SPI DMA RX/TX example

Author: korken89

Cargo.toml

@@ -120,6 +120,10 @@ required-features = ["rt"]
 name = "rtic_frame_serial_dma"
 required-features = ["rt", "stm32l4x2"]
 
+[[example]]
+name = "spi_dma_rxtx"
+required-features = ["rt", "stm32l4x2"]
+
 [[example]]
 name = "serial_echo_rtic"
 required-features = ["rt", "stm32l4x3"]

examples/spi_dma_rxtx.rs

@@ -0,0 +1,103 @@
+//! Test the SPI in RX/TX (transfer) DMA mode
+#![deny(unsafe_code)]
+#![no_main]
+#![no_std]
+
+use panic_rtt_target as _;
+use rtt_target::rprintln;
+use stm32l4xx_hal::{
+    dma::TransferDma,
+    gpio::{Speed, State as PinState},
+    hal::spi::{Mode, Phase, Polarity},
+    prelude::*,
+    rcc::{ClockSecuritySystem, CrystalBypass, MsiFreq},
+    spi::Spi,
+};
+
+#[rtic::app(device = stm32l4xx_hal::pac, peripherals = true)]
+const APP: () = {
+    #[init]
+    fn init(cx: init::Context) {
+        static mut DMA_BUF: [u8; 5] = [0xf0, 0xaa, 0x00, 0xff, 0x0f];
+
+        rtt_target::rtt_init_print!();
+        rprintln!("Initializing... ");
+
+        let dp = cx.device;
+
+        let mut flash = dp.FLASH.constrain();
+        let mut rcc = dp.RCC.constrain();
+        let mut pwr = dp.PWR.constrain(&mut rcc.apb1r1);
+        let mut gpiob = dp.GPIOB.split(&mut rcc.ahb2);
+        let dma1_channels = dp.DMA1.split(&mut rcc.ahb1);
+
+        //
+        // Initialize the clocks to 80 MHz
+        //
+        rprintln!("  - Clock init");
+        let clocks = rcc
+            .cfgr
+            .lse(CrystalBypass::Enable, ClockSecuritySystem::Disable)
+            .hsi48(true) // For RNG
+            .msi(MsiFreq::RANGE4M)
+            .sysclk(80.mhz())
+            .freeze(&mut flash.acr, &mut pwr);
+
+        //
+        // Initialize the SPI
+        //
+        let sck = gpiob
+            .pb3
+            .into_af5(&mut gpiob.moder, &mut gpiob.afrl)
+            .set_speed(Speed::High);
+        let miso = gpiob
+            .pb4
+            .into_af5(&mut gpiob.moder, &mut gpiob.afrl)
+            .set_speed(Speed::High);
+        let mosi = gpiob
+            .pb5
+            .into_af5(&mut gpiob.moder, &mut gpiob.afrl)
+            .set_speed(Speed::High);
+        let mut dummy_cs = gpiob.pb6.into_push_pull_output_with_state(
+            &mut gpiob.moder,
+            &mut gpiob.otyper,
+            PinState::High,
+        );
+        let spi = Spi::spi1(
+            dp.SPI1,
+            (sck, miso, mosi),
+            Mode {
+                phase: Phase::CaptureOnFirstTransition,
+                polarity: Polarity::IdleLow,
+            },
+            100.khz(),
+            clocks,
+            &mut rcc.apb2,
+        );
+
+        // Create DMA SPI
+        let dma_spi = spi.with_rxtx_dma(dma1_channels.2, dma1_channels.3);
+
+        // Check the buffer before using it
+        rprintln!("buf pre: 0x{:x?}", &DMA_BUF);
+
+        // Perform transfer and wait for it to finish (blocking), this can also be done using
+        // interrupts on the desired DMA channel
+        dummy_cs.set_low().ok();
+        let transfer = dma_spi.transfer(DMA_BUF);
+        let (buf, _dma_spi) = transfer.wait();
+        dummy_cs.set_high().ok();
+
+        // Inspect the extracted buffer, if the MISO is connected to VCC or GND it will be all 0 or
+        // 1.
+        rprintln!("buf post: 0x{:x?}", &buf);
+    }
+
+    // Idle function so RTT keeps working
+    #[idle]
+    fn idle(_cx: idle::Context) -> ! {
+        loop {
+            continue;
+        }
+    }
+};