Service port on espresso machine

Hi Folks,

Yesterday I discovered a service port on my Bosch Espresso machine. I was wondering how I can use that port and maybe use an arduino (+ twitter) to make a cup of coffee for me!

So I started by investigating the wires, there are 4 wires. The connector is the same as a floppy drive power connector from the days. I started measuring the voltage between the wires, there is one ground, and between the ground and the other 3 wires there is an voltage difference of 5 volts.

How can I figure out the type of connection? JTAG usually works at 3.3 volts right? Can it be some kind of serial? How do I find the right baud rate?

Cheers! Chris

PS: It's a Bosch benvenuto B30

Try to find a service manual for the machine. There is no reason why there should be the ability to make the machine make coffee via the service port though. It might well just be a diagnostic port.

JTAG, not available on '328's, but available on '1284s on PC2,3,4,5, would follow the Gnd to VCC = 1.8V to 5.5V. See page 87 and 268 of the '1284 data sheet.

You can look at the signals with an oscilloscope to make a determination of bit High/Low times and estimate the baud rate. Once known, connect Gnd and 1 signal at a time to the Rx pin, and see if recognizable 8-N-1 characters are coming in send them to the serial monitor.