMotor motor = BLDCMotor(11);
+BLDCDriver3PWM driver = BLDCDriver3PWM(7, 8, 9);
+RP2350PIOCurrentSense curr = RP2350PIOCurrentSense(1.0, 4096,SCK_PIN, CSB_PIN, D0_PIN, TRIG_PIN);
+
+float target_velocity = 0.2;
+
+void setup() {
+  Serial.begin(115200);
+  SimpleFOCDebug::enable(&Serial);
+  driver.voltage_power_supply = 12;
+  driver.voltage_limit = 12;
+  driver.init();
+  motor.linkDriver(&driver);
+  motor.voltage_limit = 2;   // [V]
+  motor.controller = MotionControlType::velocity_openloop;
+  motor.init();
+  Serial.println("Motor ready!");
+  _delay(100);
+  curr.init();
+}
+
+void loop() {
+  motor.move(target_velocity);
+}
+```
+
 
 ## Compilling the PIO program
 To manually compile the PIO files (generating a .pio.h from a pio), you need to instal pioasm.

From cc97db0503c7871d38fce109dad04508a6d97c57 Mon Sep 17 00:00:00 2001
From: Thomas Flayols <thomas.flayols@gmail.com>
Date: Tue, 2 Sep 2025 18:19:20 +0200
Subject: [PATCH 04/11] first working version of a PIO to DMA setup without CPU
 calls. Transmitting 64bits per samples, in a ring buffer from witch the CPU
 can take the last samples.

---
 src/current/rp2350/RP2350PIOCurrentSense.cpp | 55 ++++++++++++++++----
 src/current/rp2350/RP2350PIOCurrentSense.h   | 20 ++++++-
 src/current/rp2350/bu79100g_parallel3.pio    | 11 ++--
 src/current/rp2350/bu79100g_parallel3.pio.h  |  8 +--
 4 files changed, 77 insertions(+), 17 deletions(-)

diff --git a/src/current/rp2350/RP2350PIOCurrentSense.cpp b/src/current/rp2350/RP2350PIOCurrentSense.cpp
index fcee9c6..c6208f4 100644
--- a/src/current/rp2350/RP2350PIOCurrentSense.cpp
+++ b/src/current/rp2350/RP2350PIOCurrentSense.cpp
@@ -11,7 +11,6 @@
         this->gain_b = gain;
         this->gain_c = gain;
         this->max_adc_value = max_adc_value;
-
     };
 
 
@@ -24,17 +23,16 @@
         // TODO check that driver is linked
         
         // Done init PIO        
-        // TODO init ADC via SPI
-        // TODO init DMA to transfer ADC data to memory buffer
+        // TODO init ADC via SPI (Only for ADC with MOSI input)
+        // Done init DMA to transfer ADC data to memory buffer
         // TODO init timer to trigger PIO conversions at required frequency (check driver settings)
         //      TDB: do we need config input to know which timer slice and channel to use? or can we pick automatically?
         // TODO start everything up
 
-        
         float sck_hz = 20e6;
         PIO pio = pio0; 
-        int sm = pio_claim_unused_sm(pio0, false);
-        if (sm < 0) { pio = pio1; sm = pio_claim_unused_sm(pio1, true); }
+        int sm = pio_claim_unused_sm(pio0, true);
+        //if (sm < 0) { pio = pio1; sm = pio_claim_unused_sm(pio1, true); } //For now, let say we have to use PIO0, this is simpler for quick DMA setup
 
         // --- patch program instructions with chosen trigger pin ---
         size_t prog_len = bu79100g_parallel3_program.length;
@@ -65,17 +63,56 @@
         pio_sm_set_consecutive_pindirs(pio, sm, this->pinCSB, 1, true);   // CS out
         pio_sm_set_consecutive_pindirs(pio, sm, this->pinD0,  3, false);  // D0..D2 in
 
-        // Shift config: right, autopush every 24 bits (two pushes per conversion)
-        sm_config_set_in_shift(&c, true, true, 24);
+        // Shift config: right, autopush every 32 bits (two pushes per conversion)
+        sm_config_set_in_shift(&c, true, true, 32);
 
         // SCK ≈ clk_sys / (2 * clkdiv) because each SCK period = 2 instructions
         float div = (float)clock_get_hz(clk_sys) / (2.0f * sck_hz);
         sm_config_set_clkdiv(&c, div);
 
-        // Init & start the SM
+        // Init the SM
         pio_sm_init(pio, sm, off, &c);
+
+       //DMA Setup
+       //dma_a is set to read from PIO RX FIFO and write to 'buff' buffer memory
+        dma_a = dma_claim_unused_channel(true);
+        dma_b = dma_claim_unused_channel(true);
+        // ---------------------- DMA A: PIO RX FIFO -> buff[] with WRITE ring ----------------------
+        dma_channel_config ca = dma_channel_get_default_config(dma_a);
+        channel_config_set_read_increment(&ca, false);
+        channel_config_set_write_increment(&ca, true);
+        channel_config_set_transfer_data_size(&ca, DMA_SIZE_32);
+        channel_config_set_dreq(&ca, DREQ_PIO0_RX0 + sm);
+        channel_config_set_chain_to(&ca, dma_b);  // A -> B when count hits 0
+
+        // Enable WRITE-side ring over the whole buffer span (power-of-two bytes)
+        // size_bits = log2(RING_BYTES)
+        channel_config_set_ring(&ca, /*write=*/true, /*size_bits=*/__builtin_ctz(RING_BYTES));
+
+        dma_channel_set_config(dma_a, &ca, false);
+        dma_channel_set_read_addr(dma_a, &pio->rxf[sm], false);
+        dma_channel_set_write_addr(dma_a, (void*)buff, false);
+        dma_channel_set_trans_count(dma_a, RING_WORDS, false);
+
+        // ---------------------- DMA B: rearm A with ONE 32-bit write ----------------------
+        dma_channel_config cb = dma_channel_get_default_config(dma_b);
+        channel_config_set_read_increment(&cb, false);
+        channel_config_set_write_increment(&cb, false);
+        channel_config_set_transfer_data_size(&cb, DMA_SIZE_32);
+
+        // Write 1 word to A.AL1_TRANSFER_COUNT_TRIG (this sets count and re-starts A)
+        dma_channel_configure(
+            dma_b, &cb,
+            (void*)&dma_hw->ch[dma_a].al1_transfer_count_trig,
+            (const void*)&reload_count,
+            1, false
+        );
+
+        // Go!
+        dma_channel_start(dma_a);
         pio_sm_set_enabled(pio, sm, true);
 
+
         return 0;
     };
 
diff --git a/src/current/rp2350/RP2350PIOCurrentSense.h b/src/current/rp2350/RP2350PIOCurrentSense.h
index e74d1a4..585a3cb 100644
--- a/src/current/rp2350/RP2350PIOCurrentSense.h
+++ b/src/current/rp2350/RP2350PIOCurrentSense.h
@@ -3,6 +3,8 @@
 
 #include "common/base_classes/CurrentSense.h"
 #include "bu79100g_parallel3.pio.h"
+#include "hardware/dma.h"
+#include "hardware/sync.h"
 
 class RP2350PIOCurrentSense: public CurrentSense {
   public:
@@ -12,7 +14,21 @@ class RP2350PIOCurrentSense: public CurrentSense {
     int init() override;
 
     PhaseCurrent_s getPhaseCurrents() override;
-  protected:
+  
+    static constexpr uint32_t RING_WORDS    = 16;   // ring span (needs to be a power of two)
+    static constexpr uint32_t RING_BYTES = RING_WORDS * 4;
+
+    // Buffer base must be aligned to ring span for write-ring:
+    alignas(RING_BYTES) volatile uint32_t buff[RING_WORDS];
+
+    // Single word used by DMA B to rearm A:
+    alignas(4) volatile uint32_t reload_count = RING_WORDS;
+
+
+    int dma_a = -1; // PIO RX -> ring (streamer)
+    int dma_b = -1; // reloader 
+
+
     uint32_t max_adc_value; //!< maximum ADC value (e.g. 4096 for 12 bit ADC)
     int pinCSB;
     int pinSCK;
@@ -23,5 +39,5 @@ class RP2350PIOCurrentSense: public CurrentSense {
     int gain_a;
     int gain_b;
     int gain_c;
-
+  protected: //For debug, all public
 };
diff --git a/src/current/rp2350/bu79100g_parallel3.pio b/src/current/rp2350/bu79100g_parallel3.pio
index 279ea71..cb3c52c 100644
--- a/src/current/rp2350/bu79100g_parallel3.pio
+++ b/src/current/rp2350/bu79100g_parallel3.pio
@@ -5,7 +5,6 @@
 ; in_base:     D0..D2 (3 contiguous input pins)
 
 .side_set 1 opt            ; 1 sideset bit to drive SCK
-
 .wrap_target
     set pins, 1   side 1   ; CSB=1, SCK=1
     ; -------- wait external falling edge on absolute GPIO ----------
@@ -22,9 +21,15 @@ dummy_loop:
     set pins, 0
     ; -------- 16 real clocks, sample on SCK rising edge -----------
 read_loop:    
-        nop           side 1  ;DEBUG so we don't have to wait for autopush.
-        ;in  pins, 3   side 1          ; SCK=1, sample D2..D0 on rising edge
+        ;nop          side 1  ;DEBUG so we don't have to wait for autopush.
+        in  pins, 4   side 1          ; SCK=1, sample D2..D0 on rising edge  ;Note, Here I had to read 4 pins instead of 3. It seems that with 3, a bit is lost after the first push. Need to read the doc again
         jmp x--, read_loop side 0      ; SCK=0
     ; -------- finish conversion -----------------------------------
     set pins, 1   side 1               ; CSB=1, SCK=1
+    ; -------- Pad with 0 ------------------------------------------
+    ;set x, 0        ; Clear x
+    ;mov x, ~x 
+    ;in x, 16        ; Push 16 bits of 1 into ISR
+
+    ;push 
 .wrap
\ No newline at end of file
diff --git a/src/current/rp2350/bu79100g_parallel3.pio.h b/src/current/rp2350/bu79100g_parallel3.pio.h
index a8e3401..63f06d5 100644
--- a/src/current/rp2350/bu79100g_parallel3.pio.h
+++ b/src/current/rp2350/bu79100g_parallel3.pio.h
@@ -13,7 +13,7 @@
 // ------------------ //
 
 #define bu79100g_parallel3_wrap_target 0
-#define bu79100g_parallel3_wrap 12
+#define bu79100g_parallel3_wrap 14
 #define bu79100g_parallel3_pio_version 1
 
 static const uint16_t bu79100g_parallel3_program_instructions[] = {
@@ -28,16 +28,18 @@ static const uint16_t bu79100g_parallel3_program_instructions[] = {
     0xf801, //  7: set    pins, 1         side 1
     0xf82f, //  8: set    x, 15           side 1
     0xe000, //  9: set    pins, 0
-    0xb842, // 10: nop                    side 1
+    0x5804, // 10: in     pins, 4         side 1
     0x104a, // 11: jmp    x--, 10         side 0
     0xf801, // 12: set    pins, 1         side 1
+    0xe020, // 13: set    x, 0
+    0xa029, // 14: mov    x, ~x
             //     .wrap
 };
 
 #if !PICO_NO_HARDWARE
 static const struct pio_program bu79100g_parallel3_program = {
     .instructions = bu79100g_parallel3_program_instructions,
-    .length = 13,
+    .length = 15,
     .origin = -1,
     .pio_version = bu79100g_parallel3_pio_version,
 #if PICO_PIO_VERSION > 0

From 5e54639f6cee8b5d4d3e6e81e116c92bcf819a72 Mon Sep 17 00:00:00 2001
From: Thomas Flayols <thomas.flayols@gmail.com>
Date: Wed, 3 Sep 2025 14:50:58 +0200
Subject: [PATCH 05/11] add code to read the current from last measurement in
 buffer.

---
 src/current/rp2350/RP2350PIOCurrentSense.cpp | 38 ++++++++++++++++++--
 src/current/rp2350/RP2350PIOCurrentSense.h   | 10 +++---
 2 files changed, 39 insertions(+), 9 deletions(-)

diff --git a/src/current/rp2350/RP2350PIOCurrentSense.cpp b/src/current/rp2350/RP2350PIOCurrentSense.cpp
index c6208f4..90aa516 100644
--- a/src/current/rp2350/RP2350PIOCurrentSense.cpp
+++ b/src/current/rp2350/RP2350PIOCurrentSense.cpp
@@ -112,14 +112,46 @@
         dma_channel_start(dma_a);
         pio_sm_set_enabled(pio, sm, true);
 
-
         return 0;
     };
 
+    void extract_bit_interleaved(const uint32_t w0, const uint32_t w1, uint32_t *a, uint32_t *b, uint32_t *c, uint32_t *d) {
+        *a = 0;
+        *b = 0;
+        *c = 0;
+        *d = 0;
+        for (int i = 0; i < 64; i += 4) {
+            uint32_t w = (i < 32) ? w1 : w0;
+            int shift = 28 - (i % 32);  // 28, 24, ..., 0 for each group of 4 bits
+
+            uint32_t group = (w >> shift) & 0xF;  // extract aN bN cN dN
+
+            *a = (*a << 1) | ((group >> 0) & 0x1);
+            *b = (*b << 1) | ((group >> 1) & 0x1);
+            *c = (*c << 1) | ((group >> 2) & 0x1);
+            *d = (*d << 1) | ((group >> 3) & 0x1);
+        }
+    }
+
     PhaseCurrent_s RP2350PIOCurrentSense::getPhaseCurrents() {
         PhaseCurrent_s current;
-        // TODO copy values from latest ADC reading
-        // TODO process raw values to get currents in mAmps
+
+        const uintptr_t base = (uintptr_t)buff;
+        //Get the index the DMA is about to write
+        const uint32_t i_dma = (dma_hw->ch[dma_a].write_addr - base)>>2;
+        //For a safe read, get the one that is an even number and at least <2.wi, manage looping
+        const uint32_t i_last = (i_dma <= 1) ? RING_WORDS -2 : ((i_dma / 2)*2 - 2);
+        //copy them quickly (before print!)
+        const uint32_t w0 = buff[i_last];
+        const uint32_t w1 = buff[i_last+1];
+        //Reconstruct the 3 current from interleaved data
+        uint32_t a,b,c,d = 0;
+        extract_bit_interleaved(w0,w1, &a, &b, &c, &d);    
+
+        current.a = (0x00000fff & a) * gain_a;
+        current.b = (0x00000fff & b) * gain_b;
+        current.c = (0x00000fff & c) * gain_c;
+        
         return current;
     };
 
diff --git a/src/current/rp2350/RP2350PIOCurrentSense.h b/src/current/rp2350/RP2350PIOCurrentSense.h
index 585a3cb..0100172 100644
--- a/src/current/rp2350/RP2350PIOCurrentSense.h
+++ b/src/current/rp2350/RP2350PIOCurrentSense.h
@@ -15,7 +15,7 @@ class RP2350PIOCurrentSense: public CurrentSense {
 
     PhaseCurrent_s getPhaseCurrents() override;
   
-    static constexpr uint32_t RING_WORDS    = 16;   // ring span (needs to be a power of two)
+    static constexpr uint32_t RING_WORDS    = 64;   // ring span (needs to be a power of two)
     static constexpr uint32_t RING_BYTES = RING_WORDS * 4;
 
     // Buffer base must be aligned to ring span for write-ring:
@@ -24,11 +24,9 @@ class RP2350PIOCurrentSense: public CurrentSense {
     // Single word used by DMA B to rearm A:
     alignas(4) volatile uint32_t reload_count = RING_WORDS;
 
-
     int dma_a = -1; // PIO RX -> ring (streamer)
     int dma_b = -1; // reloader 
 
-
     uint32_t max_adc_value; //!< maximum ADC value (e.g. 4096 for 12 bit ADC)
     int pinCSB;
     int pinSCK;
@@ -36,8 +34,8 @@ class RP2350PIOCurrentSense: public CurrentSense {
     int pinD1;
     int pinD2;
     int pinTRIG;
-    int gain_a;
-    int gain_b;
-    int gain_c;
+    float gain_a;
+    float gain_b;
+    float gain_c;
   protected: //For debug, all public
 };

From 4aa83b6eec5d7fa6aa828f98629ba83f8bab6570 Mon Sep 17 00:00:00 2001
From: Thomas Flayols <thomas.flayols@gmail.com>
Date: Wed, 3 Sep 2025 15:15:42 +0200
Subject: [PATCH 06/11] make interleaving inline, todo optim (2.27us to read
 and decode the adc values from buffer)

---
 src/current/rp2350/RP2350PIOCurrentSense.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/current/rp2350/RP2350PIOCurrentSense.cpp b/src/current/rp2350/RP2350PIOCurrentSense.cpp
index 90aa516..50856a0 100644
--- a/src/current/rp2350/RP2350PIOCurrentSense.cpp
+++ b/src/current/rp2350/RP2350PIOCurrentSense.cpp
@@ -115,7 +115,7 @@
         return 0;
     };
 
-    void extract_bit_interleaved(const uint32_t w0, const uint32_t w1, uint32_t *a, uint32_t *b, uint32_t *c, uint32_t *d) {
+    static inline void extract_bit_interleaved(const uint32_t w0, const uint32_t w1, uint32_t *a, uint32_t *b, uint32_t *c, uint32_t *d) {
         *a = 0;
         *b = 0;
         *c = 0;

From b3730969d4e4b0eb58ba9631cfb43eaba49276b6 Mon Sep 17 00:00:00 2001
From: Thomas Flayols <thomas.flayols@gmail.com>
Date: Thu, 4 Sep 2025 18:54:45 +0200
Subject: [PATCH 07/11] Fix bit order, edge sampling and deinterleaving, First
 working version, validated on RP2350 with 3 ADCs

---
 src/current/rp2350/RP2350PIOCurrentSense.cpp |  4 ++--
 src/current/rp2350/bu79100g_parallel3.pio    |  9 ++++-----
 src/current/rp2350/bu79100g_parallel3.pio.h  | 10 ++++------
 3 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/src/current/rp2350/RP2350PIOCurrentSense.cpp b/src/current/rp2350/RP2350PIOCurrentSense.cpp
index 50856a0..0f6c0ab 100644
--- a/src/current/rp2350/RP2350PIOCurrentSense.cpp
+++ b/src/current/rp2350/RP2350PIOCurrentSense.cpp
@@ -64,7 +64,7 @@
         pio_sm_set_consecutive_pindirs(pio, sm, this->pinD0,  3, false);  // D0..D2 in
 
         // Shift config: right, autopush every 32 bits (two pushes per conversion)
-        sm_config_set_in_shift(&c, true, true, 32);
+        sm_config_set_in_shift(&c, false, true, 32);
 
         // SCK ≈ clk_sys / (2 * clkdiv) because each SCK period = 2 instructions
         float div = (float)clock_get_hz(clk_sys) / (2.0f * sck_hz);
@@ -121,7 +121,7 @@
         *c = 0;
         *d = 0;
         for (int i = 0; i < 64; i += 4) {
-            uint32_t w = (i < 32) ? w1 : w0;
+            uint32_t w = (i < 32) ? w0 : w1;
             int shift = 28 - (i % 32);  // 28, 24, ..., 0 for each group of 4 bits
 
             uint32_t group = (w >> shift) & 0xF;  // extract aN bN cN dN
diff --git a/src/current/rp2350/bu79100g_parallel3.pio b/src/current/rp2350/bu79100g_parallel3.pio
index cb3c52c..b8ca40b 100644
--- a/src/current/rp2350/bu79100g_parallel3.pio
+++ b/src/current/rp2350/bu79100g_parallel3.pio
@@ -17,13 +17,12 @@ dummy_loop:
         nop           side 0          ; SCK=0
         jmp x--, dummy_loop side 1    ; SCK=1
     set pins, 1   side 1       ; CSB=0, keep SCK=HIGH at CSB falling (datasheet rec.)
-    set x, 15     side 1
+    set x, 15     side 1  
     set pins, 0
-    ; -------- 16 real clocks, sample on SCK rising edge -----------
+    ; -------- 16 real clocks, sample on SCK falling edge -----------
 read_loop:    
-        ;nop          side 1  ;DEBUG so we don't have to wait for autopush.
-        in  pins, 4   side 1          ; SCK=1, sample D2..D0 on rising edge  ;Note, Here I had to read 4 pins instead of 3. It seems that with 3, a bit is lost after the first push. Need to read the doc again
-        jmp x--, read_loop side 0      ; SCK=0
+        in  pins, 4   side 0          ; SCK=0, sample D2..D0 on falling edge  ;Note, Here I had to read 4 pins instead of 3. It seems that with 3, a bit is lost after the first push. Need to read the doc again
+        jmp x--, read_loop side 1      ; SCK=1
     ; -------- finish conversion -----------------------------------
     set pins, 1   side 1               ; CSB=1, SCK=1
     ; -------- Pad with 0 ------------------------------------------
diff --git a/src/current/rp2350/bu79100g_parallel3.pio.h b/src/current/rp2350/bu79100g_parallel3.pio.h
index 63f06d5..4208b85 100644
--- a/src/current/rp2350/bu79100g_parallel3.pio.h
+++ b/src/current/rp2350/bu79100g_parallel3.pio.h
@@ -13,7 +13,7 @@
 // ------------------ //
 
 #define bu79100g_parallel3_wrap_target 0
-#define bu79100g_parallel3_wrap 14
+#define bu79100g_parallel3_wrap 12
 #define bu79100g_parallel3_pio_version 1
 
 static const uint16_t bu79100g_parallel3_program_instructions[] = {
@@ -28,18 +28,16 @@ static const uint16_t bu79100g_parallel3_program_instructions[] = {
     0xf801, //  7: set    pins, 1         side 1
     0xf82f, //  8: set    x, 15           side 1
     0xe000, //  9: set    pins, 0
-    0x5804, // 10: in     pins, 4         side 1
-    0x104a, // 11: jmp    x--, 10         side 0
+    0x5004, // 10: in     pins, 4         side 0
+    0x184a, // 11: jmp    x--, 10         side 1
     0xf801, // 12: set    pins, 1         side 1
-    0xe020, // 13: set    x, 0
-    0xa029, // 14: mov    x, ~x
             //     .wrap
 };
 
 #if !PICO_NO_HARDWARE
 static const struct pio_program bu79100g_parallel3_program = {
     .instructions = bu79100g_parallel3_program_instructions,
-    .length = 15,
+    .length = 13,
     .origin = -1,
     .pio_version = bu79100g_parallel3_pio_version,
 #if PICO_PIO_VERSION > 0

From 23859156d15ed8b9711a0cedeb30c35e4f19202e Mon Sep 17 00:00:00 2001
From: Thomas Flayols <thomas.flayols@gmail.com>
Date: Fri, 5 Sep 2025 13:23:56 +0200
Subject: [PATCH 08/11] Optimize de-interleaving (getPhaseCurrents() < 1uS on
 Rp2350), Unroll the loop, only do abc, only 12bits

---
 src/current/rp2350/RP2350PIOCurrentSense.cpp | 51 ++++++++++----------
 1 file changed, 26 insertions(+), 25 deletions(-)

diff --git a/src/current/rp2350/RP2350PIOCurrentSense.cpp b/src/current/rp2350/RP2350PIOCurrentSense.cpp
index 0f6c0ab..8c53612 100644
--- a/src/current/rp2350/RP2350PIOCurrentSense.cpp
+++ b/src/current/rp2350/RP2350PIOCurrentSense.cpp
@@ -115,24 +115,6 @@
         return 0;
     };
 
-    static inline void extract_bit_interleaved(const uint32_t w0, const uint32_t w1, uint32_t *a, uint32_t *b, uint32_t *c, uint32_t *d) {
-        *a = 0;
-        *b = 0;
-        *c = 0;
-        *d = 0;
-        for (int i = 0; i < 64; i += 4) {
-            uint32_t w = (i < 32) ? w0 : w1;
-            int shift = 28 - (i % 32);  // 28, 24, ..., 0 for each group of 4 bits
-
-            uint32_t group = (w >> shift) & 0xF;  // extract aN bN cN dN
-
-            *a = (*a << 1) | ((group >> 0) & 0x1);
-            *b = (*b << 1) | ((group >> 1) & 0x1);
-            *c = (*c << 1) | ((group >> 2) & 0x1);
-            *d = (*d << 1) | ((group >> 3) & 0x1);
-        }
-    }
-
     PhaseCurrent_s RP2350PIOCurrentSense::getPhaseCurrents() {
         PhaseCurrent_s current;
 
@@ -141,16 +123,35 @@
         const uint32_t i_dma = (dma_hw->ch[dma_a].write_addr - base)>>2;
         //For a safe read, get the one that is an even number and at least <2.wi, manage looping
         const uint32_t i_last = (i_dma <= 1) ? RING_WORDS -2 : ((i_dma / 2)*2 - 2);
-        //copy them quickly (before print!)
+        //copy them quickly (before any print!)
         const uint32_t w0 = buff[i_last];
         const uint32_t w1 = buff[i_last+1];
-        //Reconstruct the 3 current from interleaved data
-        uint32_t a,b,c,d = 0;
-        extract_bit_interleaved(w0,w1, &a, &b, &c, &d);    
 
-        current.a = (0x00000fff & a) * gain_a;
-        current.b = (0x00000fff & b) * gain_b;
-        current.c = (0x00000fff & c) * gain_c;
+        //Reconstruct the 3 current from interleaved data
+        uint32_t a,b,c = 0;
+        uint32_t g;
+
+        //g = (w0 >> 28) & 0xFu; a = (a<<1)|((g>>0)&1u); b = (b<<1)|((g>>1)&1u); c = (c<<1)|((g>>2)&1u); d = (d<<1)|((g>>3)&1u);
+        //g = (w0 >> 24) & 0xFu; a = (a<<1)|((g>>0)&1u); b = (b<<1)|((g>>1)&1u); c = (c<<1)|((g>>2)&1u); d = (d<<1)|((g>>3)&1u);
+        //g = (w0 >> 20) & 0xFu; a = (a<<1)|((g>>0)&1u); b = (b<<1)|((g>>1)&1u); c = (c<<1)|((g>>2)&1u); d = (d<<1)|((g>>3)&1u);
+        //g = (w0 >> 16) & 0xFu; a = (a<<1)|((g>>0)&1u); b = (b<<1)|((g>>1)&1u); c = (c<<1)|((g>>2)&1u); d = (d<<1)|((g>>3)&1u);
+        g = (w0 >> 12) & 0xFu; a = (a<<1)|((g>>0)&1u); b = (b<<1)|((g>>1)&1u); c = (c<<1)|((g>>2)&1u);// d = (d<<1)|((g>>3)&1u);
+        g = (w0 >>  8) & 0xFu; a = (a<<1)|((g>>0)&1u); b = (b<<1)|((g>>1)&1u); c = (c<<1)|((g>>2)&1u);// d = (d<<1)|((g>>3)&1u);
+        g = (w0 >>  4) & 0xFu; a = (a<<1)|((g>>0)&1u); b = (b<<1)|((g>>1)&1u); c = (c<<1)|((g>>2)&1u);// d = (d<<1)|((g>>3)&1u);
+        g = (w0 >>  0) & 0xFu; a = (a<<1)|((g>>0)&1u); b = (b<<1)|((g>>1)&1u); c = (c<<1)|((g>>2)&1u);// d = (d<<1)|((g>>3)&1u);
+
+        g = (w1 >> 28) & 0xFu; a = (a<<1)|((g>>0)&1u); b = (b<<1)|((g>>1)&1u); c = (c<<1)|((g>>2)&1u);// d = (d<<1)|((g>>3)&1u);
+        g = (w1 >> 24) & 0xFu; a = (a<<1)|((g>>0)&1u); b = (b<<1)|((g>>1)&1u); c = (c<<1)|((g>>2)&1u);// d = (d<<1)|((g>>3)&1u);
+        g = (w1 >> 20) & 0xFu; a = (a<<1)|((g>>0)&1u); b = (b<<1)|((g>>1)&1u); c = (c<<1)|((g>>2)&1u);// d = (d<<1)|((g>>3)&1u);
+        g = (w1 >> 16) & 0xFu; a = (a<<1)|((g>>0)&1u); b = (b<<1)|((g>>1)&1u); c = (c<<1)|((g>>2)&1u);// d = (d<<1)|((g>>3)&1u);
+        g = (w1 >> 12) & 0xFu; a = (a<<1)|((g>>0)&1u); b = (b<<1)|((g>>1)&1u); c = (c<<1)|((g>>2)&1u);// d = (d<<1)|((g>>3)&1u);
+        g = (w1 >>  8) & 0xFu; a = (a<<1)|((g>>0)&1u); b = (b<<1)|((g>>1)&1u); c = (c<<1)|((g>>2)&1u);// d = (d<<1)|((g>>3)&1u);
+        g = (w1 >>  4) & 0xFu; a = (a<<1)|((g>>0)&1u); b = (b<<1)|((g>>1)&1u); c = (c<<1)|((g>>2)&1u);// d = (d<<1)|((g>>3)&1u);
+        g = (w1 >>  0) & 0xFu; a = (a<<1)|((g>>0)&1u); b = (b<<1)|((g>>1)&1u); c = (c<<1)|((g>>2)&1u);// d = (d<<1)|((g>>3)&1u);
+
+        current.a = a * gain_a;
+        current.b = b * gain_b;
+        current.c = c * gain_c;
         
         return current;
     };

From 2d8b529ffc83d00177d9404ffeff7d01aae738ab Mon Sep 17 00:00:00 2001
From: Thomas Flayols <thomas.flayols@gmail.com>
Date: Mon, 8 Sep 2025 11:38:28 +0200
Subject: [PATCH 09/11] Document the internal design in readme

---
 src/current/rp2350/README.md | 63 +++++++++++++++++++++++++++++++++---
 1 file changed, 59 insertions(+), 4 deletions(-)

diff --git a/src/current/rp2350/README.md b/src/current/rp2350/README.md
index 42e550f..2cdc6f9 100644
--- a/src/current/rp2350/README.md
+++ b/src/current/rp2350/README.md
@@ -14,10 +14,8 @@ Temporarly, for this to work, we need to add a PWM chanell in Arduino-FOC rp2040
 
 
 TODO:
-* Init a the DMA or IRQ to read samples from PIO.
-* Activate the push of adc data in PIO program (disabled for tests)
 * Find a way to setup the trigger PWM from the driver, or change the arduino-foc lib.
-
+* Select an available PIO and state machine automaticaly.
 
 
 # Example:
@@ -58,6 +56,8 @@ void setup() {
 
 void loop() {
   motor.move(target_velocity);
+  PhaseCurrent_s phaseCurrents = curr.getPhaseCurrents();
+  Serial.printf("%d, %3.3lf, %3.3lf, %3.3lf\r\n", micros(), phaseCurrents.a, phaseCurrents.b, phaseCurrents.c);
 }
 ```
 
@@ -69,4 +69,59 @@ Note for self, on my setup:
 ```
 export PIOASM="$HOME/.arduino15/packages/rp2040/tools/pqt-pioasm/4.1.0-1aec55e/pioasm"
 "$PIOASM" -v 1 bu79100g_parallel3.pio bu79100g_parallel3.pio.h
-```
\ No newline at end of file
+```
+
+# Internal Design
+
+This library uses:
+- One PIO state machine  
+- Two DMA channels  
+- One PWM (and associated GPIO)
+
+
+## Trigger Pin
+
+For low-side current measurement, the ADC must sample at the center of the low pulse of the phase PWM signals.  
+To achieve this, a *trigger pin* is configured as an auxiliary PWM output, synchronized with the motor PWM but with a fixed duty cycle.  
+
+- This PWM can be mapped to any pin.  
+- It does **not** need to be connected to external hardware.  
+- The duty cycle is tuned to compensate for the dummy sampling enforced by the BU79100G-LA ADC.  
+
+In the future, this trigger mechanism could also be used to synchronize other types of ADCs.  
+
+**Note (TODO/WIP):** Trigger pin handling is not yet implemented in the driver. Proper synchronization during driver initialization still needs to be added.  
+
+
+## PIO
+
+The PIO waits for a rising edge on the trigger pin to start two SPI transfers:  
+1. A **dummy conversion** (required by the BU79100G-LA when operating at low frequency).  
+2. The **actual ADC conversion**.  
+
+Data is captured from 3 SPI data lines in parallel. A 4th line is also sampled but discarded; it can be freely repurposed as a normal GPIO (input or output).  
+
+The PIO writes results to its FIFO as two interleaved 32-bit words in the format: [a1 b1 c1 d1 a2 b2 c2 d2 .... ]
+
+## DMA
+
+Two DMA channels are configured to move data from the PIO FIFO into system memory:  
+
+- **dma_a** transfers incoming 32-bit words into a ring buffer.  
+  - The buffer size must be a power of two.  
+  - The buffer address must be aligned with its total size.  
+
+- **dma_b** is chained to **dma_a**. It resets the transfer count of **dma_a** by performing a single 32-bit transfer.  
+- **dma_a** is then chained back to **dma_b**, creating a self-sustaining loop without CPU intervention.  
+
+
+## CPU Access to Samples
+
+The CPU can asynchronously access the most recent samples by reading the current DMA write address.  
+
+- If the address is **even**, read samples at positions *n-2* and *n-1*.  
+- If the address is **odd**, read samples at positions *n-3* and *n-2*.  
+- Address wraparound is handled.
+
+Since the PIO delivers interleaved data, the CPU must de-interleave it. On an RP2350, de-interleaving and copying takes approximately **1 µs** per sample set.  
+

From ff1108cdfdf27f8d81278d2c963c239a6ac7f66c Mon Sep 17 00:00:00 2001
From: Thomas Flayols <thomas.flayols@gmail.com>
Date: Thu, 11 Sep 2025 15:31:51 +0200
Subject: [PATCH 10/11] Make pio number a settable parameter, so we can have
 multiple motor using the same PIO with different state machine, ans also be
 compatible with other library that uses other PIOs (encoder for example)

---
 src/current/rp2350/RP2350PIOCurrentSense.cpp | 22 ++++++++++----------
 src/current/rp2350/RP2350PIOCurrentSense.h   |  8 +++----
 2 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/src/current/rp2350/RP2350PIOCurrentSense.cpp b/src/current/rp2350/RP2350PIOCurrentSense.cpp
index 8c53612..092f38f 100644
--- a/src/current/rp2350/RP2350PIOCurrentSense.cpp
+++ b/src/current/rp2350/RP2350PIOCurrentSense.cpp
@@ -1,6 +1,7 @@
     #include "RP2350PIOCurrentSense.h"
 
-    RP2350PIOCurrentSense::RP2350PIOCurrentSense(float gain, uint32_t max_adc_value, int pinSCK, int pinCSB, int pinD0, int pinTRIG) : CurrentSense() {
+    RP2350PIOCurrentSense::RP2350PIOCurrentSense(PIO pio, float gain, uint32_t max_adc_value, int pinSCK, int pinCSB, int pinD0, int pinTRIG) : CurrentSense() {
+        this->pio = pio;
         this->pinSCK = pinSCK;
         this->pinCSB = pinCSB;
         this->pinD0 = pinD0;
@@ -28,12 +29,11 @@
         // TODO init timer to trigger PIO conversions at required frequency (check driver settings)
         //      TDB: do we need config input to know which timer slice and channel to use? or can we pick automatically?
         // TODO start everything up
-
+        // TODO implement offset and calibration like other current sensor classes.
         float sck_hz = 20e6;
-        PIO pio = pio0; 
-        int sm = pio_claim_unused_sm(pio0, true);
+        int sm = pio_claim_unused_sm(this->pio, true);
         //if (sm < 0) { pio = pio1; sm = pio_claim_unused_sm(pio1, true); } //For now, let say we have to use PIO0, this is simpler for quick DMA setup
-
+        
         // --- patch program instructions with chosen trigger pin ---
         size_t prog_len = bu79100g_parallel3_program.length;
         uint16_t insns[prog_len];
@@ -43,7 +43,7 @@
         struct pio_program prog = bu79100g_parallel3_program; // copy metadata
         prog.instructions = insns;
     
-        uint off = pio_add_program(pio, &prog);
+        uint off = pio_add_program(this->pio, &prog);
         pio_sm_config c = bu79100g_parallel3_program_get_default_config(off);
 
         // Map pins to the SM
@@ -52,11 +52,11 @@
         sm_config_set_sideset_pins(&c, this->pinSCK);          // SCK (sideset)
 
         // Put pins into PIO control
-        pio_gpio_init(pio, this->pinSCK);
-        pio_gpio_init(pio, this->pinCSB);
-        pio_gpio_init(pio, this->pinD0);
-        pio_gpio_init(pio, this->pinD1);
-        pio_gpio_init(pio, this->pinD2);
+        pio_gpio_init(this->pio, this->pinSCK);
+        pio_gpio_init(this->pio, this->pinCSB);
+        pio_gpio_init(this->pio, this->pinD0);
+        pio_gpio_init(this->pio, this->pinD1);
+        pio_gpio_init(this->pio, this->pinD2);
 
         // Directions (from the SM’s point of view)
         pio_sm_set_consecutive_pindirs(pio, sm, this->pinSCK, 1, true);   // SCK out
diff --git a/src/current/rp2350/RP2350PIOCurrentSense.h b/src/current/rp2350/RP2350PIOCurrentSense.h
index 0100172..ee7aed7 100644
--- a/src/current/rp2350/RP2350PIOCurrentSense.h
+++ b/src/current/rp2350/RP2350PIOCurrentSense.h
@@ -8,7 +8,7 @@
 
 class RP2350PIOCurrentSense: public CurrentSense {
   public:
-    RP2350PIOCurrentSense(float gain, uint32_t max_adc_value, int pinSCK, int pinCSB, int pinD0, int pinTRIG);
+    RP2350PIOCurrentSense(PIO pio, float gain, uint32_t max_adc_value, int pinSCK, int pinCSB, int pinD0, int pinTRIG);
     ~RP2350PIOCurrentSense();
 
     int init() override;
@@ -27,6 +27,8 @@ class RP2350PIOCurrentSense: public CurrentSense {
     int dma_a = -1; // PIO RX -> ring (streamer)
     int dma_b = -1; // reloader 
 
+    PIO pio;
+
     uint32_t max_adc_value; //!< maximum ADC value (e.g. 4096 for 12 bit ADC)
     int pinCSB;
     int pinSCK;
@@ -34,8 +36,6 @@ class RP2350PIOCurrentSense: public CurrentSense {
     int pinD1;
     int pinD2;
     int pinTRIG;
-    float gain_a;
-    float gain_b;
-    float gain_c;
+
   protected: //For debug, all public
 };

From 488eff6b2a90e21f929f892ca6c874c93ae51f45 Mon Sep 17 00:00:00 2001
From: Thomas Flayols <thomas.flayols@gmail.com>
Date: Thu, 11 Sep 2025 16:32:18 +0200
Subject: [PATCH 11/11] #if defined(ARDUINO_ARCH_RP2040)

---
 src/current/rp2350/RP2350PIOCurrentSense.cpp | 4 ++--
 src/current/rp2350/RP2350PIOCurrentSense.h   | 3 ++-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/current/rp2350/RP2350PIOCurrentSense.cpp b/src/current/rp2350/RP2350PIOCurrentSense.cpp
index 092f38f..8c7a7d7 100644
--- a/src/current/rp2350/RP2350PIOCurrentSense.cpp
+++ b/src/current/rp2350/RP2350PIOCurrentSense.cpp
@@ -1,5 +1,5 @@
     #include "RP2350PIOCurrentSense.h"
-
+    #if defined(ARDUINO_ARCH_RP2040)
     RP2350PIOCurrentSense::RP2350PIOCurrentSense(PIO pio, float gain, uint32_t max_adc_value, int pinSCK, int pinCSB, int pinD0, int pinTRIG) : CurrentSense() {
         this->pio = pio;
         this->pinSCK = pinSCK;
@@ -155,6 +155,6 @@
         
         return current;
     };
-
+    #endif
 
 
diff --git a/src/current/rp2350/RP2350PIOCurrentSense.h b/src/current/rp2350/RP2350PIOCurrentSense.h
index ee7aed7..1b31eeb 100644
--- a/src/current/rp2350/RP2350PIOCurrentSense.h
+++ b/src/current/rp2350/RP2350PIOCurrentSense.h
@@ -1,6 +1,6 @@
 
 #pragma once
-
+#if defined(ARDUINO_ARCH_RP2040)
 #include "common/base_classes/CurrentSense.h"
 #include "bu79100g_parallel3.pio.h"
 #include "hardware/dma.h"
@@ -39,3 +39,4 @@ class RP2350PIOCurrentSense: public CurrentSense {
 
   protected: //For debug, all public
 };
+#endif
\ No newline at end of file