//! # ADC FIFO DMA Example
//!
//! This application demonstrates how to read ADC samples in free-running mode,
//! and reading them from the FIFO by using a DMA transfer.
//!
//! It may need to be adapted to your particular board layout and/or pin assignment.
//!
//! See the `Cargo.toml` file for Copyright and license details.
#![no_std]
#![no_main]
// Ensure we halt the program on panic (if we don't mention this crate it won't
// be linked)
use panic_halt as _;
// Alias for our HAL crate
use rp2040_hal as hal;
// Some traits we need
use core::fmt::Write;
use cortex_m::singleton;
use fugit::RateExtU32;
use hal::dma::{single_buffer, DMAExt};
use rp2040_hal::Clock;
// UART related types
use hal::uart::{DataBits, StopBits, UartConfig};
// A shorter alias for the Peripheral Access Crate, which provides low-level
// register access
use hal::pac;
/// The linker will place this boot block at the start of our program image. We
/// need this to help the ROM bootloader get our code up and running.
/// Note: This boot block is not necessary when using a rp-hal based BSP
/// as the BSPs already perform this step.
#[link_section = ".boot2"]
#[used]
pub static BOOT2: [u8; 256] = rp2040_boot2::BOOT_LOADER_GENERIC_03H;
/// External high-speed crystal on the Raspberry Pi Pico board is 12 MHz. Adjust
/// if your board has a different frequency
const XTAL_FREQ_HZ: u32 = 12_000_000u32;
/// Entry point to our bare-metal application.
///
/// The `#[rp2040_hal::entry]` macro ensures the Cortex-M start-up code calls this function
/// as soon as all global variables and the spinlock are initialised.
///
/// The function configures the RP2040 peripherals, then prints the temperature
/// in an infinite loop.
#[rp2040_hal::entry]
fn main() -> ! {
// Grab our singleton objects
let mut pac = pac::Peripherals::take().unwrap();
let core = pac::CorePeripherals::take().unwrap();
// Set up the watchdog driver - needed by the clock setup code
let mut watchdog = hal::Watchdog::new(pac.WATCHDOG);
// Configure the clocks
let clocks = hal::clocks::init_clocks_and_plls(
XTAL_FREQ_HZ,
pac.XOSC,
pac.CLOCKS,
pac.PLL_SYS,
pac.PLL_USB,
&mut pac.RESETS,
&mut watchdog,
)
.unwrap();
// The delay object lets us wait for specified amounts of time (in
// milliseconds)
let mut delay = cortex_m::delay::Delay::new(core.SYST, clocks.system_clock.freq().to_Hz());
// The single-cycle I/O block controls our GPIO pins
let sio = hal::Sio::new(pac.SIO);
// Set the pins to their default state
let pins = hal::gpio::Pins::new(
pac.IO_BANK0,
pac.PADS_BANK0,
sio.gpio_bank0,
&mut pac.RESETS,
);
// UART TX (characters sent from pico) on pin 1 (GPIO0) and RX (on pin 2 (GPIO1)
let uart_pins = (
pins.gpio0.into_function::<hal::gpio::FunctionUart>(),
pins.gpio1.into_function::<hal::gpio::FunctionUart>(),
);
// Create a UART driver
let mut uart = hal::uart::UartPeripheral::new(pac.UART0, uart_pins, &mut pac.RESETS)
.enable(
UartConfig::new(115200.Hz(), DataBits::Eight, None, StopBits::One),
clocks.peripheral_clock.freq(),
)
.unwrap();
// Write to the UART
uart.write_full_blocking(b"ADC FIFO DMA example\r\n");
// Initialize DMA
let dma = pac.DMA.split(&mut pac.RESETS);
// Enable ADC
let mut adc = hal::Adc::new(pac.ADC, &mut pac.RESETS);
// Enable the temperature sense channel
let mut temperature_sensor = adc.take_temp_sensor().unwrap();
// Configure GPIO26 as an ADC input
let adc_pin_0 = hal::adc::AdcPin::new(pins.gpio26.into_floating_input()).unwrap();
// we'll capture 1000 samples in total (500 per channel)
// NOTE: when calling `shift_8bit` below, the type here must be changed from `u16` to `u8`
let buf_for_samples = singleton!(: [u16; 1000] = [0; 1000]).unwrap();
// Configure free-running mode:
let mut adc_fifo = adc
.build_fifo()
// Set clock divider to target a sample rate of 1000 samples per second (1ksps).
// The value was calculated by `(48MHz / 1ksps) - 1 = 47999.0`.
// Please check the `clock_divider` method documentation for details.
.clock_divider(47999, 0)
// sample the temperature sensor first
.set_channel(&mut temperature_sensor)
// then alternate between GPIO26 and the temperature sensor
.round_robin((&adc_pin_0, &temperature_sensor))
// Uncomment this line to produce 8-bit samples, instead of 12 bit (lower bits are discarded)
//.shift_8bit()
// Enable DMA transfers for the FIFO
.enable_dma()
// Create the FIFO, but don't start it just yet
.start_paused();
// Start a DMA transfer (must happen before resuming the ADC FIFO)
let dma_transfer =
single_buffer::Config::new(dma.ch0, adc_fifo.dma_read_target(), buf_for_samples).start();
// Resume the FIFO to start capturing
adc_fifo.resume();
// initialize a timer, to measure the total sampling time (printed below)
let timer = hal::Timer::new(pac.TIMER, &mut pac.RESETS, &clocks);
// NOTE: in a real-world program, instead of calling `wait` now, you would probably:
// 1. Enable one of the DMA interrupts for the channel (e.g. `dma.ch0.enable_irq0()`)
// 2. Set up a handler for the respective `DMA_IRQ_*` interrupt
// 3. Call `wait` only within that interrupt, which will be fired once the transfer is complete.
// the DMA unit takes care of shuffling data from the FIFO into the buffer.
// We just sit here and wait... 😴
let (_ch, _adc_read_target, buf_for_samples) = dma_transfer.wait();
// ^^^ the three results here (channel, adc::DmaReadTarget, write target) can be reused
// right away to start another transfer.
let time_taken = timer.get_counter();
uart.write_full_blocking(b"Done sampling, printing results:\r\n");
// Stop free-running mode (the returned `adc` can be reused for future captures)
let _adc = adc_fifo.stop();
// Print the measured values
for i in 0..500 {
writeln!(
uart,
"Temp:\t{}\tPin\t{}\r",
buf_for_samples[i * 2],
buf_for_samples[i * 2 + 1]
)
.unwrap();
}
writeln!(uart, "Sampling took: {}\r", time_taken).unwrap();
loop {
delay.delay_ms(1000);
}
}
// End of file