The software will be on a PIC microcontroller - they are obviously much smaller than a Raspberry Pi and use a lot less power! I am using the PIC16F690 coz this is the one on the "low pin count" demo board that comes with the PICkit2 programmer. The plan is to use the PIC16F913 as this has LCD driver capabilities.
The basic functionality will be the same:
- Receive call from GSM module
- Decode and dial number from rotary dial
- Place call with AT command on GSM module.
I have made a start by buying a new GPO phone:
...and a GSM module...
This will be incorporated with the new ringer module - yet to be built. The original mic/speaker will be replaced with some more modern 8ohm ones - should give a clear sound.
I've also completed the C code to decode the dialling and produce the AT command. I've been testing this with an RS232 to USB cable into my Win7 laptop using RealTerm. The AT command is just the unaltered output from the PIC16F690's UART TX PIN. When I was researching this I was under the impression that I needed a MAX232 to produce a text string that could be read by RS232.
I haven't tried to simulate any RS232 input to the PIC yet - this may require a MAX232 - one on order just in case!
C code to follow - it's not as nice as Python (or Java!)
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