Pico I2C Probe

An I2C probe based on the Raspberry Pi Pico

• Pico I2C Probe
  • What is it?
  • Features
  • The interface
    • USB
    • JSON
      • Sample schema
      • Structure
      • Actions schema
        • Scan
        • Check for device
        • Write data
        • Read data
        • Write then read
        • Repeat

What is it?

The Pico I2C Probe is a simple device meant for testing an I2C bus with various writing, reading, and scanning capabilities

Features

• Set bus speed
• Scan
• Check for specific address
• Write data
• Read data
• Write then read

The interface

All I2C communication occurs on pins GP4 (SDA) and GP5 (SCL). Ensure there is a pullup resistor on each of the two lines.

USB

An interactive, imperative CLI that lets users execute specific actions over USB. ⚠️ Not implemented!

JSON

A JSON file with the name of actions.json can be dropped to the Pico from a host device which executes each command in order and prints the results to the terminal over USB.

Sample schema

{
    "config":
    {
        "bus_speed": 100000,
        "default_address": "0x02",
        "default_delay": 5
    },
    "steps":
    [
        {
            "action": "WRITE",
            "data": [2, 3, 50],
            "delay": 10
        },
        {
            "action": "REPEAT",
            "times": 10,
            "delay": 20,
            "steps":
            [
                {
                    "action": "READ",
                    "bytes_to_read": 1
                },
                {
                    "action": "CHECK_ADDR",
                    "address": "0xa2"
                }
            ]
        },
        {
            "action": "WRITE_THEN_READ",
            "data": [10],
            "bytes_to_read": 1
        },
        {
            "action": "WRITE",
            "address": "0x1f",
            "data": [23, 255]
        }
    ]
}

Structure

The first key is config, and it supports the following keys:

Key	Type	Default	Description
bus_speed	number	100000	Bus speed in Hz
default_address	string		Address of the default address in HEX; will be used when address not present in an action
default_delay	number	0	Delay after each action in ms; will be used when delay not present in an action

The second key is steps, and it is an array that contains a list of actions to perform sequentially

Actions schema

Scan

Key	Type	Value	Optional	Description
action	string	"SCAN"	No	Scan the bus for devices
delay	number	Delay in ms	Yes	Delay after action
log_message	string		Yes	Print message to terminal before execution of action

Check for device

Key	Type	Value	Optional	Description
action	string	"CHECK_ADDR"	No	See if device exists at address
address	string	Address in HEX	Yes	Address to check
delay	number	Delay in ms	Yes	Delay after action
log_message	string		Yes	Print message to terminal before execution of action

Write data

Key	Type	Value	Optional	Description
action	string	"WRITE"	No	Write bytes to address
data	array of number	[byte, byte, ...]	No	Array of bytes to send
address	string	Address in HEX	Yes	Address which receives written data
delay	number	Delay in ms	Yes	Delay after action
log_message	string		Yes	Print message to terminal before execution of action

Read data

Key	Type	Value	Optional	Description
action	string	"READ"	No	Read bytes from address
bytes_to_read	number		No	Number of bytes the host expects to receive
address	string	Address in HEX	Yes	Address which sends data
delay	number	Delay in ms	Yes	Delay after action
log_message	string		Yes	Print message to terminal before execution of action

Write then read

Key	Type	Value	Optional	Description
action	string	"WRITE_THEN_READ"	No	Write bytes followed by immediate read from address
data	array of number	[byte, byte, ...]	No	Array of bytes to send
bytes_to_read	number		No	Number of bytes the host expects to receive
address	string	Address in HEX	Yes	Address to check
delay	number	Delay in ms	Yes	Delay after action
log_message	string		Yes	Print message to terminal before execution of action

Repeat

Key	Type	Value	Optional	Description
action	string	"REPEAT"	No	Repeat the action n number of times
steps	array of action		No	List of actions to repeat
times	number		No	Number of times to repeat repeat_action
delay	number	Delay in ms	Yes	Delay after each action
log_message	string		Yes	Print message to terminal before execution of action