//! Serial interface loopback test
//!
//! You have to short the TX and RX pins to make this program work
#![deny(unsafe_code)]
#![no_main]
#![no_std]
use panic_halt as _;
use cortex_m::asm;
use nb::block;
use stm32f1xx_hal::{
prelude::*,
pac,
serial::Serial,
};
use cortex_m_rt::entry;
#[entry]
fn main() -> ! {
// Get access to the device specific peripherals from the peripheral access crate
let p = pac::Peripherals::take().unwrap();
// Take ownership over the raw flash and rcc devices and convert them into the corresponding
// HAL structs
let mut flash = p.FLASH.constrain();
let mut rcc = p.RCC.constrain();
// Freeze the configuration of all the clocks in the system and store the frozen frequencies in
// `clocks`
let clocks = rcc.cfgr.freeze(&mut flash.acr);
// Prepare the alternate function I/O registers
let mut afio = p.AFIO.constrain(&mut rcc.apb2);
// Prepare the GPIOB peripheral
let mut gpiob = p.GPIOB.split(&mut rcc.apb2);
// USART1
// let tx = gpioa.pa9.into_alternate_push_pull(&mut gpioa.crh);
// let rx = gpioa.pa10;
// USART1
// let tx = gpiob.pb6.into_alternate_push_pull(&mut gpiob.crl);
// let rx = gpiob.pb7;
// USART2
// let tx = gpioa.pa2.into_alternate_push_pull(&mut gpioa.crl);
// let rx = gpioa.pa3;
// USART3
// Configure pb10 as a push_pull output, this will be the tx pin
let tx = gpiob.pb10.into_alternate_push_pull(&mut gpiob.crh);
// Take ownership over pb11
let rx = gpiob.pb11;
// Set up the usart device. Taks ownership over the USART register and tx/rx pins. The rest of
// the registers are used to enable and configure the device.
let serial = Serial::usart3(
p.USART3,
(tx, rx),
&mut afio.mapr,
9_600.bps(),
clocks,
&mut rcc.apb1,
);
// Split the serial struct into a receiving and a transmitting part
let (mut tx, mut rx) = serial.split();
let sent = b'X';
// Write `X` and wait until the write is successful
block!(tx.write(sent)).ok();
// Read the byte that was just sent. Blocks until the read is complete
let received = block!(rx.read()).unwrap();
// Since we have connected tx and rx, the byte we sent should be the one we received
assert_eq!(received, sent);
// Trigger a breakpoint to allow us to inspect the values
asm::bkpt();
loop {}
}