Datalogger - more updates

Tuesday, July 25, 2017 - 15:00

It's been about six weeks since I posted the last update to the site, so thought I better post something...

Since the last post I've been working on implementing a modular system, with the idea that the basic logger can handle control inputs from USB, Bluetooth LE, a simple stop/go button interface, or a touch panel. The "Pass Through" interface shown in the last post is intended as a way of allowing applications running on mobile devices to communicate with the ECU without the need to micro-manage the low level protocol. You send a Service ID, Resource ID and any other necessary data for the request and get back a positive response plus data, or negative response if the request fails.

The second module is a configurable logger. And this is what I've been working on since start of July. The logger is currently set up with definitions for the 18 or so diagnostic requests that I think you'd realistically want to log.
Requests are set by using something like..

AT M LC  09 0D 1B

LC indicates a "Log Configure" command, and the items to log are specified using the Request ID. In this example 0x09 = RPM, 0x0D = Road Speed, and 0x1B = Throttle Voltages. The command input is not case or space sensitive.

Starting and stopping logging is controlled by AT commands.


These are the "Log Start" and "Log End" commands respectively.

By default the data from the logger is in ECU format with no transformations. Using the LR command


toggles between "Raw" and "Convert" mode which converts Kelvin to Celsius and shifts decimal places where appropriate.

The next thing I need to tackle is the logging to SD Card and the button control interface.