PCA9615

📒 Datasheet

This repository is an atopile module for the PCA9615, 2-channel multipoint Fast-mode differential I2C-bus. In other words, it lets you use I2C like you might use MODBUS, ie. over long wires and through noisy environments.

🏁 Get started

Installation

From inside a project directory terminal: ato install PCA9615-ato

Code

from "pca9615/elec/src/pca9615.ato" import PCA9615
from "generics/interfaces.ato" import DiffPair, Power, I2C, GPIO

module Test:
    # define virtual buses, connect these to physical components/pins
    power = new Power
    d_sda = new DiffPair
    d_scl = new DiffPair
    i2c = new I2C
    power_a_2v3_5v5 = new Power
    power_b_3v0_5v5 = new Power
    differential_side_power = new Power
    en = new GPIO

    # define the PCA9615
    pca9615 = new PCA9615

    # PCA9615 enable pin is driven high be an internal pullup
    # to disable chip, drive low
    en ~ pca9615.en

    # connect power to normal I2C side
    power_a_2v3_5v5 ~ pca9615.power_a_2v3_5v5

    # differential power can be seperate or the same as the I2C side
    pca9615.power_b_3v0_5v5 ~ power_a_2v3_5v5
    # - or -
    pca9615.power_b_3v0_5v5 ~ differential_side_power

    # normal I2C connection
    i2c ~ pca9615.i2c

    # differential pairs
    d_sda ~ pca9615.d_sda
    d_scl ~ pca9615.d_scl

🤔 Design Considerations

• d_sda and d_scl must be routed as differential pairs (6 in KiCAD PCB Editor)
• power on the I2C side can be separate from the differential side, common grounds are not required
• the I2C side can accept between 2.3 - 5.5 volts
• the differential side can accept 3.0 - 5.5 volts
• an RJ45 connector and CAT6 cable work well for making the connections

🔌 Connections

MCU		MCU PCA9615		Sensor PCA9615		Sensor
		MCU PCA9615.d_SDA 🟩	~	🟩 PCA9615.d_SDA	~
		MCU PCA9615.d_SCL 🟪	~	🟪 PCA9615.d_SCL	~
MCU.SDA 🟨	~	🟨 PCA9615.SDA 🟨		🟨 PCA9615.SDA	~	🟨 Sensor.SDA
MCU.SCL 🟦	~	🟦 PCA9615.SCL 🟦		🟦 PCA9615.SCL	~	🟦 Sensor.SCL
MCU.VCC 🟥	~	🟥 PCA9615.VCC 🟥	(optional)	🟥 PCA9615.VCC	~	🟥 Sensor.VCC
MCU.GND⬛	~	⬛ PCA9615.GND ⬛	(optional)	⬛ PCA9615.GND	~	⬛ Sensor.GND

⚡ Programming

Once connected, the sensor (or just the other side) appear as a normal I2C device to the host. Nothing special needs to be done.

🙏 Contributing

This design is intended to be a community best-effort at a minimal circuit combining:

• datasheet reference design
• readily available components
• modular and reusable layout

You are greatly encouraged to contribute or discuss any improvements here so that everyone may benefit.

License

CERN-OHL-P v2