README.md

Raspberry Pi Pico SDK Examples

Getting started

See Getting Started with the Raspberry Pi Pico and the README in the pico-sdk for information on getting up and running.

First Examples

App	Description	Link to prebuilt UF2
hello_serial	The obligatory Hello World program for Pico (Output over serial version)
hello_usb	The obligatory Hello World program for Pico (Output over USB version)	https://rptl.io/pico-hello-usb
blink	Blink an LED on and off.	https://rptl.io/pico-blink

ADC

App	Description
hello_adc	Display the voltage from an ADC input.
joystick_display	Display a Joystick X/Y input based on two ADC inputs.
adc_console	An interactive shell for playing with the ADC. Includes example of free-running capture mode.
microphone_adc	Read analog values from a microphone and plot the measured sound amplitude.

Clocks

App	Description
hello_48MHz	Change the system clock frequency to 48 MHz while running.
hello_gpout	Use the general purpose clock outputs (GPOUT) to drive divisions of internal clocks onto GPIO outputs.
hello_resus	Enable the clock resuscitate feature, "accidentally" stop the system clock, and show how we recover.

CMake

App	Description
build_variants	Builds two version of the same app with different configurations

DMA

App	Description
hello_dma	Use the DMA to copy data in memory.
control_blocks	Build a control block list, to program a longer sequence of DMA transfers to the UART.
channel_irq	Use an IRQ handler to reconfigure a DMA channel, in order to continuously drive data through a PIO state machine.

Flash

App	Description
cache_perfctr	Read and clear the cache performance counters. Show how they are affected by different types of flash reads.
nuke	Obliterate the contents of flash. An example of a NO_FLASH binary (UF2 loaded directly into SRAM and runs in-place there). A useful utility to drag and drop onto your Pico if the need arises.
program	Erase a flash sector, program one flash page, and read back the data.
xip_stream	Stream data using the XIP stream hardware, which allows data to be DMA'd in the background whilst executing code from flash.
ssi_dma	DMA directly from the flash interface (continuous SCK clocking) for maximum bulk read performance.

GPIO

App	Description
hello_7segment	Use the GPIOs to drive a seven segment LED display.
hello_gpio_irq	Register an interrupt handler to run when a GPIO is toggled.
dht_sensor	Use GPIO to bitbang the serial protocol for a DHT temperature/humidity sensor.

See also: blink, blinking an LED attached to a GPIO.

HW divider

App	Description
hello_divider	Show how to directly access the hardware integer dividers, in case AEABI injection is disabled.

I2C

App	Description
bus_scan	Scan the I2C bus for devices and display results.
bmp280_i2c	Read and convert temperature and pressure data from a BMP280 sensor, attached to an I2C bus.
lcd_1602_i2c	Display some text on a generic 16x2 character LCD display, via I2C.
lis3dh_i2c	Read acceleration and temperature value from a LIS3DH sensor via I2C
mcp9808_i2c	Read temperature, set limits and raise alerts when limits are surpassed.
mma8451_i2c	Read acceleration from a MMA8451 accelerometer and set range and precision for the data.
mpl3115a2_i2c	Interface with an MPL3115A2 altimeter, exploring interrupts and advanced board features, via I2C.
mpu6050_i2c	Read acceleration and angular rate values from a MPU6050 accelerometer/gyro, attached to an I2C bus.
oled_i2c	Convert and display a bitmap on a 128x32 SSD1306-driven OLED display
pa1010d_i2c	Read GPS location data, parse and display data via I2C.
pcf8523_i2c	Read time and date values from a real time clock. Set current time and alarms on it.

Interpolator

App	Description
hello_interp	A bundle of small examples, showing how to access the core-local interpolator hardware, and use most of its features.

Multicore

App	Description
hello_multicore	Launch a function on the second core, printf some messages on each core, and pass data back and forth through the mailbox FIFOs.
multicore_fifo_irqs	On each core, register and interrupt handler for the mailbox FIFOs. Show how the interrupt fires when that core receives a message.
multicore_runner	Set up the second core to accept, and run, any function pointer pushed into its mailbox FIFO. Push in a few pieces of code and get answers back.

Pico Board

App	Description
blinky	Blink "hello, world" in Morse code on Pico's LED
button	Use Pico's BOOTSEL button as a regular button input, by temporarily suspending flash access.

PIO

App	Description
hello_pio	Absolutely minimal example showing how to control an LED by pushing values into a PIO FIFO.
apa102	Rainbow pattern on on a string of APA102 addressable RGB LEDs.
differential_manchester	Send and receive differential Manchester-encoded serial (BMC).
hub75	Display an image on a 128x64 HUB75 RGB LED matrix.
i2c	Scan an I2C bus.
ir_nec	Sending and receiving IR (infra-red) codes using the PIO.
logic_analyser	Use PIO and DMA to capture a logic trace of some GPIOs, whilst a PWM unit is driving them.
manchester_encoding	Send and receive Manchester-encoded serial.
pio_blink	Set up some PIO state machines to blink LEDs at different frequencies, according to delay counts pushed into their FIFOs.
pwm	Pulse width modulation on PIO. Use it to gradually fade the brightness of an LED.
spi	Use PIO to erase, program and read an external SPI flash chip. A second example runs a loopback test with all four CPHA/CPOL combinations.
squarewave	Drive a fast square wave onto a GPIO. This example accesses low-level PIO registers directly, instead of using the SDK functions.
st7789_lcd	Set up PIO for 62.5 Mbps serial output, and use this to display a spinning image on a ST7789 serial LCD.
quadrature_encoder	A quadrature encoder using PIO to maintain counts independent of the CPU.
uart_rx	Implement the receive component of a UART serial port. Attach it to the spare Arm UART to see it receive characters.
uart_tx	Implement the transmit component of a UART serial port, and print hello world.
ws2812	Examples of driving WS2812 addressable RGB LEDs.
addition	Add two integers together using PIO. Only around 8 billion times slower than Cortex-M0+.

PWM

App	Description
hello_pwm	Minimal example of driving PWM output on GPIOs.
led_fade	Fade an LED between low and high brightness. An interrupt handler updates the PWM slice's output level each time the counter wraps.
measure_duty_cycle	Drives a PWM output at a range of duty cycles, and uses another PWM slice in input mode to measure the duty cycle.

Reset

App	Description
hello_reset	Perform a hard reset on some peripherals, then bring them back up.

RTC

App	Description
hello_rtc	Set a date/time on the RTC, then repeatedly print the current time, 10 times per second, to show it updating.
rtc_alarm	Set an alarm on the RTC to trigger an interrupt at a date/time 5 seconds into the future.
rtc_alarm_repeat	Trigger an RTC interrupt once per minute.

SPI

App	Description
bme280_spi	Attach a BME280 temperature/humidity/pressure sensor via SPI.
mpu9250_spi	Attach a MPU9250 accelerometer/gyoscope via SPI.
spi_dma	Use DMA to transfer data both to and from the SPI simultaneously. The SPI is configured for loopback.
spi_flash	Erase, program and read a serial flash device attached to one of the SPI controllers.

System

App	Description
hello_double_tap	An LED blink with the pico_bootsel_via_double_reset library linked. This enters the USB bootloader when it detects the system being reset twice in quick succession, which is useful for boards with a reset button but no BOOTSEL button.
narrow_io_write	Demonstrate the effects of 8-bit and 16-bit writes on a 32-bit IO register.
unique_board_id	Read the 64 bit unique ID from external flash, which serves as a unique identifier for the board.

Timer

App	Description
hello_timer	Set callbacks on the system timer, which repeat at regular intervals. Cancel the timer when we're done.
periodic_sampler	Sample GPIOs in a timer callback, and push the samples into a concurrency-safe queue. Pop data from the queue in code running in the foreground.
timer_lowlevel	Example of direct access to the timer hardware. Not generally recommended, as the SDK may use the timer for IO timeouts.

UART

App	Description
hello_uart	Print some text from one of the UART serial ports, without going through stdio.
lcd_uart	Display text and symbols on a 16x02 RGB LCD display via UART
uart_advanced	Use some other UART features like RX interrupts, hardware control flow, and data formats other than 8n1.

USB Device

TinyUSB Examples

Most of the USB device examples come directly from the TinyUSB device examples directory here. Those that are supported on RP2040 devices are automatically included as part of the pico-examples build as targets named tinyusb_dev_<example_name>, e.g. https://github.com/hathach/tinyusb/tree/master/examples/device/hid_composite is built as tinyusb_dev_hid_composite.

At the time of writing, these examples are available:

• tinyusb_dev_audio_4_channel_mic
• tinyusb_dev_audio_test
• tinyusb_dev_board_test
• tinyusb_dev_cdc_dual_ports
• tinyusb_dev_cdc_msc
• tinyusb_dev_dfu
• tinyusb_dev_dfu_runtime
• tinyusb_dev_dynamic_configuration
• tinyusb_dev_hid_composite
• tinyusb_dev_hid_generic_inout
• tinyusb_dev_hid_multiple_interface
• tinyusb_dev_midi_test
• tinyusb_dev_msc_dual_lun
• tinyusb_dev_net_lwip_webserver
• tinyusb_dev_uac2_headset
• tinyusb_dev_usbtmc
• tinyusb_dev_video_capture
• tinyusb_dev_webusb_serial

Whilst these examples ably demonstrate how to use TinyUSB in device mode, their CMakeLists.txt is set up in a way tailored to how TinyUSB builds their examples within their source tree.

For a better example of how to configure CMakeLists.txt for using TinyUSB in device mode with the Raspberry Pi SDK see below:

SDK build example

App	Description
dev_hid_composite	A copy of the TinyUSB device example with the same name, but with a CMakeLists.txt which demonstrates how to add a dependency on the TinyUSB device libraries with the Raspberry Pi Pico SDK

Low Level example

App	Description
dev_lowlevel	A USB Bulk loopback implemented with direct access to the USB hardware (no TinyUSB)

USB Host

All the USB host examples come directly from the TinyUSB host examples directory here. Those that are supported on RP2040 devices are automatically included as part of the pico-examples build as targets named tinyusb_host_<example_name>, e.g. https://github.com/hathach/tinyusb/tree/master/examples/host/cdc_msc_hid is built as tinyusb_host_cdc_msc_hid.

At the time of writing, there is only one host example available:

• tinyusb_host_cdc_msc_hid

Watchdog

App	Description
hello_watchdog	Set the watchdog timer, and let it expire. Detect the reboot, and halt.