Changed PTT behaviour from RTS&-DTR to just DTR to enable use of certain applications.

For unwanted assertion of the PTT (e.g. in CHIRP), an additional safeguard has been implemented that disables all PTT action whenever a character is sent to the radio. For a lengthy discussion see #11.

stm32/aioc-fw/Src/usb_serial.c

@@ -5,6 +5,37 @@
 #include "led.h"
 #include "usb_descriptors.h"
 
+static void ControlPTT(uint8_t ptt1, uint8_t ptt2)
+{
+    if (ptt1 || ptt2) {
+        /* In case any PTT is asserted, disable UART transmitter due to those sharing the same lines */
+        USB_SERIAL_UART->CR1 &= (uint32_t) ~USART_CR1_TE;
+    }
+
+    if (ptt1) {
+        /* PTT1 */
+        USB_SERIAL_UART_GPIO->BSRR |= USB_SERIAL_UART_PIN_PTT1;
+        LED_SET(1, 1);
+    } else {
+        USB_SERIAL_UART_GPIO->BRR |= USB_SERIAL_UART_PIN_PTT1;
+        LED_SET(1, 0);
+    }
+
+    if (ptt2) {
+        /* PTT2 */
+        USB_SERIAL_UART_GPIO->BSRR |= USB_SERIAL_UART_PIN_PTT2;
+        LED_SET(0, 1);
+    } else {
+        USB_SERIAL_UART_GPIO->BRR |= USB_SERIAL_UART_PIN_PTT2;
+        LED_SET(0, 0);
+    }
+
+    if (!ptt1 && !ptt2) {
+        /* Enable UART transmitter again, when no PTT is asserted */
+        USB_SERIAL_UART->CR1 |= USART_CR1_TE;
+    }
+}
+
 void USB_SERIAL_UART_IRQ(void)
 {
     uint32_t ISR = USB_SERIAL_UART->ISR;
@@ -73,6 +104,9 @@ void tud_cdc_rx_cb(uint8_t itf)
         /* This enables the transmitter and the TX-empty interrupt, which handles writing UART data */
         __disable_irq();
         USB_SERIAL_UART->CR1 |= USART_CR1_TE | USART_CR1_TXEIE;
+
+        /* Disable all PTT action */
+        ControlPTT(0, 0);
         __enable_irq();
     }
 }
@@ -145,39 +179,17 @@ void tud_cdc_line_coding_cb(uint8_t itf, cdc_line_coding_t const* p_line_coding)
 // Invoked when cdc when line state changed e.g connected/disconnected
 void tud_cdc_line_state_cb(uint8_t itf, bool dtr, bool rts)
 {
-    if (dtr ^ rts) {
-        /* In case any PTT is asserted, disable UART transmitter due to those sharing the same lines */
-        __disable_irq();
-        USB_SERIAL_UART->CR1 &= (uint32_t) ~USART_CR1_TE;
-        __enable_irq();
-    }
-
-    if (!dtr & rts) {
-        /* PTT1 */
-        USB_SERIAL_UART_GPIO->BSRR |= USB_SERIAL_UART_PIN_PTT1;
-        LED_SET(1, 1);
-    } else {
-        USB_SERIAL_UART_GPIO->BRR |= USB_SERIAL_UART_PIN_PTT1;
-        LED_SET(1, 0);
-    }
-
+    /* PTT Encoding logic */
+    uint8_t ptt1 = dtr;
 #if AIOC_ENABLE_PTT2
-    if (dtr & !rts) {
-        /* PTT2 */
-        USB_SERIAL_UART_GPIO->BSRR |= USB_SERIAL_UART_PIN_PTT2;
-        LED_SET(0, 1);
-    } else {
-        USB_SERIAL_UART_GPIO->BRR |= USB_SERIAL_UART_PIN_PTT2;
-        LED_SET(0, 0);
-    }
+    uint8_t ptt2 = rts;
+#else
+    uint8_t ptt2 = 0;
 #endif
 
-    if ( !(dtr ^ rts) ) {
-        /* Enable UART transmitter again, when no PTT is asserted */
-        __disable_irq();
-        USB_SERIAL_UART->CR1 |= USART_CR1_TE;
-        __enable_irq();
-    }
+    __disable_irq();
+    ControlPTT(ptt1, ptt2);
+    __enable_irq();
 }
 
 void USB_SerialInit(void)