Getting Started with pyCRUMBS

pyCRUMBS enables I2C communication between Raspberry Pi and Arduino devices using a structured 31-byte message protocol that now includes a CRC-8 checksum for each frame.

Installation 

git clone https://github.com/FEASTorg/pyCRUMBS.git
cd pyCRUMBS
chmod +x setup_pycrumbs.sh
./setup_pycrumbs.sh

Test: ~/test_pycrumbs.sh

Manual Setup

See Manual Setup Guide.

Development 

pip install -e . --config-settings editable_mode=compat

Basic Usage 

from pyCRUMBS import CRUMBS, CRUMBSMessage

crumbs = CRUMBS()
crumbs.begin()

# Send message
message = CRUMBSMessage(
    typeID=1,
    commandType=1,
    data=[25.5, 50.0, 75.5, 100.0, 0.0, 0.0, 0.0],
)
crumbs.send_message(message, 0x08)

# Request response
response = crumbs.request_message(0x08)
if response:
    print(f"Data: {response.data}")

crumbs.close()

Message Format

Field Type Description Range
typeID int Message type 0-255
commandType int Command ID 0-255
data List[float] Seven floats (payload) IEEE 754
crc8 int CRC-8 checksum 0-255

The library automatically calculates and appends the CRC when sending messages. The crc8 field is exposed so received frames can report the checksum that was validated.

CRC-8 Support

To build the optional native CRC-8 helper (recommended for performance), generate and compile the shared library from the project root:

python scripts/generate_crc8_c99.py
python scripts/compile_crc8_c99.py

If the compiled library is unavailable, pyCRUMBS falls back to a pure-Python CRC implementation at runtime.

Hardware

Wiring 

Pi GPIO 2/3  Level Shifter  Arduino A4/A5
3.3V/5V/GND  Level Shifter  Arduino VCC/GND

Addresses

  • Valid: 0x08-0x77
  • Arduino: Wire.begin(0x08);

Troubleshooting

Permission errors: sudo adduser $USER i2c && sudo reboot

No devices: i2cdetect -y 1

Import errors: Run from parent dir: python -m pyCRUMBS.examples.leader_example

Debug: logging.basicConfig(level=logging.DEBUG)

Error Handling 

try:
    if crumbs.send_message(message, address):
        response = crumbs.request_message(address)
        if response and response.errorFlags == 0:
            return response.data
except Exception as e:
    print(f"Error: {e}")

Resource Management 

from contextlib import contextmanager

@contextmanager
def crumbs_connection():
    crumbs = CRUMBS()
    try:
        crumbs.begin()
        yield crumbs
    finally:
        crumbs.close()

with crumbs_connection() as crumbs:
    # Use crumbs here
    pass

Next Steps