https://github.com/tinygo-org/pio
Programmable I/O API for RP2040.
https://github.com/tinygo-org/pio
Last synced: 4 months ago
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Programmable I/O API for RP2040.
- Host: GitHub
- URL: https://github.com/tinygo-org/pio
- Owner: tinygo-org
- License: bsd-3-clause
- Created: 2023-10-28T02:41:20.000Z (over 1 year ago)
- Default Branch: main
- Last Pushed: 2024-04-15T00:58:04.000Z (about 1 year ago)
- Last Synced: 2024-05-01T16:22:44.519Z (about 1 year ago)
- Language: Go
- Homepage:
- Size: 157 KB
- Stars: 17
- Watchers: 6
- Forks: 0
- Open Issues: 4
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
- awesome-tinygo - pio - Programmable I/O API for RP2040/RP2350 using TinyGo (Embedded Systems / General use)
README
# pio
[](https://github.com/tinygo-org/pio/actions/workflows/build.yml)
Provides clean API to interact with RP2040/RP2350 on-board Programable Input/Output (PIO) block.
See chapter 3 of the [RP2040 datasheet](https://datasheets.raspberrypi.com/rp2040/rp2040-datasheet.pdf#page=310) for more information.
### piolib
This module contains the [piolib](./rp2-pio/piolib) package which contains importable drivers for use with a PIO such as:
- SPI driver
- 8-pin send-only parallel bus
- WS2812 (Neopixel) driver
- A pulse-constrained square wave generator (Pulsar)
## Introduction to PIO
The PIO is a versatile hardware interface. It can support a variety of IO standards,
including:
- 8080 and 6800 parallel bus
- I2C
- 3-pin I2S
- SDIO
- SPI, DSPI, QSPI
- UART
- DPI or VGA (via resistor DAC)
PIO is programmable in the same sense as a processor and has a total of nine instructions: JMP, WAIT, IN, OUT, PUSH, PULL, MOV, IRQ, and SET. These are programmed in PIO assembly format describing a PIO program, where each command corresponds to one instruction in the output binary. Below is an example program in PIO assembly:
```pio
.program squarewave
again:
set pins, 1 [1] ; Drive pin high and then delay for one cycle
set pins, 0 ; Drive pin low
jmp again ; Set PC to label `again`
```
### How to install pioasm
To develop new code using PIO with this package, you must build and install the `pioasm` tool. It can be be built from the pico-sdk:
```shell
git clone [email protected]:raspberrypi/pico-sdk.git
cd pico-sdk/tools/pioasm
cmake .
make
sudo make install
```
### How to develop a PIO program
To develop a PIO program you first start out with the .pio file. Let's look at the Pulsar example first.
1. [`pulsar.pio`](./rp2-pio/piolib/pulsar.pio): specifies a binary PIO program that can be loaded to the PIO program memory.
2. [`all_generate.go`](./rp2-pio/piolib/all_generate.go): holds the code generation command on the line with `//go:generate pioasm -o go pulsar.pio pulsar_pio.go` which by itself generates the raw binary code that can be loaded onto the PIO along with helper code to load it correctly inside `pulsar_pio.go`.
3. [`pulsar_pio.go`](./rp2-pio/piolib/pulsar_pio.go): contains the generated code by the `pioasm` tool.
4. [`pulsar.go`](./rp2-pio/piolib/pulsar.go): contains the User facing code that allows using the PIO as intended by the author.
### Regenerating piolib
```shell
go generate ./...
```
### Other notes
Keep in mind PIO programs are very finnicky, especially differentiating between SetOutPins and SetSetPins. The difference is subtle but it can be the difference between spending days debugging a silly conceptual mistake. Have fun!