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- //! Serial interface loopback test
- //!
- //! You have to short the TX and RX pins to make this program work
- #![deny(unsafe_code)]
- #![deny(warnings)]
- #![no_main]
- #![no_std]
- extern crate panic_halt;
- 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 {}
- }
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