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uart: add baud_rate_gen

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This commit is contained in:
Astro 2019-05-22 01:42:00 +02:00
parent 43b6d3acd0
commit b296fc1d7f
2 changed files with 47 additions and 8 deletions
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43
src/uart/baud_rate_gen.rs Normal file
View File

@ -0,0 +1,43 @@
use crate::regs::*;
use super::regs::{RegisterBlock, BaudRateGen, BaudRateDiv};
const BDIV_MIN: u8 = 4;
const BDIV_MAX: u8 = 255;
const CD_MAX: u16 = 65535;
/// Algorithm as in the Linux 5.1 driver
pub fn configure(regs: &RegisterBlock, mut clk: u32, baud: u32) {
if regs.mode.read().clks() {
clk /= 8;
}
let mut best = None;
for bdiv in BDIV_MIN..=BDIV_MAX {
let bdiv: u32 = bdiv.into();
let cd = clk / (baud * (bdiv + 1));
if cd < 1 || cd > CD_MAX.into() {
continue;
}
let actual_baud = clk / (cd * (bdiv + 1));
let error = if baud > actual_baud {
baud - actual_baud
} else {
actual_baud - baud
};
let better = best
.map(|(_cd, _bdiv, best_error)| error < best_error)
.unwrap_or(true);
if better {
best = Some((cd as u16, bdiv as u8, error));
}
}
match best {
Some((cd, bdiv, error)) => {
regs.baud_rate_gen.write(BaudRateGen::zeroed().cd(cd));
regs.baud_rate_divider.write(BaudRateDiv::zeroed().bdiv(bdiv));
}
None => panic!("Cannot configure baud rate")
}
}

12
src/uart/mod.rs
View File

@ -6,6 +6,7 @@ use volatile_register::RW;
use crate::regs::*;
mod regs;
mod baud_rate_gen;
pub struct Uart {
regs: &'static mut regs::RegisterBlock,
@ -49,12 +50,12 @@ impl Uart {
}
pub fn configure(&self) {
// Confiugre UART character frame
// Configure UART character frame
// * Disable clock-divider
// * 8-bit
// * 1 stop bit
// * Normal channel mode
// * no parity
// * No parity
let parity_mode = regs::ParityMode::None;
self.regs.mode.write(
regs::Mode::zeroed()
@ -66,12 +67,7 @@ impl Uart {
self.disable_rx();
self.disable_tx();
// 9,600 baud
self.regs.baud_rate_gen.write(regs::BaudRateGen::zeroed().cd(651));
self.regs.baud_rate_divider.write(regs::BaudRateDiv::zeroed().bdiv(7));
// // 115,200 baud
// self.regs.baud_rate_gen.write(regs::BaudRateGen::zeroed().cd(62));
// self.regs.baud_rate_divider.write(regs::BaudRateDiv::zeroed().bdiv(6));
baud_rate_gen::configure(&self.regs, 50_000_000, 9_600);
// Enable controller
self.reset_rx();