Build your own MARES dive computer IRIS interface for RS232
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Why pay up to 100 Euro for an IRIS interface when I can use a soldering iron. Thanks to the info at I started building my own interface. But I soon ran into a problem. You need a TSOP4156 which can be a tough one to get or expensive to buy. I had plenty of old BPW41 Infrared diodes so I decided to build my own receiver. The power comes from the RS232 port, make sure you have at least 5.5 Volts or the 4001 will not oscillate well at 3.6 MHz (Maybe you can get it to work at 5 Volts by adjusting some components. My Laptop can just manage 5.5 Volts so I was OK. The logic chips are good old CMOS so no need to regulate to 5 Volts, more money saved. Also I found the RESET circuit of the 4040 "over the top", changing this saves yet one more NOR circuit. This circuit is realy the bare minimum in my opinion when you do not want the TSOP.

Schematic Circuit for a 9 pin RS232 version, keep RS232 leads short:

MARES IRIS schematic circuit
The above circuit can be optimized for low voltages by changing the 470k resistor to 100k and removing the right 33pF capacitor connected to the 2k2 resistor in the oscillator (which is what I have done). Now it oscillates down to 4 Volts but the frequency is not quite right, which is not important. Adjust the 10K trimmer for 28% of the supply voltage to obtain optimal receive bit timing. My final prototype fits in a mouse.
Mouse inside
Mouse with Dive ComputerFront of Mouse
The Software can be found on the MARES website. If like me you are a happy owner of an M2 RGBM then just pretend you have an M1 and happy dive log downloading!