History

rbaron e32803d44d Improvements to photo resistor-based lux estimation - Code now compiles - Estimation of the photo resistor resistance works - Lux estimation from the photo resistor resistance needs more work and calibration - Lux is now encoded in the BLE advertisement payload		2021-09-22 22:38:30 +02:00
..
config	Improvements to photo resistor-based lux estimation	2021-09-22 22:38:30 +02:00
src	Improvements to photo resistor-based lux estimation	2021-09-22 22:38:30 +02:00
.gitignore	Initial b_parasite code - a fork from playground	2021-03-13 14:56:37 +01:00
b_parasite_gcc_nrf52833.ld	Add support for nrf52833 based module	2021-09-02 15:40:19 +02:00
b_parasite_gcc_nrf52840.ld	Add support for nrf52833 based module	2021-09-02 15:40:19 +02:00
Makefile	Fix indentation and default value for PLATFORM	2021-09-02 19:46:10 +02:00
README.md	Fix typo in code readme	2021-09-02 20:02:24 +02:00

README.md

Overview

This is the b-parasite formware based on Nordic's nRF5 SDK.

It uses Nordic's SoftDevice, which should additionally be flashed to the chip before running our firmware.

I use a JLink probe for flashing and debugging.

Configuration

The b-parasite specific configuration, such as active/sleep time and transmitting power are defined in config/prst_config.h.

Flashing SoftDevice and Firmware

# Flash softdevice
$ SDK_ROOT=~/dev/nrf52/sdk/nRF5_SDK_17.0.2_d674dde make flash_softdevice
# Compile annd flash our firmware
$ SDK_ROOT=~/dev/nrf52/sdk/nRF5_SDK_17.0.2_d674dde make flash

Debugging

Calls to NRF_LOG will be readable on the console using JLinkRTTLogger. This is the handy one-liner I use for pulling log messages:

$ echo "\n\n\n\n0\n/dev/stdout" | JLinkRTTLogger | sed 's/^.*app: //'

Bluetooth Low Energy Advertisement Data Encoding

Sensor data is encoded in the BLE advertisement packet as Service Data for the Environmental Sensing Service profile (UUID 0x181a).

Sensor data is encoded in unsigned 16 bits (2 bytes), and whenever multiple bytes are used to represent a single value, the encoding is big-endian.

Byte index	Description
0	4 bits for protocol version + 4 reserved bits
1	4 reserved bits + 4 bits wrap-around counter for deduplication
2-3	Battery voltage in millivolts
4-5	Temperature in millidegrees Celcius
6-7	Relative air humidity, scaled from 0 (0%) to 0xffff (100%)
8-9	Soil moisture, scaled from from 0 (0%) to 0xffff (100%)
10-15	b-parasite's own MAC address, big-endian format

Supported Modules

This code supports two E73 modules:

E73-2G4M08S1C (nrf2480, default)
E73-2G4M08S1E (nrf2833)

To choose for which one you want to compile, just pass PLATFORM as an env variable to make, and set it to the platform you want to use. For example, to compile for E73-2G4M08S1E:

SDK_ROOT=<...> PLATFORM=E73_2G4M08S1E make

and vice-versa for E73-2G4M08S1C, although that platform will be chosen as default anyways:

SDK_ROOT=<...> PLATFORM=E73_2G4M08S1C make