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.

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;
-};
+};