Detector App freezes when starting FRAM while LMIC driver is in operation

[dniklaus]

Actual Behavior Adafruit FRAM I2C driver start renders the detector firmware application to be freezed while LMIC driver (LoRaWan RFM95 module driver) is in operation.

Expected Behaviour The operation of all drivers must be possible w/o any interferencing issues.

Steps to reproduce

1. Run the Detector FW with the LMIC driver in service
2. Start I2C Bus (Wire.begin())
3. Heartbeat LED stops blinking, CLI on USB Serial shows no reaction

Possible Workarounds

• for the MVP (2 detector nodes, we prepare 5 nodes), use a GPIO 3 bit wired device ID to distinguish between the devices, provice hard coded TTN Keys for all 5 nodes and provision the device's own tuple according to the GPIO 3 bit device ID, GPIO bits (#37):
  • Bit 0: Pin A0 (14)
  • Bit 1: Pin A1 (15)
  • Bit 2: Pin A3 (16)
• try to use SPI instead of I2C bus, replace the Adafruit FRAM I2C by an Adafruit FRAM SPI
• review the I2C HW, especially pull-up resistors (4k7), consider also other potential error sources as mentioned here: https://github.com/arduino/ArduinoCore-samd/issues/194#issuecomment-269444283

[dniklaus]

@ithuerin have you already started working on this?

[dniklaus]

@ithuerin The workaround (first point mentioned above) is implemented now (available in master branch).