S/PDIF receiver library for Raspberry Pi Pico series

Overview

• S/PDIF receiver with sampling frequency detection by PIO function
• Supported format:
  • Channels: 2 (Stereo)
  • Bit resolution: 16bit and 24bit
• Supported sampling frequencies:
  • 44.1 KHz, 48.0 KHz, 88.2 KHz, 96.0 KHz, 176.4 KHz and 192.0 KHz for Raspberry Pi Pico (rp2040)
  • 44.1 KHz, 48.0 KHz, 88.2 KHz and 96.0 KHz for Raspberry Pi Pico 2 (rp2350)

Supported Board and Peripheral Devices

• Raspberry Pi Pico (rp2040)
• Raspberry Pi Pico 2 (rp2350)
• S/PDIF Coaxial or TOSLINK Rx module (DLR1160 or equivalent)

Pin Assignment & Connection

S/PDIF Rx

Pico Pin #	GPIO	Function	Connection
20	GP15	DATA	from S/PDIF data

Notes:

• 74HC04 should be genuine device, otherwise (counterfeit device) it could not work at higher sampling frequencies.
• if TOSLINK only, direct connection from module output to GP15 will work as well.

How to build

• See "Getting started with Raspberry Pi Pico"
• Put "pico-sdk", "pico-examples" and "pico-extras" on the same level with this project folder.
• Set environmental variables for PICO_SDK_PATH, PICO_EXTRAS_PATH and PICO_EXAMPLES_PATH
• Confirmed with Pico SDK 2.1.1

> git clone -b 2.1.1 https://github.com/raspberrypi/pico-sdk.git
> cd pico-sdk
> git submodule update -i
> cd ..
> git clone -b sdk-2.1.1 https://github.com/raspberrypi/pico-examples.git
>
> git clone -b sdk-2.1.1 https://github.com/raspberrypi/pico-extras.git
> 
> git clone -b main https://github.com/elehobica/pico_spdif_rx.git

Windows

• Build is confirmed with Developer Command Prompt for VS 2022 and Visual Studio Code on Windows environment
• Confirmed with cmake-3.27.2-windows-x86_64 and gcc-arm-none-eabi-10.3-2021.10-win32
• Lanuch "Developer Command Prompt for VS 2022"

> cd pico_spdif_rx\samples\xxxxx  # sample project directory
> mkdir build && cd build
> cmake -G "NMake Makefiles" ..  ; (for Raspberry Pi Pico 1 series)
> cmake -G "NMake Makefiles" -DPICO_PLATFORM=rp2350 -DPICO_BOARD=pico2 ..  ; (for Raspberry Pi Pico 2)
> nmake

• Put "*.uf2" on RPI-RP2 or RP2350 drive

Linux

• Build is confirmed with pico-sdk-dev-docker:sdk-2.1.1-1.0.0
• Confirmed with cmake-3.22.1 and arm-none-eabi-gcc (15:10.3-2021.07-4) 10.3.1

$ cd pico_spdif_rx/samples/xxxxx  # sample project directory
$ mkdir build && cd build
$ cmake ..  # (for Raspberry Pi Pico 1 series)
$ cmake -DPICO_PLATFORM=rp2350 -DPICO_BOARD=pico2 ..  # (for Raspberry Pi Pico 2)
$ make -j4

• Download "*.uf2" on RPI-RP2 or RP2350 drive

Decode output format

• 32bit output for each S/PDIF sub frame including header, audio data, AUX, VUCP
• see comments in spdif_rx.pio for further detail

Sample projects

detect_samp_freq

• display sampling frequency, C bits of S/PDIF frame and number of parity errors while decoding

spdif_to_i2s_32b

• convert S/PDIF input to I2S 32bit output

Application Examples

• pico_spdif_recorder
• pico_spdif_dac_hpamp