Implement chunked SPI transfer for ch341 (#3847)

This seems to fix the ch341 quirk where large packets fail to send. As it can be problematic for other radios, we gate it behind "ch341_quirk" in the config.

bin/config-dist.yaml

@@ -52,6 +52,8 @@ Lora:
 #  TXen: x  # TX and RX enable pins
 #  RXen: x
 
+#  ch341_quirk: true # Uncomment this to use the chunked SPI transfer that seems to fix the ch341
+
 ### Set gpio chip to use in /dev/. Defaults to 0.
 ### Notably the Raspberry Pi 5 puts the GPIO header on gpiochip4
 #  gpiochip: 4

src/main.cpp

@@ -738,7 +738,8 @@ void setup()
     if (settingsMap[use_sx1262]) {
         if (!rIf) {
             LOG_DEBUG("Attempting to activate sx1262 radio on SPI port %s\n", settingsStrings[spidev].c_str());
-            LockingArduinoHal *RadioLibHAL = new LockingArduinoHal(SPI, spiSettings);
+            LockingArduinoHal *RadioLibHAL =
+                new LockingArduinoHal(SPI, spiSettings, (settingsMap[ch341Quirk] ? settingsMap[busy] : RADIOLIB_NC));
             rIf = new SX1262Interface((LockingArduinoHal *)RadioLibHAL, settingsMap[cs], settingsMap[irq], settingsMap[reset],
                                       settingsMap[busy]);
             if (!rIf->init()) {
@@ -752,7 +753,8 @@ void setup()
     } else if (settingsMap[use_rf95]) {
         if (!rIf) {
             LOG_DEBUG("Attempting to activate rf95 radio on SPI port %s\n", settingsStrings[spidev].c_str());
-            LockingArduinoHal *RadioLibHAL = new LockingArduinoHal(SPI, spiSettings);
+            LockingArduinoHal *RadioLibHAL =
+                new LockingArduinoHal(SPI, spiSettings, (settingsMap[ch341Quirk] ? settingsMap[busy] : RADIOLIB_NC));
             rIf = new RF95Interface((LockingArduinoHal *)RadioLibHAL, settingsMap[cs], settingsMap[irq], settingsMap[reset],
                                     settingsMap[busy]);
             if (!rIf->init()) {

src/mesh/RadioLibInterface.cpp

@@ -25,7 +25,31 @@ void LockingArduinoHal::spiEndTransaction()
 #if ARCH_PORTDUINO
 void LockingArduinoHal::spiTransfer(uint8_t *out, size_t len, uint8_t *in)
 {
-    spi->transfer(out, in, len);
+    if (busy == RADIOLIB_NC) {
+        spi->transfer(out, in, len);
+    } else {
+        uint16_t offset = 0;
+
+        while (len) {
+            uint8_t block_size = (len < 20 ? len : 20);
+            spi->transfer((out != NULL ? out + offset : NULL), (in != NULL ? in + offset : NULL), block_size);
+            if (block_size == len)
+                return;
+
+            // ensure GPIO is low
+
+            uint32_t start = millis();
+            while (digitalRead(busy)) {
+                if (millis() - start >= 2000) {
+                    LOG_ERROR("GPIO mid-transfer timeout, is it connected?");
+                    return;
+                }
+            }
+
+            offset += block_size;
+            len -= block_size;
+        }
+    }
 }
 #endif
 
@@ -414,4 +438,4 @@ void RadioLibInterface::startSend(meshtastic_MeshPacket *txp)
         // bits
         enableInterrupt(isrTxLevel0);
     }
-}
+}

src/mesh/RadioLibInterface.h

@@ -21,12 +21,20 @@
 class LockingArduinoHal : public ArduinoHal
 {
   public:
-    LockingArduinoHal(SPIClass &spi, SPISettings spiSettings) : ArduinoHal(spi, spiSettings){};
+    LockingArduinoHal(SPIClass &spi, SPISettings spiSettings, RADIOLIB_PIN_TYPE _busy = RADIOLIB_NC)
+        : ArduinoHal(spi, spiSettings)
+    {
+#if ARCH_PORTDUINO
+        busy = _busy;
+#endif
+    };
 
     void spiBeginTransaction() override;
     void spiEndTransaction() override;
 #if ARCH_PORTDUINO
+    RADIOLIB_PIN_TYPE busy;
     void spiTransfer(uint8_t *out, size_t len, uint8_t *in) override;
+
 #endif
 };
 
@@ -179,4 +187,4 @@ class RadioLibInterface : public RadioInterface, protected concurrency::Notified
     virtual void addReceiveMetadata(meshtastic_MeshPacket *mp) = 0;
 
     virtual void setStandby() = 0;
-};
+};

src/platform/portduino/PortduinoGlue.cpp

@@ -168,6 +168,7 @@ void portduinoSetup()
             settingsMap[txen] = yamlConfig["Lora"]["TXen"].as<int>(RADIOLIB_NC);
             settingsMap[rxen] = yamlConfig["Lora"]["RXen"].as<int>(RADIOLIB_NC);
             settingsMap[gpiochip] = yamlConfig["Lora"]["gpiochip"].as<int>(0);
+            settingsMap[ch341Quirk] = yamlConfig["Lora"]["ch341_quirk"].as<bool>(false);
             gpioChipName += std::to_string(settingsMap[gpiochip]);
 
             settingsStrings[spidev] = "/dev/" + yamlConfig["Lora"]["spidev"].as<std::string>("spidev0.0");

src/platform/portduino/PortduinoGlue.h

@@ -11,6 +11,7 @@ enum configNames {
     rxen,
     dio2_as_rf_switch,
     dio3_tcxo_voltage,
+    ch341Quirk,
     use_rf95,
     use_sx1280,
     use_sx1268,