From e729db5942f8853a08a1b8ef22703b7e83a8af44 Mon Sep 17 00:00:00 2001
From: narvalotech <jonathan@rico.live>
Date: Thu, 28 Apr 2022 09:29:32 +0200
Subject: [PATCH] Add hardware flow-control

---
 CMakeLists.txt |  6 ++++++
 README.md      | 26 ++++++++++++++++++++------
 uart-bridge.c  | 20 ++++++++++++++++++++
 3 files changed, 46 insertions(+), 6 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index eda4f18..72c2301 100644
--- a/CMakeLists.txt
+++ b/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 +21,8 @@ target_link_libraries(uart_bridge
 	pico_stdlib
 	tinyusb_device)
 
+if(FLOW_CONTROL)
+target_compile_definitions(uart_bridge PUBLIC FLOW_CONTROL=1)
+endif()
+
 pico_add_extra_outputs(uart_bridge)
diff --git a/README.md b/README.md
index c6a3967..c3c5436 100644
--- a/README.md
+++ b/README.md
@@ -11,9 +11,23 @@ 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 |
+| Raspberry Pi Pico GPIO | Function  |
+|:----------------------:|:---------:|
+| GPIO0 (Pin 1)          | UART0 TX  |
+| GPIO1 (Pin 2)          | UART0 RX  |
+| GPIO2 (Pin 4)          | UART0 CTS |
+| GPIO3 (Pin 5)          | UART0 RTS |
+| GPIO4 (Pin 6)          | UART1 TX  |
+| GPIO5 (Pin 7)          | UART1 RX  |
+| GPIO6 (Pin 9)          | UART1 CTS |
+| GPIO7 (Pin 10)         | UART1 RTS |
+
+Optional Hardware Flow-control
+------------------------------
+
+Hardware Flow-control is disabled by default, but can be compiled in by running:
+
+``` bash
+cmake -DFLOW_CONTROL .
+make
+```
diff --git a/uart-bridge.c b/uart-bridge.c
index aebbdf6..a472299 100644
--- a/uart-bridge.c
+++ b/uart-bridge.c
@@ -28,6 +28,10 @@ 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
 } uart_id_t;
 
 typedef struct {
@@ -47,10 +51,18 @@ 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
 	}, {
 		.inst = uart1,
 		.tx_pin = 4,
 		.rx_pin = 5,
+#ifdef FLOW_CONTROL
+		.cts_pin = 6,
+		.rts_pin = 7,
+#endif
 	}
 };
 
@@ -233,6 +245,10 @@ 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
 
 	/* USB CDC LC */
 	ud->usb_lc.bit_rate = DEF_BIT_RATE;
@@ -257,7 +273,11 @@ 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));