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// # Example of blocking TSC (Touch Sensing Controller) that lights an LED when touch is detected
//
// This example demonstrates how to use the Touch Sensing Controller (TSC) in blocking mode on an STM32L4R5ZI-P board.
//
// ## This example demonstrates:
//
// 1. Configuring a single TSC channel pin
// 2. Using the blocking TSC interface with polling
// 3. Waiting for acquisition completion using `poll_for_acquisition`
// 4. Reading touch values and controlling an LED based on the results
//
// ## Suggested physical setup on STM32L4R5ZI-P board:
//
// - Connect a 1000pF capacitor between pin PB4 (D25) and GND. This is your sampling capacitor.
// - Connect one end of a 1K resistor to pin PB5 (D21) and leave the other end loose.
// The loose end will act as the touch sensor which will register your touch.
//
// ## Pin Configuration:
//
// The example uses two pins from Group 2 of the TSC:
// - PB4 (D25) as the sampling capacitor, TSC group 2 IO1
// - PB5 (D21) as the channel pin, TSC group 2 IO2
//
// ## Program Behavior:
//
// The program continuously reads the touch sensor value:
// - It starts acquisition, waits for completion using `poll_for_acquisition`, and reads the value.
// - The LED (connected to PB14) is turned on when touch is detected (sensor value < SENSOR_THRESHOLD).
// - Touch values are logged to the console.
//
// ## Troubleshooting:
//
// - If touch is not detected, try adjusting the SENSOR_THRESHOLD value (currently set to 25).
// - Experiment with different values for ct_pulse_high_length, ct_pulse_low_length,
// pulse_generator_prescaler, max_count_value, and discharge_delay to optimize sensitivity.
// - Be aware that for some boards, there might be overlapping concerns between some pins,
// such as UART connections for the programmer. No errors or warnings will be emitted if you
// try to use such a pin for TSC, but you may get strange sensor readings.
//
// Note: Configuration values and sampling capacitor value have been determined experimentally.
// Optimal values may vary based on your specific hardware setup. Refer to the official
// STM32L4R5ZI-P datasheet and user manuals for more information on pin configurations and TSC functionality.
#![no_std]
#![no_main]
use defmt::*;
use embassy_stm32::gpio::{Level, Output, Speed};
use embassy_stm32::tsc::{self, *};
use embassy_stm32::{mode, peripherals};
use embassy_time::Timer;
use {defmt_rtt as _, panic_probe as _};
const SENSOR_THRESHOLD: u16 = 25; // Adjust this value based on your setup
#[embassy_executor::main]
async fn main(_spawner: embassy_executor::Spawner) {
let device_config = embassy_stm32::Config::default();
let context = embassy_stm32::init(device_config);
let tsc_conf = Config {
ct_pulse_high_length: ChargeTransferPulseCycle::_4,
ct_pulse_low_length: ChargeTransferPulseCycle::_4,
spread_spectrum: false,
spread_spectrum_deviation: SSDeviation::new(2).unwrap(),
spread_spectrum_prescaler: false,
pulse_generator_prescaler: PGPrescalerDivider::_16,
max_count_value: MaxCount::_255,
io_default_mode: false,
synchro_pin_polarity: false,
acquisition_mode: false,
max_count_interrupt: false,
};
let mut g2: PinGroupWithRoles<peripherals::TSC, G2> = PinGroupWithRoles::default();
// D25
g2.set_io1::<tsc::pin_roles::Sample>(context.PB4);
// D21
let tsc_sensor = g2.set_io2::<tsc::pin_roles::Channel>(context.PB5);
let pin_groups: PinGroups<peripherals::TSC> = PinGroups {
g2: Some(g2.pin_group),
..Default::default()
};
let mut touch_controller = tsc::Tsc::new_blocking(context.TSC, pin_groups, tsc_conf).unwrap();
// Check if TSC is ready
if touch_controller.get_state() != State::Ready {
crate::panic!("TSC not ready!");
}
info!("TSC initialized successfully");
let mut led = Output::new(context.PB14, Level::High, Speed::Low);
// smaller sample capacitor discharge faster and can be used with shorter delay.
let discharge_delay = 5; // ms
// the interval at which the loop polls for new touch sensor values
let polling_interval = 100; // ms
info!("polling for touch");
loop {
touch_controller.set_active_channels_mask(tsc_sensor.pin.into());
touch_controller.start();
touch_controller.poll_for_acquisition();
touch_controller.discharge_io(true);
Timer::after_millis(discharge_delay).await;
match read_touch_value(&mut touch_controller, tsc_sensor.pin).await {
Some(v) => {
info!("sensor value {}", v);
if v < SENSOR_THRESHOLD {
led.set_high();
} else {
led.set_low();
}
}
None => led.set_low(),
}
Timer::after_millis(polling_interval).await;
}
}
const MAX_GROUP_STATUS_READ_ATTEMPTS: usize = 10;
// attempt to read group status and delay when still ongoing
async fn read_touch_value(
touch_controller: &mut tsc::Tsc<'_, peripherals::TSC, mode::Blocking>,
sensor_pin: tsc::IOPin,
) -> Option<u16> {
for _ in 0..MAX_GROUP_STATUS_READ_ATTEMPTS {
match touch_controller.group_get_status(sensor_pin.group()) {
GroupStatus::Complete => {
return Some(touch_controller.group_get_value(sensor_pin.group()));
}
GroupStatus::Ongoing => {
// if you end up here a lot, then you prob need to increase discharge_delay
// or consider changing the code to adjust the discharge_delay dynamically
info!("Acquisition still ongoing");
Timer::after_millis(1).await;
}
}
}
None
}
|
