Table of Contents
Telemetry System
The new telemetry system uses a Raspberry Pi to collect CAN messages from the vehicle along with metrics such as GPS coordinates. We use Node-Red to collect this data and also send it to FRED’s Node-Red which will store our data in the cloud and allow us to pull data from InfluxDB which is hosted by FRED. We also have a DBC file that helps us translate what each CAN message-id and data mean.
Setup
The link below shows how to generate the DBC file used to translate all the CAN messages.
https://uwmidsun.atlassian.net/wiki/spaces/ELEC/pages/1395032080/Telemetry%2BSet%2BUp
FRED
Link to FRED. This is the system we will be using that hosts Node-Red and InfluxDB on the cloud.
Multiple Network Interface Traffic (Multihoming)
We can set up the Raspberry Pi such that we can send data over both LTE and wifi depending on the location of the vehicle and our situation. We can set this up on the Pi by following instructions provided here or read the short version below.
Assign each interface IP address using ifconfig to set up multihoming.
Example:
ifconfig eth0 192.168.1.254 upifconfig eth1 192.168.2.254 up
Aggregating Data
Since there is a flutter app that analyzes the CAN data and provides us with metrics on the vehicle, we need to be able to send WebSocket messages to the flutter app which can be set up through Node-Red. However, we also need to format these WebSocket messages as a JSON as shown below.
CAN Messages
Property | Sample Value |
|---|---|
Datetime | 2020-01-20 03:14:07 |
Name | MOTOR_CONTROLLER_VC |
Sender | MOTOR_CONTROLLER |
Data | {'mc_voltage1':1234, ‘mc_current1’:1} |
GPS Data
Property | Value | Decoded |
|---|---|---|
Datetime | 030620 044747.0 | June 3, 2020 4:47:47.0 |
Latitude | 3722.117666 | 37° 22.117666' |
Latitude Direction | N | North |
Longitude | 12200.011971 | 122° 00.011971' |
Longitude Direction | W | West |
Altitude (meters) | 11.6 | 11.6 |
Speed (knots = 1.852 km/h) | 0.0 | 0.0 |
Course (degrees) | 0.0 | 0.0 |
The aggregate_can_data.py script allows us to grab data from the CAN bus, decode the message with our DBC file, write to a CSV, send to FRED with MQTT, and send to DynamoDB.
The GPS.py script allows us to grab GPS data from the vehicle.
Storing Data on the Raspberry Pi
In terms of storing data locally on the Raspberry Pi, the Python script aggregate_can_data.py can directly output the data to a CSV file locally on the Raspberry Pi. These files can be manually moved to Google Drive if necessary.
