PCR-100 modified for TTL serial

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jonny290

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I was bored last night so I modded my PCR100 for TTL serial i/o.

I have an ongoing project with these and wanted to see if I could get them talking to my Arduino without going and spending money on MAX232's. I reasoned that nothing really 'talks' RS232 internally, and that it must be level-converted inside the radio. I found the RS232 converter, IC9, and found that it goes into a disable state whenever the STBY pin is brought low. This is pulled to ground by a 100k resistor and pulled up by +5V from the CPU, through a diode.

I located the diode, D87. It is a small three terminal diode. I carefully lifted one side but left it in place, though I should be able to replace it with any SMT diode later. After that it was just a matter of pulling TTL serial TX/RX off pins 49 and 48 of the CPU, respectively. These pins are both at a corner and are easy to solder to.



Then you'll need to connect to your microcontroller, open the serial port at 9600 and send/receive commands and data. The only hitch so far is that I can't reflash the Arduino with the PCR connected, as it uses those serial pins for programming. I have enough code written to turn it on and tune to a pre-programmed station. :)


I suspect that at least the PCR-1000 is built similarly, and should be easily interfacable to TTL logic without the added expense and hassle of level converters.
 
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SCPD

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I suspect the 5 volt TTL from the Arduino is strong enough to drive the '100's line driver input. A 5 volt Zener diode and resistor would protect the Arduino from the line driver output while allowing both to communicate.

Might be worth a try (and would avoid SMT surgery on your '100).
 

ctripps

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Jun 13, 2007
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Nicely done!

Now I need to find a way to insert a keepalive signal so the PCR doesn't stop working when disconnected from the serial port.

Andy
 
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