Turns out that there were two problems, one of which was mine (more about the other one further down). Another weeBell user reached out because he was having echo problems and this started me looking at the code again in my off hours. I shorted some testing in my rush to get the 1.0 firmware release out (because I was going to soon be busy with other projects) and of course it came back to bite me. I'm sure if I did a search I'd find an axiom that says something about version 1.0 of any software needing to be followed with another version. The bridge rectifier and ESD suppressor shunt excess voltages to ground. Here's the output circuitry on the initial revision of the PCB. What is neat about this is that you can connect weeBell to the existing wiring in a building (disconnecting it outside the building!!!) and then plug up to three POTS phones into other outlets on the same circuit. It can handle typical induced spike voltages but can't handle a lightening strike like telephone company line cards could. But that wiring is meant to be "on-premise", meaning within one building. There is some additional protection circuitry since the AG1171 is specified to drive up to 1 km of wiring. I briefly thought about trying to design my own analog circuitry because the AG1171 had gotten a lot more expensive but quickly realized best to leave this to the professionals. It adapts the audio to and from the codec to the telephone line, generates ringing voltages and can detect hook actions (used to determine off-hook condition and rotary dialing). The hybrid function is once again provided by the Silvertel AG1171 SLIC module. I started with the NXP SGTL5000 Codec chip, mainly because I had one laying around on a PJRC Audio shield. It took me weeks of effort to understand how I could reproduce my original gadget because I had to learn about the Espressif Classic Bluetooth library (with detours to Bluekitchen's BTstack and Espressif's ADF and back), and figure out how to deal with things like echo cancellation (thankfully I could stand on the shoulders of some real experts, like Dave Rowe and Steve Underwood, who shared their telephony code).įinally I had a rough prototype running and could design a new PCB to hold the telephony components. I started with the bluetooth implementation. Or maybe messages could be left for others to discover (lol, maybe this wouldn't be a good idea for the general public.) Different messages could be reached by dialing different numbers.
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