ELM327: incoming messages cleared before commands to prevent congestion.

board/drivers/can.h

@@ -53,6 +53,12 @@ int can_push(can_ring *q, CAN_FIFOMailBox_TypeDef *elem) {
   return ret;
 }
 
+void can_clear(can_ring *q) {
+  enter_critical_section();
+  q->w_ptr = 0;
+  q->r_ptr = 0;
+  exit_critical_section();
+}
 
 // assign CAN numbering
 // bus num: Can bus number on ODB connector. Sent to/from USB
@@ -393,4 +399,3 @@ void can_send(CAN_FIFOMailBox_TypeDef *to_push, uint8_t bus_number) {
 void can_set_forwarding(int from, int to) {
   can_forwarding[from] = to;
 }
-

board/drivers/uart.h

@@ -126,6 +126,15 @@ int putc(uart_ring *q, char elem) {
   return ret;
 }
 
+void clear_uart_buff(uart_ring *q) {
+  enter_critical_section();
+  q->w_ptr_tx = 0;
+  q->r_ptr_tx = 0;
+  q->w_ptr_rx = 0;
+  q->r_ptr_rx = 0;
+  exit_critical_section();
+}
+
 // ***************************** start UART code *****************************
 
 #define __DIV(_PCLK_, _BAUD_)                        (((_PCLK_)*25)/(4*(_BAUD_)))
@@ -146,7 +155,7 @@ void uart_init(USART_TypeDef *u, int baud) {
   // enable uart and tx+rx mode
   u->CR1 = USART_CR1_UE;
   uart_set_baud(u, baud);
-  
+
   u->CR1 |= USART_CR1_TE | USART_CR1_RE;
   //u->CR2 = USART_CR2_STOP_0 | USART_CR2_STOP_1;
   //u->CR2 = USART_CR2_STOP_0;
@@ -213,4 +222,3 @@ void hexdump(const void *a, int l) {
   }
   puts("\n");
 }
-

board/main.c

@@ -117,12 +117,11 @@ int usb_cb_ep1_in(uint8_t *usbdata, int len, int hardwired) {
 
 // send on serial, first byte to select the ring
 void usb_cb_ep2_out(uint8_t *usbdata, int len, int hardwired) {
-  int i;
   if (len == 0) return;
   uart_ring *ur = get_ring_by_number(usbdata[0]);
   if (!ur) return;
   if ((usbdata[0] < 2) || safety_tx_lin_hook(usbdata[0]-2, usbdata+1, len-1)) {
-    for (i = 1; i < len; i++) while (!putc(ur, usbdata[i]));
+    for (int i = 1; i < len; i++) while (!putc(ur, usbdata[i]));
   }
 }
 
@@ -359,6 +358,26 @@ int usb_cb_control_msg(USB_Setup_TypeDef *setup, uint8_t *resp, int hardwired) {
 
       delay(140 * 9000);
       break;
+    // **** 0xf1: Clear CAN ring buffer.
+    case 0xf1:
+      if (setup->b.wValue.w == 0xFFFF) {
+        puts("Clearing CAN Rx queue\n");
+        can_clear(&can_rx_q);
+      } else if (setup->b.wValue.w < BUS_MAX) {
+        puts("Clearing CAN Tx queue\n");
+        can_clear(can_queues[setup->b.wValue.w]);
+      }
+      break;
+    // **** 0xf2: Clear UART ring buffer.
+    case 0xf2:
+      {
+        uart_ring * rb = get_ring_by_number(setup->b.wValue.w);
+        if (rb) {
+          puts("Clearing UART queue.\n");
+          clear_uart_buff(rb);
+        }
+        break;
+      }
     default:
       puts("NO HANDLER ");
       puth(setup->b.bRequest);

boardesp/elm327.c

@@ -213,6 +213,8 @@ static int ICACHE_FLASH_ATTR panda_usbemu_ctrl_write(uint8_t request_type, uint8
 #define panda_set_can0_kbaud(kbps) panda_usbemu_ctrl_write(0x40, 0xde, 0, kbps*10, 0)
 #define panda_set_safety_mode(mode) panda_usbemu_ctrl_write(0x40, 0xdc, mode, 0, 0)
 #define panda_kline_wakeup_pulse() panda_usbemu_ctrl_write(0x40, 0xf0, 0, 0, 0)
+#define panda_clear_can_rx() panda_usbemu_ctrl_write(0x40, 0xf1, 0xFFFF, 0, 0)
+#define panda_clear_lin_txrx() panda_usbemu_ctrl_write(0x40, 0xf2, 2, 0, 0)
 
 static int ICACHE_FLASH_ATTR panda_usbemu_can_read(panda_can_msg_t** can_msgs) {
   int returned_count = spi_comm((uint8_t *)((const uint16 []){1,0}), 4, pandaRecvData, 0x40);
@@ -773,21 +775,12 @@ static void ICACHE_FLASH_ATTR elm_process_obd_cmd_LINFast(const elm_protocol_t*
     return;
   }
 
+  panda_clear_lin_txrx();
+
   if(!lin_bus_initialized) {
     if(!is_auto_detecting)
       elm_append_rsp_const("BUS INIT: ");
 
-    // Kind of a hack to deal with Panda resending data
-    // that could not be sent asap. Try to clear it away.
-    // TODO: A better solution would be to clear out the
-    // CAN mailboxes on the MCU when the speed changes.
-    for(int pass = 0; pass < 32; pass++){
-      int num_can_msgs = panda_usbemu_kline_read(0x40);
-      if(num_can_msgs < 0) continue;
-      if(!num_can_msgs) break;
-      for(int j=0; j<1000; j++) __asm__(""); //Small Delay
-    }
-
     lin_cmd_backup = cmd;
     lin_cmd_backup_len = len;
 
@@ -992,19 +985,6 @@ void ICACHE_FLASH_ATTR elm_ISO15765_timer_cb(void *arg){
 
 static void ICACHE_FLASH_ATTR elm_init_ISO15765(const elm_protocol_t* proto){
   panda_set_can0_cbaud(proto->cbaud);
-
-  // Kind of a hack to deal with Panda resending data
-  // that could not be sent asap. Try to clear it away.
-  // TODO: A better solution would be to clear out the
-  // CAN mailboxes on the MCU when the speed changes.
-  for(int pass = 0; pass < 32; pass++){
-    panda_can_msg_t *can_msgs;
-    int num_can_msgs = panda_usbemu_can_read(&can_msgs);
-    if(num_can_msgs < 0) continue;
-    //if(!num_can_msgs) break;
-    //os_delay_us(1000);
-    for(int j=0; j<1000; j++) __asm__(""); //Small Delay
-  }
 }
 
 static void ICACHE_FLASH_ATTR elm_process_obd_cmd_ISO15765(const elm_protocol_t* proto,
@@ -1031,6 +1011,8 @@ static void ICACHE_FLASH_ATTR elm_process_obd_cmd_ISO15765(const elm_protocol_t*
   os_printf("\n");
   #endif
 
+  panda_clear_can_rx();
+
   panda_usbemu_can_write(0, (proto->type==CAN11) ? 0x7DF : 0x18DB33F1,
                          (uint8_t*)&msg, msg.len+1);
 

panda/__init__.py

@@ -331,6 +331,17 @@ class Panda(object):
         print("CAN: BAD RECV, RETRYING")
     return parse_can_buffer(dat)
 
+  def can_clear(self, bus):
+    """Clears all messages from the specified internal CAN ringbuffer as
+    though it were drained.
+
+    Args:
+      bus (int): can bus number to clear a tx queue, or 0xFFFF to clear the
+        global can rx queue.
+
+    """
+    self._handle.controlWrite(Panda.REQUEST_OUT, 0xf1, bus, 0, b'')
+
   # ******************* serial *******************
 
   def serial_read(self, port_number):
@@ -345,6 +356,16 @@ class Panda(object):
   def serial_write(self, port_number, ln):
     return self._handle.bulkWrite(2, struct.pack("B", port_number) + ln)
 
+  def serial_clear(self, port_number):
+    """Clears all messages (tx and rx) from the specified internal uart
+    ringbuffer as though it were drained.
+
+    Args:
+      port_number (int): port number of the uart to clear.
+
+    """
+    self._handle.controlWrite(Panda.REQUEST_OUT, 0xf2, port_number, 0, b'')
+
   # ******************* kline *******************
 
   # pulse low for wakeup