Revisiting HW vs SW SPI

Dove in to how Hardware vs Software SPI is selected, and realized I was going about the
'SEPARATE' and 'SW' stuff all wrong. Our choices are more-or-less HW SPI on the default
bus, or Software SPI otherwise. I added a config option to force hardware SPI for pins
files that have a SCK/MISO/MOSI defined (i.e. for built-in SoftSPI Thermocouples), and
added separate SoftSPI busses for probes on different busses.

Marlin/Configuration.h

@@ -399,13 +399,18 @@
  *
  * Temperature sensors available:
  *
- * SPI RTD/Thermocouple Boards - NOTE: Ensure TEMP_n_CS_PIN is set in your pins file for each TEMP_SENSOR_n, as well as the
- * ------- following for Software SPI: TEMP_n_MOSI_PIN (MAX31865 only), TEMP_n_MISO_PIN, TEMP_n_SCK_PIN.
+ * SPI RTD/Thermocouple Boards - IMPORTANT: Read the NOTE below!
+ * -------
  * -5 : MAX31865 with Pt100/Pt1000, 2, 3, or 4-wire (only for sensors 0-1)
  * NOTE: You must uncomment/set the MAX31865_*_OHMS_n defines below.
  * -3 : MAX31855 with Thermocouple, -200°C to +700°C (only for sensors 0-1)
  * -2 : MAX6675 with Thermocouple, 0°C to +700°C (only for sensors 0-1)
  *
+ * NOTE: Ensure TEMP_n_CS_PIN is set in your pins file for each TEMP_SENSOR_n using an SPI Thermocouple. By default,
+ * Hardware SPI on the default serial bus is used. If you have also set TEMP_n_SCK_PIN and TEMP_n_MISO_PIN,
+ * Software SPI will be used on those ports instead. You can force Hardware SPI on the default bus in the
+ * Configuration_adv.h file. At this time, separate Hardware SPI buses for sensors are not supported.
+ *
  * Analog Themocouple Boards
  * -------
  * -4 : AD8495 with Thermocouple
@@ -496,10 +501,8 @@
 #define DUMMY_THERMISTOR_999_VALUE 100
 
 // Number of probe wires, and resistor values when using MAX31865 sensors (-5) on TEMP_SENSOR_0 / 1
-//#define MAX31865_SENSOR_WIRES_0 2 // Number of wires the connected probe uses, 2-4 (default: 2)
 //#define MAX31865_SENSOR_OHMS_0 100 // (Ω) Typically 100 or 1000 (PT100 or PT1000)
 //#define MAX31865_CALIBRATION_OHMS_0 430 // (Ω) Typically 430 for Adafruit PT100; 4300 for Adafruit PT1000
-//#define MAX31865_SENSOR_WIRES_1 2
 //#define MAX31865_SENSOR_OHMS_1 100
 //#define MAX31865_CALIBRATION_OHMS_1 430
 

Marlin/Configuration_adv.h

@@ -131,6 +131,17 @@
  #define REDUNDANT_BETA 3950 // Beta value
 #endif
 
+/**
+ * Configuration options for MAX Thermocouples (-2, -3, -5).
+ * FORCE_HW_SPI: Ignore SCK/MOSI/MISO pins and just use the CS pin & default SPI bus.
+ * MAX31865_WIRES: Set the number of wires for the probe connected to a MAX31865 board, 2-4. Default: 2
+ */
+//#define TEMP_SENSOR_0_FORCE_HW_SPI
+//#define TEMP_SENSOR_1_FORCE_HW_SPI
+//#define MAX31865_SENSOR_WIRES_0 2
+//#define MAX31865_SENSOR_WIRES_1 2
+
+
 //
 // Hephestos 2 24V heated bed upgrade kit.
 // https://store.bq.com/en/heated-bed-kit-hephestos2

Marlin/src/inc/Conditionals_post.h

@@ -836,11 +836,11 @@
  #endif
 
  // Software SPI - enable if MISO/SCK are defined.
- #if PIN_EXISTS(TEMP_0_MISO) && PIN_EXISTS(TEMP_0_SCK)
+ #if PIN_EXISTS(TEMP_0_MISO) && PIN_EXISTS(TEMP_0_SCK) && DISABLED(TEMP_SENSOR_0_FORCE_HW_SPI)
  #if TEMP_SENSOR_0_IS_MAX31865 && !PIN_EXISTS(TEMP_0_MOSI)
- #warning "TEMP_SENSOR_0 MAX31865 also needs TEMP_0_MOSI_PIN defined for Software SPI; defaulting to Hardware SPI."
+ #error "TEMP_SENSOR_0 MAX31865 requires TEMP_0_MOSI_PIN defined for Software SPI. To use Hardware SPI instead, undefine MISO/SCK or enable TEMP_SENSOR_0_FORCE_HW_SPI."
  #else
- #define TEMP_SENSOR_0_USES_SW_SPI 1
+ #define TEMP_SENSOR_0_HAS_SPI_PINS 1
  #endif
  #endif
 
@@ -905,11 +905,11 @@
  #endif
 
  // Software SPI - enable if MISO/SCK are defined.
- #if PIN_EXISTS(TEMP_1_MISO) && PIN_EXISTS(TEMP_1_SCK)
+ #if PIN_EXISTS(TEMP_1_MISO) && PIN_EXISTS(TEMP_1_SCK) && DISABLED(TEMP_SENSOR_1_FORCE_HW_SPI)
  #if TEMP_SENSOR_1_IS_MAX31865 && !PIN_EXISTS(TEMP_1_MOSI)
- #warning "TEMP_SENSOR_1 MAX31865 also needs TEMP_1_MOSI_PIN defined for Software SPI; defaulting to Hardware SPI."
+ #error "TEMP_SENSOR_1 MAX31865 requires TEMP_1_MOSI_PIN defined for Software SPI. To use Hardware SPI instead, undefine MISO/SCK or enable TEMP_SENSOR_1_FORCE_HW_SPI."
  #else
- #define TEMP_SENSOR_1_USES_SW_SPI 1
+ #define TEMP_SENSOR_1_HAS_SPI_PINS 1
  #endif
  #endif
 

Marlin/src/module/temperature.cpp

@@ -89,19 +89,29 @@
  #define HAS_MAXTC_LIBRARIES 1
 #endif
 
-// If we have a MAX TC with SCK and MISO pins defined, and we're not using an external library,
-// the MAX TC will be read via Hardware SPI on a different pin.
-#if (TEMP_SENSOR_IS_ANY_MAX_TC(0) && PINS_EXIST(TEMP_0_SCK, TEMP_0_MOSI))
- #define TEMP_SENSOR_0_USES_SEPARATE_SPI 1
-#endif
-#if (TEMP_SENSOR_IS_ANY_MAX_TC(1) && PINS_EXIST(TEMP_1_SCK, TEMP_1_MOSI))
- #define TEMP_SENSOR_1_USES_SEPARATE_SPI 1
+// If we have a MAX TC with SCK and MISO pins defined, it's either on a separate/dedicated Hardware
+// SPI bus, or some pins for Software SPI. Alternate Hardware SPI buses are not supported yet, so
+// your SPI options are:
+//
+// 1. Only CS pin(s) defined: Hardware SPI on the default bus (usually the SD card SPI).
+// 2. CS, MISO, and SCK pins defined: Software SPI on a separate bus, as defined by MISO, SCK.
+// 3. CS, MISO, and SCK pins w/ FORCE_HW_SPI: Hardware SPI on the default bus, ignoring MISO, SCK.
+//
+#if TEMP_SENSOR_IS_ANY_MAX_TC(0) && TEMP_SENSOR_0_HAS_SPI_PINS && DISABLED(TEMP_SENSOR_0_FORCE_HW_SPI)
+ #define TEMP_SENSOR_0_USES_SW_SPI 1
 #endif
+#if TEMP_SENSOR_IS_ANY_MAX_TC(1) && TEMP_SENSOR_1_HAS_SPI_PINS && DISABLED(TEMP_SENSOR_1_FORCE_HW_SPI)
+ #define TEMP_SENSOR_1_USES_SW_SPI 1
 
+ // Two sensors using the same Software SPI bus
+ #if TEMP_SENSOR_0_USES_SW_SPI && TEMP_0_SCK_PIN == TEMP_1_SCK_PIN && TEMP_0_MISO_PIN == TEMP_1_MISO_PIN
+ #define TEMP_SENSOR_SAME_SPI_BUS 1
+ #endif
+#endif
 
-#if TEMP_SENSOR_0_USES_SEPARATE_SPI || TEMP_SENSOR_1_USES_SEPARATE_SPI
+#if TEMP_SENSOR_0_USES_SW_SPI || TEMP_SENSOR_1_USES_SW_SPI
  #include "../libs/private_spi.h"
- #define HAS_MAXTC_SEPARATE_SPI 1
+ #define HAS_MAXTC_SW_SPI 1
 #endif
 
 #if ENABLED(PID_EXTRUSION_SCALING)
@@ -189,13 +199,22 @@ const char str_t_thermal_runaway[] PROGMEM = STR_T_THERMAL_RUNAWAY,
 //
 #if HAS_MAX_TC
 
- #if HAS_MAXTC_SEPARATE_SPI
- //TODO: what about multi_tc?
- template<uint8_t MisoPin, uint8_t MosiPin, uint8_t SckPin> SoftSPI<MisoPin, MosiPin, SckPin> SPIclass<MisoPin, MosiPin, SckPin>::softSPI;
- SPIclass<TEMP_0_MISO_PIN, SD_MOSI_PIN, TEMP_0_SCK_PIN> max_tc_spi;
+ #if !HAS_MAXTC_LIBRARIES
+ // Initialize SoftSPI for non-lib Software SPI; Libraries take care of it themselves.
+ #if TEMP_SENSOR_0_USES_SW_SPI
+ template<uint8_t MisoPin, uint8_t MosiPin, uint8_t SckPin> SoftSPI<MisoPin, MosiPin, SckPin> SPIclass<MisoPin, MosiPin, SckPin>::softSPI;
+ SPIclass<TEMP_0_MISO_PIN, SD_MOSI_PIN, TEMP_0_SCK_PIN> max_tc_spi_0;
+ #endif
+ #if TEMP_SENSOR_1_USES_SW_SPI
+ #if TEMP_SENSOR_SAME_SPI_BUS
+ SPIclass &max_tc_spi_1 = max_tc_spi_0;
+ #else
+ template<uint8_t MisoPin, uint8_t MosiPin, uint8_t SckPin> SoftSPI<MisoPin, MosiPin, SckPin> SPIclass<MisoPin, MosiPin, SckPin>::softSPI;
+ SPIclass<TEMP_1_MISO_PIN, SD_MOSI_PIN, TEMP_1_SCK_PIN> max_tc_spi_1;
+ #endif
+ #endif
  #endif
 
-
  #define MAXTC_INIT(n, M) \
  MAX##M max##M##_##n = MAX##M( \
  TEMP_##n##_CS_PIN \
@@ -226,6 +245,7 @@ const char str_t_thermal_runaway[] PROGMEM = STR_T_THERMAL_RUNAWAY,
  #endif
 
  // MAX31865 always uses a library, unlike '55 & 6675
+ // FIXME: The MAX31865 lib should use SoftSPI/MarlinSerial instead of SPI/raw pin manipulation
  #if HAS_MAX31865
  #define _MAX31865_0_SW TEMP_SENSOR_0_USES_SW_SPI
  #define _MAX31865_1_SW TEMP_SENSOR_1_USES_SW_SPI
@@ -2189,8 +2209,13 @@ void Temperature::init() {
  INIT_FAN_PIN(CONTROLLER_FAN_PIN);
  #endif
 
- #if HAS_MAXTC_SEPARATE_SPI
- max_tc_spi.init();
+ #if !HAS_MAXTC_LIBRARIES
+ #if TEMP_SENSOR_0_USES_SW_SPI
+ max_tc_spi_0.init();
+ #endif
+ #if TEMP_SENSOR_1_USES_SW_SPI && !TEMP_SENSOR_SAME_SPI_BUS
+ max_tc_spi_1.init();
+ #endif
  #endif
 
  HAL_adc_init();
@@ -2618,21 +2643,29 @@ void Temperature::disable_all_heaters() {
  static celsius_t max_tc_temp_previous[MAX_TC_COUNT] = { 0 };
  #define THERMO_TEMP(I) max_tc_temp_previous[I]
  #define THERMO_SEL(A,B) (hindex ? (B) : (A))
- #define MAXTC_WRITE(V) do{ switch (hindex) { case 1: WRITE(TEMP_1_CS_PIN, V); break; default: WRITE(TEMP_0_CS_PIN, V); } }while(0)
+ #define MAXTC_CS_WRITE(V) do{ switch (hindex) { case 1: WRITE(TEMP_1_CS_PIN, V); break; default: WRITE(TEMP_0_CS_PIN, V); } }while(0)
  #else
  // When we have only 1 max tc, THERMO_SEL will pick the appropriate sensor
  // variable, and MAXTC_*() macros will be hardcoded to the correct CS pin.
  constexpr uint8_t hindex = 0;
  #define THERMO_TEMP(I) max_tc_temp
  #if TEMP_SENSOR_IS_ANY_MAX_TC(0)
  #define THERMO_SEL(A,B) A
- #define MAXTC_WRITE(V) WRITE(TEMP_0_CS_PIN, V)
+ #define MAXTC_CS_WRITE(V) WRITE(TEMP_0_CS_PIN, V)
  #else
  #define THERMO_SEL(A,B) B
- #define MAXTC_WRITE(V) WRITE(TEMP_1_CS_PIN, V)
+ #define MAXTC_CS_WRITE(V) WRITE(TEMP_1_CS_PIN, V)
  #endif
  #endif
 
+ #if TEMP_SENSOR_0_USES_SW_SPI && TEMP_SENSOR_1_USES_SW_SPI
+ #define THERMO_SPI_SEL(A,B) (hindex ? (B) : (A))
+ #elif TEMP_SENSOR_0_USES_SW_SPI
+ #define THERMO_SPI_SEL(A,B) A
+ #elif TEMP_SENSOR_1_USES_SW_SPI
+ #define THERMO_SPI_SEL(A,B) B
+ #endif
+
  static uint8_t max_tc_errors[MAX_TC_COUNT] = { 0 };
 
  // Return last-read value between readings
@@ -2644,25 +2677,30 @@ void Temperature::disable_all_heaters() {
  max_tc_temp = 0;
 
  #if !HAS_MAXTC_LIBRARIES
- #if !HAS_MAXTC_SEPARATE_SPI
- // Initialize SPI using the default SPI bus.
+ #if !HAS_MAXTC_SW_SPI
+ // Initialize SPI using the default Hardware SPI bus.
  // FIXME: spiBegin, spiRec and spiInit doesn't work when soft spi is used.
  spiBegin();
  spiInit(MAX_TC_SPEED_BITS);
  #endif
 
- // Read a big-endian temperature value without using a library
- MAXTC_WRITE(LOW); // enable MAXTC
- DELAY_NS(100); // Ensure 100ns delay
+ MAXTC_CS_WRITE(LOW); // enable MAXTC
+ DELAY_NS(100); // Ensure 100ns delay
 
+ // Read a big-endian temperature value without using a library
  for (uint8_t i = sizeof(max_tc_temp); i--;) {
- max_tc_temp |= TERN(HAS_MAXTC_SEPARATE_SPI, max_tc_spi.receive(), spiRec());
+ max_tc_temp |= (
+ #if HAS_MAXTC_SW_SPI
+ THERMO_SPI_SEL(max_tc_spi_0, max_tc_spi_1).receive()
+ #else
+ spiRec()
+ #endif
+ );
  if (i > 0) max_tc_temp <<= 8; // shift left if not the last byte
  }
 
- MAXTC_WRITE(HIGH); // disable MAXTC
+ MAXTC_CS_WRITE(HIGH); // disable MAXTC
  #else
- // TODO: a lot of this is references to the GadgetAngel ModM versions...
  #if HAS_MAX6675_LIBRARY
  MAX6675 &max6675ref = THERMO_SEL(max6675_0, max6675_1);
  max_tc_temp = max6675ref.readRaw16();