Apply v1.0's upstream DMA workaround to v0.9. So it seems that under

some circumstances the 405 is equally buggy as the 401!

Work around an intermittent stall/timeout by busy-waiting Upstream's
packet length transmission and reception, instead of DMA-ing it like the
packet body. Ugh...

Upstream/Drivers/STM32F4xx_HAL_Driver/Inc/stm32f4xx_hal_spi.h

@@ -302,6 +302,8 @@ typedef struct __SPI_HandleTypeDef
   * @}
   */
 
+#define SPI_TIMEOUT_VALUE  2
+
 /**
   * @}
   */

Upstream/Drivers/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal_spi.c

@@ -104,7 +104,6 @@
 
 /* Private typedef -----------------------------------------------------------*/
 /* Private define ------------------------------------------------------------*/
-#define SPI_TIMEOUT_VALUE  2
 /* Private macro -------------------------------------------------------------*/
 /* Private variables ---------------------------------------------------------*/
 /* Private function prototypes -----------------------------------------------*/

Upstream/Src/upstream_spi.c

@@ -442,13 +442,16 @@ void Upstream_BeginTransmitPacketSize(void)
 {
     UpstreamInterfaceState = UPSTREAM_INTERFACE_TX_SIZE;
     SPI1_NSS_ASSERT;
-    if (HAL_SPI_TransmitReceive_DMA(&Hspi1,
+    if (HAL_SPI_TransmitReceive(&Hspi1,
                                     (uint8_t*)&CurrentWorkingPacket->Length16,
                                     (uint8_t*)&TemporaryIncomingPacketLength,
-                                    2) != HAL_OK)       //We only need to write one word, but the peripheral library freaks out...
+                                    2,
+                                    SPI_TIMEOUT_VALUE) != HAL_OK)       //We only need to write one word, but the peripheral library freaks out...
     {
         UPSTREAM_SPI_FREAKOUT;
     }
+
+    HAL_SPI_TxRxCpltCallback(&Hspi1);
 }
 
 
@@ -485,13 +488,16 @@ void Upstream_BeginReceivePacketSize(UpstreamPacketTypeDef* freePacket)
     CurrentWorkingPacket = freePacket;
     CurrentWorkingPacket->Length16 = 0;     //Our RX buffer is used by HAL_SPI_TransmitReceive_DMA as dummy TX data, we set Length to 0 so downstream will know this is a dummy packet.
     SPI1_NSS_ASSERT;
-    if (HAL_SPI_TransmitReceive_DMA(&Hspi1,
+    if (HAL_SPI_TransmitReceive(&Hspi1,
                                     (uint8_t*)&CurrentWorkingPacket->Length16,
                                     (uint8_t*)&CurrentWorkingPacket->Length16,
-                                    2) != HAL_OK)       //We only need to write one word, but the peripheral library freaks out...
+                                    2,
+                                    SPI_TIMEOUT_VALUE) != HAL_OK)       //We only need to write one word, but the peripheral library freaks out...
     {
         UPSTREAM_SPI_FREAKOUT;
     }
+
+    HAL_SPI_TxRxCpltCallback(&Hspi1);
 }