From c4980f435704a0f70f258d6a2639a73f2cdb92bb Mon Sep 17 00:00:00 2001
From: Graziano Misuraca <grazfather@gmail.com>
Date: Sat, 25 Jul 2026 09:55:01 -0400
Subject: [PATCH] wip: board-specific uart and other config

This is an attempt to make examples more generic, but putting more of
the board-specific config (e.g. which pins are easy to use for uart) in
a board file, while still providing an easy way for it to be overridden.
---
 examples/wch/ch32v/src/uart_log.zig        | 32 ++++------------------
 port/wch/ch32v/src/boards/LANA_TNY.zig     |  6 ++++
 port/wch/ch32v/src/boards/nanoCH32V203.zig |  3 ++
 port/wch/ch32v/src/hals/usart.zig          | 20 ++++++++++++++
 4 files changed, 34 insertions(+), 27 deletions(-)

diff --git a/examples/wch/ch32v/src/uart_log.zig b/examples/wch/ch32v/src/uart_log.zig
index cb2bc7dc8..3d5328ac9 100644
--- a/examples/wch/ch32v/src/uart_log.zig
+++ b/examples/wch/ch32v/src/uart_log.zig
@@ -1,14 +1,10 @@
 const std = @import("std");
 const microzig = @import("microzig");
 const hal = microzig.hal;
+const board = microzig.board;
 const time = hal.time;
-const gpio = hal.gpio;
 
-const RCC = microzig.chip.peripherals.RCC;
-const AFIO = microzig.chip.peripherals.AFIO;
-
-const usart = hal.usart.instance.USART2;
-const usart_tx_pin = gpio.Pin.init(0, 2); // PA2
+const uart_cfg: hal.usart.UartConfig = if (@hasDecl(board, "uart_config")) board.uart_config else .{};
 
 pub const panic = microzig.panic;
 
@@ -22,28 +18,10 @@ comptime {
 }
 
 pub fn main() !void {
-    // Board brings up clocks and time
-    microzig.board.init();
-
-    // Enable peripheral clocks for USART2 and GPIOA
-    RCC.APB2PCENR.modify(.{
-        .IOPAEN = 1, // Enable GPIOA clock
-        .AFIOEN = 1, // Enable AFIO clock
-    });
-    RCC.APB1PCENR.modify(.{
-        .USART2EN = 1, // Enable USART2 clock
-    });
-
-    // Ensure USART2 is NOT remapped (default PA2/PA3, not PD5/PD6)
-    AFIO.PCFR1.modify(.{ .USART2_RM = 0 });
-
-    // Configure PA2 as alternate function push-pull for USART2 TX
-    usart_tx_pin.set_output_mode(.alternate_function_push_pull, .max_50MHz);
-
-    // Initialize USART2 at 115200 baud
-    usart.apply(.{ .baud_rate = 115200 });
+    board.init();
 
-    hal.usart.init_logger(usart);
+    hal.usart.setup_uart(uart_cfg);
+    hal.usart.init_logger(uart_cfg.instance);
 
     var i: u32 = 0;
     while (true) : (i += 1) {
diff --git a/port/wch/ch32v/src/boards/LANA_TNY.zig b/port/wch/ch32v/src/boards/LANA_TNY.zig
index c4c744018..832767d1e 100644
--- a/port/wch/ch32v/src/boards/LANA_TNY.zig
+++ b/port/wch/ch32v/src/boards/LANA_TNY.zig
@@ -20,6 +20,12 @@ pub fn init() void {
     ch32v.time.init();
 }
 
+/// Default UART: USART2 on PA2 (exposed on the board header)
+pub const uart_config: ch32v.usart.UartConfig = .{
+    .instance = .USART2,
+    .tx_pin = ch32v.gpio.Pin.init(0, 2), // PA2
+};
+
 pub const pin_config = ch32v.pins.GlobalConfiguration{
     .GPIOD = .{
         .PIN0 = .{
diff --git a/port/wch/ch32v/src/boards/nanoCH32V203.zig b/port/wch/ch32v/src/boards/nanoCH32V203.zig
index 79a2815da..c69aa5481 100644
--- a/port/wch/ch32v/src/boards/nanoCH32V203.zig
+++ b/port/wch/ch32v/src/boards/nanoCH32V203.zig
@@ -24,6 +24,9 @@ pub fn init() void {
     ch32v.clocks.enable_usbfs_clock();
 }
 
+/// Default UART: USART1 on PA9
+pub const uart_config: ch32v.usart.UartConfig = .{};
+
 pub const pin_config = ch32v.pins.GlobalConfiguration{
     .GPIOA = .{
         .PIN15 = .{
diff --git a/port/wch/ch32v/src/hals/usart.zig b/port/wch/ch32v/src/hals/usart.zig
index a6fc86c1d..bb15b97ea 100644
--- a/port/wch/ch32v/src/hals/usart.zig
+++ b/port/wch/ch32v/src/hals/usart.zig
@@ -90,6 +90,26 @@ pub const ReceiveError = error{
     Timeout,
 };
 
+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 },
+};
+
+/// 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;