spi problem

[eighteen-k-gold-malow]

For the W25Q64 (Flash) hardware, if the cs register is not set before transmission, sometimes the data can be read, and sometimes the data cannot be read.

Output

[255, 239, 64, 23]

#![no_std]
#![no_main]
use cortex_m_rt::entry;
use cortex_m::Peripherals;

use cortex_m_semihosting::debug::exit;
use cortex_m_semihosting::hprintln;
// pick a panicking behavior
use panic_halt as _; 
// you can put a breakpoint on `rust_begin_unwind` to catch panics
// use panic_abort as _; // requires nightly
// use panic_itm as _; // logs messages over ITM; requires ITM support
// use panic_semihosting as _; // logs messages to the host stderr; requires a debugger
use stm32f1xx_hal::pac as pac;
use stm32f1xx_hal::prelude::*;
use stm32f1xx_hal::spi::Mode;
use stm32f1xx_hal::spi::Phase;
use stm32f1xx_hal::spi::Spi;
use stm32f1xx_hal::spi::Polarity;


#[entry]
fn main() -> ! {
    let cp = Peripherals::take().unwrap();
    let dp = pac::Peripherals::take().unwrap();
    let rcc = dp.RCC.constrain();
    let mut flash = dp.FLASH.constrain();
    let clocks = rcc.cfgr.freeze(&mut flash.acr);
    let mut afio = dp.AFIO.constrain();

    let mut gpioa = dp.GPIOA.split();


    let pins = (
        gpioa.pa5.into_alternate_push_pull(&mut gpioa.crl), 
        gpioa.pa6.into_pull_up_input(&mut gpioa.crl),
        gpioa.pa7.into_alternate_push_pull(&mut gpioa.crl)
    );

    let mut spi = Spi::spi1(dp.SPI1, pins, &mut afio.mapr, Mode {
        polarity: Polarity::IdleLow,
        phase: Phase::CaptureOnFirstTransition,
    }, 8.MHz(), clocks);
    

    // initialze spi
    let mut cs = gpioa.pa4.into_push_pull_output(&mut gpioa.crl);
    cs.set_high();  


    // start spi
    cs.set_low(); 


    let mut buf = [0x9f, 0xff, 0xff, 0xff];
    spi.transfer(&mut buf).unwrap();

    // stop spi
    cs.set_high();  

    hprintln!("{:?}", buf);


    exit(Ok(()));
    loop {
        
    }
  
}
                                                        

[burrbull]

You should use SpiDevice. See https://docs.rs/embedded-hal-bus/latest/embedded_hal_bus/spi/struct.ExclusiveDevice.html or another wrappers.