make baud rate configurable

firmware/rust1/src/rs485.rs

@@ -3,6 +3,7 @@ use embassy_futures::select::*;
 use embassy_rp::gpio;
 use embassy_rp::pac;
 use embassy_rp::interrupt::UART0_IRQ;
+use embassy_rp::uart::Parity;
 use embassy_time::{Duration, Timer};
 use embassy_embedded_hal::SetConfig;
 use embassy_rp::peripherals::{self, UART0};
@@ -12,6 +13,8 @@ use embassy_rp::relocate::RelocatedProgram;
 use embassy_rp::Peripheral;
 use {defmt_rtt as _, panic_probe as _};
 use fixed::traits::ToFixed;
+use fixed::types::U24F8;
+use fixed::types::U56F8;
 use fixed_macro::types::U56F8;
 use futures::Future;
 
@@ -37,6 +40,8 @@ pub struct RS485<H: RS485Handler> {
     dma_channel: peripherals::DMA_CH0,
     tx_dma_channel: peripherals::DMA_CH2,
     rx: UartRx<'static, UART0, uart::Async>,
+    uart_baud_rate: u32,
+    uart_parity: Parity,
     handler: H
 }
 
@@ -90,7 +95,13 @@ impl<H: RS485Handler> RS485<H> {
             rx_dma_channel,
             uart_config,
         );
-        RS485 { pio, rx_pin: rx_pin_for_autobaud, tx_pin, tx_en_pin, dma_channel, tx_dma_channel, rx: uart_rx, handler }
+        RS485 {
+            pio, rx_pin: rx_pin_for_autobaud, tx_pin, tx_en_pin, dma_channel, tx_dma_channel,
+            rx: uart_rx,
+            uart_baud_rate: uart_config.baudrate,
+            uart_parity: uart_config.parity,
+            handler,
+        }
     }
 
     pub async fn run_task(mut self: Self) {
@@ -208,8 +219,9 @@ impl<H: RS485Handler> RS485<H> {
         let mut cfg = Config::default();
         let loaded_program = common.load_program(&relocated);
         cfg.use_program(&loaded_program, &[]);
+        const CPU_CLK: u32 = 125_000_000;
         const SM_FREQ: u32 = 25_000_000;
-        cfg.clock_divider = (U56F8!(125_000_000) / U56F8!(25_000_000 /* SM_FREQ */)).to_fixed();
+        cfg.clock_divider = U24F8::from_num(CPU_CLK / SM_FREQ);
         cfg.shift_in = ShiftConfig {
             auto_fill: true,
             threshold: 32,
@@ -230,7 +242,10 @@ impl<H: RS485Handler> RS485<H> {
         // Timeout: Modbus wants 3.5 char times between frames but we should detect the end of a frame
         // after 1.5 char times. This is 0.86 ms at 19200 baud (8e1, i.e. 11 baud times per char).
         // We need two clocks for each loop.
-        let timeout_start_value = (SM_FREQ as f32 * 0.86e-3 / 2.) as u32;
+        //let timeout_start_value = (SM_FREQ as f32 * 0.86e-3 / 2.) as u32;
+        let symbols_per_byte = if self.uart_parity == Parity::ParityNone { 10 } else { 11 };
+        let timeout_seconds = 1.5 * symbols_per_byte as f32 * 1000. / self.uart_baud_rate as f32;
+        let timeout_start_value = (SM_FREQ as f32 * timeout_seconds / 2.) as u32;
         sm.tx().push(timeout_start_value);
         info!("timeout_start_value: {} = 0x{:08x}", timeout_start_value, timeout_start_value);
 
@@ -264,8 +279,7 @@ impl<H: RS485Handler> RS485<H> {
         let tx_en_pin_pio = common.make_pio_pin(self.tx_en_pin);
         let loaded_program = common.load_program(&relocated);
         cfg.use_program(&loaded_program, &[&tx_en_pin_pio, &tx_pin_pio]);
-        const BAUD_RATE: u32 = 19200;
-        cfg.clock_divider = (U56F8!(125_000_000) / U56F8!(76800 /* BAUD_RATE*4 */)).to_fixed();
+        cfg.clock_divider = (U56F8::from_num(CPU_CLK) / U56F8::from_num(self.uart_baud_rate*4)).to_fixed();
         cfg.shift_out = ShiftConfig {
             auto_fill: false,
             threshold: 32,