Add hardware flow and line control

CMakeLists.txt

@@ -2,6 +2,8 @@
 
 cmake_minimum_required(VERSION 3.13)
 
+option(FLOW_CONTROL "Enable Hardware Flow-control on the UARTs" FALSE)
+
 include(pico-sdk/pico_sdk_init.cmake)
 
 project(pico_uart_bridge)
@@ -19,4 +21,12 @@ target_link_libraries(uart_bridge
 	pico_stdlib
 	tinyusb_device)
 
+if(FLOW_CONTROL)
+target_compile_definitions(uart_bridge PUBLIC FLOW_CONTROL=1)
+endif()
+
+if(LINE_CONTROL)
+target_compile_definitions(uart_bridge PUBLIC LINE_CONTROL=1)
+endif()
+
 pico_add_extra_outputs(uart_bridge)

README.md

@@ -11,9 +11,45 @@ This software is provided without warranty, according to the MIT License, and sh
 Raspberry Pi Pico Pinout
 ------------------------
 
-| Raspberry Pi Pico GPIO | Function |
-|:----------------------:|:--------:|
-| GPIO0 (Pin 1)          | UART0 TX |
-| GPIO1 (Pin 2)          | UART0 RX |
-| GPIO4 (Pin 6)          | UART1 TX |
-| GPIO5 (Pin 7)          | UART1 RX |
+UART0:
+| Raspberry Pi Pico GPIO | Function  |
+|:----------------------:|:---------:|
+| GPIO0 (Pin 1)          | TX        |
+| GPIO1 (Pin 2)          | RX        |
+| GPIO2 (Pin 4)          | CTS       |
+| GPIO3 (Pin 5)          | RTS       |
+| GPIO4 (Pin 6)          | DTR       |
+| GPIO5 (Pin 7)          | DSR       |
+
+UART1:
+| Raspberry Pi Pico GPIO | Function  |
+|:----------------------:|:---------:|
+| GPIO8  (Pin 11)        | TX        |
+| GPIO9  (Pin 12)        | RX        |
+| GPIO10 (Pin 14)        | CTS       |
+| GPIO11 (Pin 15)        | RTS       |
+| GPIO12 (Pin 16)        | DTR       |
+| GPIO13 (Pin 17)        | DSR       |
+
+Optional Hardware Flow and Line control
+------------------------------
+
+Hardware Flow-control (RTS/CTS) is disabled by default, but can be compiled in by running:
+
+``` bash
+cmake -DFLOW_CONTROL .
+make
+```
+
+Line control (DTR/DSR) is disabled by default, but can be compiled in by running:
+
+``` bash
+cmake -DLINE_CONTROL .
+make
+```
+
+To enable both:
+``` bash
+cmake -DLINE_CONTROL -DFLOW_CONTROL .
+make
+```

uart-bridge.c

@@ -28,6 +28,14 @@ typedef struct {
 	uart_inst_t *const inst;
 	uint8_t tx_pin;
 	uint8_t rx_pin;
+#ifdef FLOW_CONTROL
+	uint8_t rts_pin;
+	uint8_t cts_pin;
+#endif
+#ifdef LINE_CONTROL
+	uint8_t dtr_pin;
+	uint8_t dsr_pin;
+#endif
 } uart_id_t;
 
 typedef struct {
@@ -47,10 +55,26 @@ const uart_id_t UART_ID[CFG_TUD_CDC] = {
 		.inst = uart0,
 		.tx_pin = 0,
 		.rx_pin = 1,
+#ifdef FLOW_CONTROL
+		.cts_pin = 2,
+		.rts_pin = 3,
+#endif
+#ifdef LINE_CONTROL
+		.dtr_pin = 4,
+		.dsr_pin = 5,
+#endif
 	}, {
 		.inst = uart1,
-		.tx_pin = 4,
-		.rx_pin = 5,
+		.tx_pin = 8,
+		.rx_pin = 9,
+#ifdef FLOW_CONTROL
+		.cts_pin = 10,
+		.rts_pin = 11,
+#endif
+#ifdef LINE_CONTROL
+		.dtr_pin = 12,
+		.dsr_pin = 13,
+#endif
 	}
 };
 
@@ -233,6 +257,17 @@ void init_uart_data(uint8_t itf) {
 	/* Pinmux */
 	gpio_set_function(ui->tx_pin, GPIO_FUNC_UART);
 	gpio_set_function(ui->rx_pin, GPIO_FUNC_UART);
+#ifdef FLOW_CONTROL
+	gpio_set_function(ui->rts_pin, GPIO_FUNC_UART);
+	gpio_set_function(ui->cts_pin, GPIO_FUNC_UART);
+#endif
+
+#ifdef LINE_CONTROL
+	gpio_init(ui->dtr_pin);
+	gpio_set_dir(ui->dtr_pin, GPIO_OUT);
+	gpio_init(ui->dsr_pin);
+	gpio_set_dir(ui->dsr_pin, GPIO_IN);
+#endif
 
 	/* USB CDC LC */
 	ud->usb_lc.bit_rate = DEF_BIT_RATE;
@@ -257,12 +292,26 @@ void init_uart_data(uint8_t itf) {
 
 	/* UART start */
 	uart_init(ui->inst, ud->usb_lc.bit_rate);
+#ifdef FLOW_CONTROL
+	uart_set_hw_flow(ui->inst, true, true);
+#else
 	uart_set_hw_flow(ui->inst, false, false);
+#endif
 	uart_set_format(ui->inst, databits_usb2uart(ud->usb_lc.data_bits),
 			stopbits_usb2uart(ud->usb_lc.stop_bits),
 			parity_usb2uart(ud->usb_lc.parity));
 }
 
+#ifdef LINE_CONTROL
+/* Invoked when line state has changed */
+void tud_cdc_line_state_cb(uint8_t itf, bool dtr, bool rts)
+{
+	const uart_id_t *ui = &UART_ID[itf];
+
+	gpio_put(ui->dtr_pin, dtr);
+}
+#endif
+
 int main(void)
 {
 	int itf;