Wednesday, January 10, 2018

Decoding GM's ALDL with Teensy 3.6


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

Diagnosing Watches With Electronics

I've been fascinated by mechanical watches since I was a kid. Little machines on the wrist, marking out the passage of time with an unexpected level of accuracy, at least if the watch is in good shape.

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.

Monday, May 29, 2017

Soothe and Glow doesn't light up


Our little girl goes to sleep easier when we have a Fisher Price Soothe and Glow running. One of them didn't light up, and I fixed it. But not before my wife bought another one. Here's what was wrong.