cdc_acm: turn on UART_TX LED when sending break signals

Software typically asserts line break for an extended period (e.g. PuTTY will assert continuously until the next keypress), so provide feedback via the LED. Also declare variables used in both tinyusb callback and uart_thread context as volatile.

Author: P33M

src/cdc_uart.c

@@ -32,8 +32,9 @@
 #include "probe_config.h"
 
 TaskHandle_t uart_taskhandle;
-TickType_t last_wake, interval = 100, break_expiry;
-bool timed_break;
+TickType_t last_wake, interval = 100;
+volatile TickType_t break_expiry;
+volatile bool timed_break;
 
 /* Max 1 FIFO worth of data */
 static uint8_t tx_buf[32];
@@ -43,7 +44,7 @@ static uint8_t rx_buf[32];
 static uint debounce_ticks = 5;
 
 #ifdef PROBE_UART_TX_LED
-static uint tx_led_debounce;
+static volatile uint tx_led_debounce;
 #endif
 
 #ifdef PROBE_UART_RX_LED
@@ -145,6 +146,7 @@ bool cdc_task(void)
  if (((int)break_expiry - (int)xTaskGetTickCount()) < 0) {
  timed_break = false;
  uart_set_break(PROBE_UART_INTERFACE, false);
+ tx_led_debounce = 0;
  } else {
  keep_alive = true;
  }
@@ -154,6 +156,7 @@ bool cdc_task(void)
  uart_set_break(PROBE_UART_INTERFACE, false);
  timed_break = false;
  was_connected = 0;
+ tx_led_debounce = 0;
  cdc_tx_oe = 0;
  }
  return keep_alive;
@@ -275,11 +278,15 @@ void tud_cdc_send_break_cb(uint8_t itf, uint16_t wValue) {
  case 0xffff:
  uart_set_break(PROBE_UART_INTERFACE, true);
  timed_break = false;
+ gpio_put(PROBE_UART_TX_LED, 1);
+ tx_led_debounce = 1 << 30;
  break;
  default:
  uart_set_break(PROBE_UART_INTERFACE, true);
  timed_break = true;
+ gpio_put(PROBE_UART_TX_LED, 1);
  break_expiry = xTaskGetTickCount() + (wValue * (configTICK_RATE_HZ / 1000));
+ tx_led_debounce = 1 << 30;
  break;
  }
 }