ch32v: Revamp the board-level usart setup design

examples/raspberrypi/rp2xxx/src/uart_echo.zig

@@ -38,7 +38,7 @@ pub fn main() !void {
             continue;
         };
 
-        //tries to write one byte with 100ms timeout
+        // Try to write one byte with 100ms timeout
         _ = uart.write_blocking(&data, time.deadline_in_ms(100)) catch {
             uart.clear_errors();
         };

examples/wch/ch32v/build.zig

@@ -37,11 +37,14 @@ pub fn build(b: *std.Build) void {
         .{ .target = mb.ports.ch32v.chips.ch32v203x6, .name = "blinky_systick_ch32v203", .file = "src/blinky_systick.zig" },
         .{ .target = mb.ports.ch32v.boards.ch32v203.nano_ch32v203, .name = "nano_ch32v203_blinky", .file = "src/board_blinky.zig" },
         .{ .target = mb.ports.ch32v.boards.ch32v203.nano_ch32v203, .name = "nano_ch32v203_blinky_wfe", .file = "src/blinky_wfe.zig" },
+        .{ .target = mb.ports.ch32v.boards.ch32v203.nano_ch32v203, .name = "nano_ch32v203_uart_echo", .file = "src/uart_echo.zig" },
+        .{ .target = mb.ports.ch32v.boards.ch32v203.nano_ch32v203, .name = "nano_ch32v203_uart_log", .file = "src/uart_log.zig" },
         .{ .target = mb.ports.ch32v.boards.ch32v203.nano_ch32v203, .name = "nano_ch32v203_usb_cdc", .file = "src/usb_cdc.zig" },
         .{ .target = mb.ports.ch32v.boards.ch32v203.suzuduino_uno_v1b, .name = "suzuduino_blinky", .file = "src/board_blinky.zig" },
         .{ .target = mb.ports.ch32v.boards.ch32v203.suzuduino_uno_v1b, .name = "suzuduino_usb_cdc", .file = "src/usb_cdc.zig" },
         .{ .target = mb.ports.ch32v.boards.ch32v203.lana_tny, .name = "lana_tny_dma", .file = "src/dma.zig" },
         .{ .target = mb.ports.ch32v.boards.ch32v203.lana_tny, .name = "lana_tny_ws2812", .file = "src/ws2812.zig" },
+        .{ .target = mb.ports.ch32v.boards.ch32v203.lana_tny, .name = "lana_tny_uart_echo", .file = "src/uart_echo.zig" },
         .{ .target = mb.ports.ch32v.boards.ch32v203.lana_tny, .name = "lana_tny_uart_log", .file = "src/uart_log.zig" },
         .{ .target = mb.ports.ch32v.boards.ch32v203.lana_tny, .name = "lana_tny_i2c_bus_scan", .file = "src/i2c_bus_scan.zig" },
         .{ .target = mb.ports.ch32v.boards.ch32v203.lana_tny, .name = "lana_tny_i2c_eeprom", .file = "src/i2c_eeprom.zig" },

examples/wch/ch32v/src/uart_echo.zig

@@ -0,0 +1,31 @@
+const microzig = @import("microzig");
+
+const hal = microzig.hal;
+const board = microzig.board;
+const time = hal.time;
+
+const uart = board.uart_setup;
+
+pub const panic = microzig.panic;
+
+pub const std_options = microzig.std_options(.{});
+
+comptime {
+    _ = microzig.export_startup();
+}
+
+pub fn main() !void {
+    board.init();
+
+    uart.apply(.{ .baud_rate = 115200 });
+
+    const usart = uart.instance;
+
+    var data: [1]u8 = .{0};
+    while (true) {
+        usart.read_blocking(&data, .no_deadline) catch {
+            continue;
+        };
+        _ = usart.write_blocking(&data, time.deadline_in_ms(100)) catch {};
+    }
+}

examples/wch/ch32v/src/uart_log.zig

@@ -4,7 +4,7 @@ const hal = microzig.hal;
 const board = microzig.board;
 const time = hal.time;
 
-const uart_cfg: hal.usart.UartConfig = if (@hasDecl(board, "uart_config")) board.uart_config else .{};
+const uart = board.uart_setup;
 
 pub const panic = microzig.panic;
 
@@ -20,8 +20,8 @@ comptime {
 pub fn main() !void {
     board.init();
 
-    hal.usart.setup_uart(uart_cfg);
-    hal.usart.init_logger(uart_cfg.instance);
+    uart.apply(.{ .baud_rate = 115200 });
+    hal.usart.init_logger(uart.instance);
 
     var i: u32 = 0;
     while (true) : (i += 1) {

port/wch/ch32v/src/boards/LANA_TNY.zig

@@ -21,9 +21,10 @@ pub fn init() void {
 }
 
 /// Default UART: USART2 on PA2 (exposed on the board header)
-pub const uart_config: ch32v.usart.UartConfig = .{
+pub const uart_setup: ch32v.usart.UartSetup = .{
     .instance = .USART2,
     .tx_pin = ch32v.gpio.Pin.init(0, 2), // PA2
+    .rx_pin = ch32v.gpio.Pin.init(0, 3), // PA3
 };
 
 pub const pin_config = ch32v.pins.GlobalConfiguration{

port/wch/ch32v/src/boards/nanoCH32V203.zig

@@ -25,7 +25,11 @@ pub fn init() void {
 }
 
 /// Default UART: USART1 on PA9
-pub const uart_config: ch32v.usart.UartConfig = .{};
+pub const uart_setup: ch32v.usart.UartSetup = .{
+    .instance = .USART1,
+    .tx_pin = ch32v.gpio.Pin.init(0, 9), // PA9
+    .rx_pin = ch32v.gpio.Pin.init(0, 10), // PA10
+};
 
 pub const pin_config = ch32v.pins.GlobalConfiguration{
     .GPIOA = .{

port/wch/ch32v/src/hals/time.zig

@@ -176,3 +176,11 @@ pub fn delay_us(us: u32) void {
         asm volatile ("" ::: .{ .memory = true });
     }
 }
+
+pub fn deadline_in_ms(time_ms: u32) microzig.drivers.time.Deadline {
+    return .init_relative(get_time_since_boot(), .from_ms(time_ms));
+}
+
+pub fn deadline_in_us(time_us: u64) microzig.drivers.time.Deadline {
+    return .init_relative(get_time_since_boot(), .from_us(time_us));
+}

port/wch/ch32v/src/hals/usart.zig

@@ -92,24 +92,26 @@ pub const ReceiveError = error{
 
 const gpio = hal.gpio;
 
-/// Configuration for board-level UART defaults.
-/// Boards export a `uart_config` const of this type with their preferred
-/// USART instance, TX pin, and serial settings. Examples can use these
-/// defaults directly or construct their own `UartConfig`.
-pub const UartConfig = struct {
-    instance: USART = .USART1,
-    tx_pin: gpio.Pin = gpio.Pin.init(0, 9), // PA9 (USART1 default TX)
-    config: Config = .{ .baud_rate = 115200 },
+/// Physical-layer UART setup: which USART instance and pins to use.
+/// Boards export a `uart_setup` const of this type. Application-level
+/// settings (baud rate, parity, etc.) are passed separately via `Config`.
+pub const UartSetup = struct {
+    instance: USART,
+    tx_pin: ?gpio.Pin = null,
+    rx_pin: ?gpio.Pin = null,
+
+    /// Apply settings: configure whichever pins are present, then apply
+    /// the USART peripheral config (clock, baud rate, etc.).
+    pub fn apply(comptime self: UartSetup, comptime config: Config) void {
+        if (self.tx_pin) |tx| tx.configure_alternate_function(.push_pull, .max_50MHz);
+        if (self.rx_pin) |rx| {
+            rx.enable_clock();
+            rx.set_input_mode(.floating);
+        }
+        self.instance.apply(config);
+    }
 };
 
-/// Configure a UART from a `UartConfig`: sets up the TX pin as alternate
-/// function push-pull, then applies the USART peripheral configuration
-/// (clock enable, AFIO remap, baud rate, etc.).
-pub fn setup_uart(comptime cfg: UartConfig) void {
-    cfg.tx_pin.configure_alternate_function(.push_pull, .max_50MHz);
-    cfg.instance.apply(cfg.config);
-}
-
 pub const instance = struct {
     pub const USART1: USART = .USART1;
     pub const USART2: USART = .USART2;