Allow loading custom waveforms via sysex

Source/io/midi.c

@@ -1,6 +1,7 @@
 #include "midi.h"
 #include "../mGB.h"
 #include "midi_asm.h"
+#include "midi_sysex.h"
 #include "serial.h"
 
 uint8_t statusByte;
@@ -17,8 +18,17 @@ void updateMidiBuffer(void) {
 
   uint8_t byte = serialBuffer[serialBufferReadPosition];
 
+  if (sysexBytesCount) {
+    captureSysexByte(byte);
+    return;
+  }
+
   // STATUS BYTE
   if (byte & MIDI_STATUS_BIT) {
+    if (byte == MIDI_STATUS_SYSEX) {
+      sysexBytesCount = 1;
+      return;
+    }
     if ((byte & MIDI_STATUS_SYSTEM) == MIDI_STATUS_SYSTEM) {
       return;
     }

Source/io/midi.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <gbdk/platform.h>
+#include <stdbool.h>
 
 #define MIDI_STATUS_BIT 0x80
 #define MIDI_STATUS_NOTE_ON 0x09

Source/io/midi_sysex.c

@@ -0,0 +1,84 @@
+#include "midi_sysex.h"
+#include "../mGB.h"
+
+uint8_t sysexBytesCount;
+sysex_payload_t sysexPayload;
+uint8_t sysexBuffer[24];
+
+// adapted from
+// https://github.com/FortySevenEffects/arduino_midi_library/blob/2d64cc3c2ff85bbee654a7054e36c59694d8d8e4/src/MIDI.cpp#L87
+// (MIT licensed)
+// Reduced parameter count to improve perf
+
+/*!
+ \brief Decode System Exclusive messages.
+
+ SysEx messages are encoded to guarantee transmission of data bytes higher
+ than 127 without breaking the MIDI protocol. Use this static method to
+ reassemble your received message.
+
+ \param outData The output buffer where to
+ store the decrypted message.
+ \param inLength The length of the input
+ buffer.
+ \return The length of the output buffer.
+ @see encodeSysEx @see getSysExArrayLength
+ Code inspired from Ruin & Wesen's SysEx encoder/decoder - http://ruinwesen.com
+ */
+static uint8_t decodeSysEx(uint8_t *outData, uint8_t inLength) {
+  uint8_t count = 0;
+  uint8_t msbStorage = 0;
+  uint8_t byteIndex = 0;
+
+  for (uint8_t i = 0; i < inLength; ++i) {
+    if ((i % 8) == 0) {
+      msbStorage = sysexBuffer[i];
+      byteIndex = 6;
+    } else {
+      const uint8_t body = sysexBuffer[i];
+      const uint8_t msb = (((msbStorage >> byteIndex) & 1) << 7);
+      byteIndex--;
+      outData[count++] = msb | body;
+    }
+  }
+  return count;
+}
+
+void captureSysexByte(uint8_t byte) {
+  sysexBytesCount++;
+  systemIdle = false;
+
+  const uint8_t bufferIndex = sysexBytesCount - SYSEX_HEADER_SIZE;
+
+  if (byte == SYSEX_EOF) {
+    // EMU_printf("sysex EOF: %#02x\n", byte);
+    sysexPayload.size = decodeSysEx(&sysexPayload.data[0], bufferIndex);
+    sysexPayload.ready = true;
+    sysexBytesCount = 0;
+    return;
+  }
+
+  switch (sysexBytesCount) {
+  case 1:
+    // EMU_printf("sysex status byte: %#02x\n", byte);
+    // ignored in payload
+    break;
+  case 2:
+    // EMU_printf("sysex id: %#02x\n", byte);
+    sysexPayload.id = byte;
+    break;
+  case 3:
+    // EMU_printf("sysex device_id: %#02x\n", byte);
+    sysexPayload.device_id = byte;
+    break;
+  case 4:
+    // EMU_printf("sysex channel: %#02x\n", byte);
+    sysexPayload.channel = byte;
+    break;
+
+  default:
+    // EMU_printf("sysex data: %#02x\n", byte);
+    sysexBuffer[bufferIndex] = byte;
+    break;
+  }
+}

Source/io/midi_sysex.h

@@ -0,0 +1,46 @@
+#pragma once
+
+#include <gbdk/platform.h>
+#include <stdbool.h>
+
+#define MIDI_STATUS_SYSEX 0xF0
+#define SYSEX_UNIVERSAL_REALTIME 0x7F
+#define SYSEX_UNIVERSAL_NON_REALTIME 0x7E
+#define SYSEX_NON_COMMERCIAL 0x7D
+#define SYSEX_EOF 0xF7
+
+#define SYSEX_MGB_ID 0x69
+
+// The size of the SysEx message header before the payload begins
+#define SYSEX_HEADER_SIZE 5
+
+extern uint8_t sysexBytesCount;
+
+typedef struct sysex_payload {
+  // the sysex message id (or manufacturer id)
+  uint8_t id;
+  // the payload device id (0xBB for mGB)
+  uint8_t device_id;
+  // the device or channel id
+  uint8_t channel;
+  // the size of the data
+  uint8_t size;
+  // the data payload (24 raw sysex bytes = 21 (3*7) + 3 header blocks)
+  uint8_t data[21];
+  // true if the payload has finished reading from the buffer (has seen an EOF)
+  bool ready;
+} sysex_payload_t;
+
+// A SysEx payload, captures up to 16 bytes of sysex data. Currently this is
+// used to modify the active WAV channel waveform.
+extern sysex_payload_t sysexPayload;
+
+// The buffer to hold the sysexBytes before decoding
+// contains enough space to hold 16 bytes = MSB, 7 bytes, MSB, 7 bytes, MSB, 2
+// bytes = 19 bytes
+extern uint8_t sysexBuffer[24];
+
+// Reads SysEx messages (F0) up until a SysEx EOF packet
+// (F7). Data is stored in `sysexPayload` and will set `sysexPayload.ready` when
+// it sees the EOF
+void captureSysexByte(uint8_t byte);

Source/io/sram.c

@@ -2,7 +2,9 @@
 #include "../mGB.h"
 #include "../screen/main.h"
 #include "../synth/data.h"
+#include "../synth/wav.h"
 #include <gbdk/platform.h>
+#include <string.h>
 
 void saveDataSet(uint8_t synth) {
   // EMU_printf("saveDataSet(synth %d)\n", synth);
@@ -80,41 +82,76 @@ void loadDataSet(uint8_t synth) {
   DISABLE_RAM_MBC1;
 }
 
-void checkMemory(void) {
+// Init V1 SRAM data (`saveData`)
+static void initV1(void) {
+  for (x = 0; x != 128; x += 8) {
+    l = 0;
+    for (i = 0; i < 7; i++) {
+      saveData[(x + l)] = dataSet[i];
+      l++;
+    }
+    l = 0;
+    for (i = 7; i != 13; i++) {
+      saveData[(x + 128U + l)] = dataSet[i];
+      l++;
+    }
+    l = 0;
+    for (i = 13; i != 20; i++) {
+      saveData[(x + 256U + l)] = dataSet[i];
+      l++;
+    }
+    l = 0;
+    for (i = 20; i != 24; i++) {
+      saveData[(x + 384U + l)] = dataSet[i];
+      l++;
+    }
+  }
+  saveData[SRAM_SENTINEL_INDEX] = SRAM_INITIALIZED;
+  sram_version = 1;
+}
+
+// Init V2 SRAM data (`sram_wavData`)
+static void initV2(void) {
+  memcpy(&sram_wavData, &wavData, sizeof(sram_wavData));
+  sram_version = 2;
+}
+
+// load the SRAM `sram_wavData` data into the runtime `wavData`
+static void sramLoadAllWavData(void) {
+  memcpy(&wavData, &sram_wavData, sizeof(wavData));
+}
+
+void initMemory(void) {
   ENABLE_RAM_MBC1;
 
   // fixes some SRAM Bugs
   SWITCH_ROM(1);
   SWITCH_RAM(0);
   // end fix
 
-  if (saveData[512] != SRAM_INITIALIZED) {
-    for (x = 0; x != 128; x += 8) {
-      l = 0;
-      for (i = 0; i < 7; i++) {
-        saveData[(x + l)] = dataSet[i];
-        l++;
-      }
-      l = 0;
-      for (i = 7; i != 13; i++) {
-        saveData[(x + 128U + l)] = dataSet[i];
-        l++;
-      }
-      l = 0;
-      for (i = 13; i != 20; i++) {
-        saveData[(x + 256U + l)] = dataSet[i];
-        l++;
-      }
-      l = 0;
-      for (i = 20; i != 24; i++) {
-        saveData[(x + 384U + l)] = dataSet[i];
-        l++;
-      }
-    }
-    saveData[512] = SRAM_INITIALIZED;
+  if (sram_version == 2) {
+    // do nothing
+  } else if (saveData[SRAM_SENTINEL_INDEX] == SRAM_INITIALIZED) {
+    // legacy SRAM format (== V1)
+    initV2();
+  } else {
+    // no SRAM initialized
+    saveData[SRAM_SENTINEL_INDEX] = SRAM_INITIALIZED;
+    initV1();
+    initV2();
   }
+
+  sramLoadAllWavData();
   DISABLE_RAM_MBC1;
 
   for (j = 0; j != 24; j++)
     dataSetSnap[j] = dataSet[j];
 }
+
+void sramStoreWaveform(uint8_t index) {
+  const uint8_t offset = index * WAVEFORM_LENGTH;
+
+  ENABLE_RAM_MBC1;
+  memcpy(&sram_wavData[offset], &wavData[offset], WAVEFORM_LENGTH);
+  DISABLE_RAM_MBC1;
+}

Source/io/sram.h

@@ -2,11 +2,26 @@
 
 #include <gbdk/platform.h>
 
+// the position in SRAM where the Version sentinel sits
+#define SRAM_SENTINEL_INDEX 512
+
+// SRAM sentinel value to determine if anything is initialized
 #define SRAM_INITIALIZED 0xF7
 
 // 512 + sentinel
-extern uint8_t saveData[513U];
+extern volatile uint8_t saveData[513];
+
+// SRAM version, so that we can determine if a partial migration/init is needed
+extern volatile uint8_t sram_version;
+
+// SRAM stored wav data, can be modified at runtime
+extern volatile uint8_t sram_wavData[256];
 
 void saveDataSet(uint8_t synth);
 void loadDataSet(uint8_t synth);
-void checkMemory(void);
+
+// initialises the SRAM
+void initMemory(void);
+
+// Copies a wave from `wavData` into SRAM stored `sram_wavData`
+void sramStoreWaveform(uint8_t index);

Source/io/sram/sram.b0.c

@@ -2,4 +2,10 @@
 
 #include <gbdk/platform.h>
 
-uint8_t saveData[513];
+uint8_t saveData[513];
+
+// SRAM version
+uint8_t sram_version;
+
+// SRAM stored wav data, can be modified at runtime
+uint8_t sram_wavData[256];

Source/mGB.c

@@ -42,7 +42,7 @@ void main(void) {
 
   CRITICAL {
     cpu_fast();
-    checkMemory();
+    initMemory();
     displaySetup();
     initMainScreen();
     setSoundDefaults();

Source/mGB.h

@@ -1,5 +1,6 @@
 #pragma once
 
+// #include <gbdk/emu_debug.h>
 #include <gbdk/platform.h>
 #include <stdbool.h>
 

Source/synth/common.c

@@ -139,6 +139,7 @@ void updateSynths(void) {
     updateVibratoPosition(NOI);
 
   updateWavSweep();
+  updateWavSysex();
 }
 
 inline void setOutputSwitch(void) {