Open Source I2C Gpio Expander

This project provides an open-source I2C GPIO Expander, fully written in SpinalHDL, and designed for use with the OpenROAD toolchain. The expander is compatible with the SG13G2 PDK, offering a complete open-source solution from RTL to GDSII without relying on proprietary tools.

Features

SpinalHDL Implementation: The entire design is written in SpinalHDL, with no Verilog or VHDL code.
Open-Source Toolchain: The project uses only open-source tools, avoiding proprietary software.
- Design Verification: Performed using Yosys and nextpnr.
- Chip Layout: Achieved with OpenROAD.
I2C Fast Mode: Supports I2C communication at 400 kbit/s.
Configurable GPIO Width: Flexible design allows customizable GPIO widths based on requirements.
Configurable Address Width: The I2C address width can also be configured as needed.

This project is ideal for those looking to implement a customizable I2C GPIO expander with full support from open-source tools and platforms.

Layout Rendering

Rendering of the standard cells alongside some I/O cells.

A detailed view of the power/ground mesh and selected cells.

The power distribution network: Power and ground I/O cells on the left connect to the central power/ground ring, which distributes through a mesh on the right to supply each cell.

Installation

This project comes with a container image which has all required host dependencies installed. Therefore, only the sources have to be locally installed and you keep your host system clean.

Install podman:

sudo apt install podman
pip3 install podman-compose==1.0.6 --user

Build a container:
```
podman-compose build
```

Download all sources:

curl https://storage.googleapis.com/git-repo-downloads/repo > repo
chmod a+rx repo
./repo init -u https://github.com/aesc-silicon/i2c-gpio-expander.git -b main -m manifest.xml
./repo sync

Podman might fail with WARN[0000] Error validating CNI config file... on Ubuntu systems. This can be fixed by manually installing a newer version of containernetworking-plugins:

curl -O http://archive.ubuntu.com/ubuntu/pool/universe/g/golang-github-containernetworking-plugins/containernetworking-plugins_1.1.1+ds1-3build1_amd64.deb
sudo dpkg -i containernetworking-plugins_1.1.1+ds1-3build1_amd64.deb

Register Map

Register	Name	Access	Description
0x0	Value	R	Returns IO value
0x1	Write	R/W	Writes output value
0x2	Direction	R/W	Enables output value

Container

Start the Elements container in the background with following command:

podman-compose up -d

Afterwards, run the following command and replace <target> with one from the Makefile.

podman exec --workdir=$PWD -it i2c-gpio-expander_container bash -c 'make <target>'

FPGA Flow

First, generate the required files for the ECPIX5 Board and afterwards, synthesize it.

podman exec --workdir=$PWD -it i2c-gpio-expander_container bash -c 'make ecp5-generate'
podman exec --workdir=$PWD -it i2c-gpio-expander_container bash -c 'make ecp5-synthesize'

Next, flash the bitstream into the ECP5 FPGA.

podman exec --workdir=$PWD -it i2c-gpio-expander_container bash -c 'make ecp5-flash'

Connect PMOD0 pin 0 (SCL) and pin 1 (SDA) to an I2C Controller (Master) interface.

ASIC Flow

The ASIC flow is similar to the FPGA one. Generate all required files at the beginning and start the chip layout.

podman exec --workdir=$PWD -it i2c-gpio-expander_container bash -c 'make sg13g2-generate'
podman exec --workdir=$PWD -it i2c-gpio-expander_container bash -c 'make sg13g2-synthesize'

Please check Known Issues in case the chip layout failed.

Finally, open the chip layout and inspect the layout with either OpenROAD or Klayout.

podman exec --workdir=$PWD -it i2c-gpio-expander_container bash -c 'make sg13g2-openroad'
podman exec --workdir=$PWD -it i2c-gpio-expander_container bash -c 'make sg13g2-klayout'

Design Rule Checks

The following targets run Design Rule Checks for the chip layout. The first two run the minimal set.

podman exec --workdir=$PWD -it i2c-gpio-expander_container bash -c 'make sg13g2-drc-minimal'
podman exec --workdir=$PWD -it i2c-gpio-expander_container bash -c 'make sg13g2-drc-minimal-gui'

The following two run an enhanced set of rules.

podman exec --workdir=$PWD -it i2c-gpio-expander_container bash -c 'make sg13g2-drc-maximal'
podman exec --workdir=$PWD -it i2c-gpio-expander_container bash -c 'make sg13g2-drc-maximal-gui'

SteffenReith/i2c-gpio-expander