probe: handle pipelined OUT transfers properly

A consequence of tinyUSB's implementation of vendor interfaces is that
it treats pipe traffic as free-flowing, i.e. no distinction is made if a
short packet is received. CMSIS-DAP should ordinarily encapsulate a set
of commands in a single packet, but if multiple packets are receieved
before the FIFO is drained then all the commands need to be processed at
once.

Ensure there is always enough RX space, and TX space for the generated
response.

include/DAP_config.h

@@ -62,7 +62,6 @@ This information includes:
 /// a Cortex-M0+ processor with high-speed peripheral I/O only 1 processor cycle might be
 /// required.
 #define IO_PORT_WRITE_CYCLES    1U              ///< I/O Cycles: 2=default, 1=Cortex-M0+ fast I/0.
-#define DELAY_SLOW_CYCLES 1U // We don't differentiate between fast/slow, we've got a 16-bit divisor for that
 
 /// Indicate that Serial Wire Debug (SWD) communication mode is available at the Debug Access Port.
 /// This information is returned by the command \ref DAP_Info as part of <b>Capabilities</b>.
@@ -95,7 +94,7 @@ This information includes:
 /// This configuration settings is used to optimize the communication performance with the
 /// debugger and depends on the USB peripheral. For devices with limited RAM or USB buffer the
 /// setting can be reduced (valid range is 1 .. 255).
-#define DAP_PACKET_COUNT        2U              ///< Specifies number of packets buffered.
+#define DAP_PACKET_COUNT        3U              ///< Specifies number of packets buffered.
 
 /// Indicate that UART Serial Wire Output (SWO) trace is available.
 /// This information is returned by the command \ref DAP_Info as part of <b>Capabilities</b>.

src/main.c

@@ -32,20 +32,20 @@
 #include <string.h>
 
 #include "bsp/board.h"
-#include "tusb.h"
 
-#include "picoprobe_config.h"
-#include "probe.h"
+#include "tusb.h"
+#include "time.h"
 #include "cdc_uart.h"
 #include "get_serial.h"
 #include "led.h"
 #include "DAP.h"
+#include "DAP_config.h"
 
 // UART0 for Picoprobe debug
 // UART1 for picoprobe to target device
 
-static uint8_t TxDataBuffer[CFG_TUD_HID_EP_BUFSIZE];
-static uint8_t RxDataBuffer[CFG_TUD_HID_EP_BUFSIZE];
+static uint8_t TxDataBuffer[CFG_TUD_HID_EP_BUFSIZE * DAP_PACKET_COUNT];
+static uint8_t RxDataBuffer[CFG_TUD_HID_EP_BUFSIZE * DAP_PACKET_COUNT];
 
 #define THREADED 1
 
@@ -66,16 +66,29 @@ void usb_thread(void *ptr)
 
 void dap_thread(void *ptr)
 {
-    uint32_t resp_len;
+    uint32_t ret;
+    int32_t packet_len;
+    uint16_t req_len, resp_len;
+    uint8_t *rx_ptr;
+
     do {
-        if (tud_vendor_available()) {
-            tud_vendor_read(RxDataBuffer, sizeof(RxDataBuffer));
-            resp_len = DAP_ProcessCommand(RxDataBuffer, TxDataBuffer);
-            tud_vendor_write(TxDataBuffer, resp_len);
-        } else {
-            // Trivial delay to save power
-            vTaskDelay(2);
+        while (tud_vendor_available()) {
+            rx_ptr = &RxDataBuffer[0];
+            packet_len = tud_vendor_read(rx_ptr, sizeof(RxDataBuffer));
+            picoprobe_debug("Got chunk %u\n", packet_len);
+            do {
+                ret = DAP_ProcessCommand(rx_ptr, TxDataBuffer);
+                resp_len = ret & 0xffff;
+                req_len = ret >> 16;
+                tud_vendor_write(TxDataBuffer, resp_len);
+                rx_ptr += req_len;
+                packet_len -= req_len;
+                picoprobe_debug("Packet decode remaining %u req %u resp %u\n",
+                                packet_len, req_len, resp_len);
+            } while (packet_len > 0);
         }
+        // Trivial delay to save power
+        vTaskDelay(1);
     } while (1);
 }