pico_pi_controller

A service interface for one or more Raspberry Pi* SBCs to be monitored & controlled by a Raspberry Pi Pico^†, using i2c.

Requirements

Work in progress. See Hardware & Software Instructions below.

1. The RPi* must have GPIO pins 18 & 19 free for use by pigpio as SDA & SCL of secondary i2c controller.
2. RPi4 must have manual installaltion of pigpio for compatible i2c use.
3. Pico^† must be running CircuitPython-6.x.
4. Pico^† must have adafruit_bus_device & pico_pi_controller CircuitPython libraries installed.

* RPi 4/3/Zero, RPi4: GPIO pins 10 & 11; pigpio enables use of the Broadcom SoC secondary i2c controller as a 'peripheral' device.

^† or any CircuitPython-capable MCU.

Install

pip install pico_pi_controller

Hardware & Software Instructions

Quick Start

If using the simple setup of one RPi controlled by a Pico. Additinal RPi may be added by repeating steps 1 & 4.

1. Connect RPi secondary i2c pins to Pico primary i2c pins SDA↔SDA SCL↔SCL GND↔GND:

   1. On RPi*, connect GPIO pins 18 (SDA), 19 (SCL) and GND (any GND pin), e.g. using Female/Female Jumper Wires; color conventions may be found here.
   2. On Pico†, connect wires from RPi (above) to the primary i2c bus, board pins 4 (SDA), 5 (SCL), and GND (any GND pin).

2. Plug Pico into RPi USB port, e.g. using MicroB to USB A cable.

3. From RPi, install CircuitPython & CircuitPython Library Bundle onto the Pico:

   1. On RPi, download CircuitPython & install it on your Pico.
   2. On RPi, download & unzip CircuitPython Library Bundle, then copy from the lib folder adafruit_bus_device to the lib folder on your Pico (CIRCUITPY drive).

4. On RPi, install pico_pi_controller components.

   1. On RPi, install pico_pi_controller (e.g. pip3 install pico_pi_controller)
   2. On RPi, locate‡ & copy ppc-daemon.py to the location of your choice and configure your system(s) to run the script on startup (it's a daemon), then reboot or manually run the daemon.

5. From RPi, install pico_pi_controller for CircuitPython onto the Pico. 2. On RPi, download & unzip pico_pi_controller for CircuitPython, then copy from the lib folder pico_pi_controller to the lib folder on your Pico (CIRCUITPY drive).

6. Unplug the Pico from the RPi USB port and connect it to a reguar USB power source.

* RPi4 uses GPIO pins 10 (SDA), 11 (SCL).

† Other MCU boards will have different pinouts. If using an MCU board with a Qwiic or STEMMA QT connector, e.g. Adafruit Feather RP2040, this cable is useful.

‡ locate the installed files, e.g. in ~/.local/lib/python3.7/site-packages/pico_pi_controller/examples.

How to use

On each RPi, with pigpiod running, run this example ppc-daemon.py script:

import pico_pi_controller

mydevice = pico_pi_controller.PPPeripheral(0x13)

Where 0x13 is the chosen unique I2C address of your RPi on the I2C bus where an MCU controller is running (e.g. a Pico running CircuitPython_pico_pi_controller.

A more sophisticated example:

import pico_pi_controller
import time
import threading
import logging
    
address=0x13
    
def i2c_peripheral(address):
    global mydevice
    mydevice = pico_pi_controller.PPPeripheral(*args, **kwargs)
    logging.info("PPC: starting I2C peripheral ",hex(address))
    
t = threading.Thread(target=i2c_peripheral(address, bosmang=True, UART_TX=8, UART_RX=9, PWR=10, PEN=11)
threads.append(t)
t.start()

while True:
    logging.info("PPC: last controller contact",mydevice.last_contact(),"seconds ago.")
    sleep(1)

When your device declares itself to be bosmang, it sends its own datetime for setting the controller's RTC. Optionally, a bosmang can send commands to the controller, e.g. to reboot or shutdown any connected RPi. Additionally, bosmang may have its console UART, gpio-poweroff, and PEN pins connected to GPIO pins on the controller which enables the controller to execute a safe shutdown & poweroff plus full poweronn of bosmang.