Wednesday, January 10, 2018
I want to log my Jeep's Engine Control Module (ECM) diagnostic data reliably and inexpensively any time the vehicle is running so I can tune it to pass emissions tests and reduce pollution.
To do that, I am using a new Teensy 3.6 microcontroller to first decode the data stream out of the ECM and then store it on a microSD card for later retrieval.
My Jeep is running a retrofitted General Motors #1227747 ECM, which is the brains of a mid-80's Throttle Body Injection (TBI) system found on Chevy and GMC trucks.
The ECM, which predates OBDII systems, spits out a serial data stream called Assembly Line Diagnostic Link (ALDL) at 160 baud. This data stream protocol is nothing like plain old RS-232 serial protocol, however...
Monday, July 10, 2017
To measure accuracy and diagnose issues, watchmakers use a watch timer which listens for and measures intervals between ticks. However, the tools are rather expensive for hobbyists, such as yours truly.
Fortunately, free or low-cost options like Watch-o-Scope ease the burden, but require a sensor and preamplifier. Here's my take on this fun little preamp project.