SPI hotfix

examples/spi-example.rs

@@ -8,7 +8,6 @@
 use hal::{
     delay::DelayFromCountDownTimer,
     gpio::{AF5, PA5, PA6, PA7},
-    hal_02::spi::FullDuplex,
     prelude::*,
     pwr::PwrExt,
     rcc::Config,
@@ -49,17 +48,20 @@ fn main() -> ! {
 
     // "Hello world!"
     let message = b"Hello world!";
-    let mut received_byte: u8;
+    let mut received_msg = [0u8; 12];
 
     loop {
-        for &byte in message {
-            cs.set_low();
-            spi.send(byte).unwrap();
-            received_byte = nb::block!(FullDuplex::read(&mut spi)).unwrap();
-            cs.set_high();
+        cs.set_low();
+        // write only, nothing is received
+        spi.write(message).unwrap();
+        cs.set_high();
+
+        cs.set_low();
+        // transmit and receive at the same time
+        spi.transfer(&mut received_msg, message).unwrap();
+        info!("{received_msg:?}");
+        cs.set_high();
 
-            info!("{}", received_byte as char);
-        }
         delay_tim2.delay_ms(1000);
     }
 }

src/spi.rs

@@ -186,20 +186,24 @@ impl<SPI: Instance, PINS> Spi<SPI, PINS> {
     fn read_unchecked<W: FrameSize>(&mut self) -> W {
         // NOTE(read_volatile) read only 1 byte (the svd2rust API only allows
         // reading a half-word)
-        unsafe { ptr::read_volatile(&self.spi.dr() as *const _ as *const W) }
+        unsafe { ptr::read_volatile(self.spi.dr().as_ptr() as *const W) }
     }
     #[inline]
     fn write_unchecked<W: FrameSize>(&mut self, word: W) {
         // NOTE(write_volatile) see note above
         let dr = self.spi.dr().as_ptr() as *mut W;
         unsafe { ptr::write_volatile(dr, word) };
     }
+    /// disables rx
     #[inline]
     pub fn set_tx_only(&mut self) {
+        // very counter-intuitively, setting spi bidi mode on disables rx while transmitting
+        // it's made for half-duplex spi, which they called bidirectional in the manual
         self.spi
             .cr1()
             .modify(|_, w| w.bidimode().bidirectional().bidioe().output_enabled());
     }
+    /// re-enables rx if it was disabled
     #[inline]
     pub fn set_bidi(&mut self) {
         self.spi
@@ -314,6 +318,7 @@ impl<SPI: Instance, PINS: Pins<SPI>> embedded_hal::spi::SpiBus<u8> for Spi<SPI,
         self.set_bidi();
 
         let half_len = len / 2;
+        // leftover write/read operation because bytes are not a multiple of 2
         let pair_left = len % 2;
 
         // prefill write fifo so that the clock doen't stop while fetch the read byte