[time-nuts] dsPICs and GPSDOs
Bob Stewart
bob at evoria.net
Fri Jun 20 15:30:09 EDT 2014
Once I got my TIC going, I suppose it was inevitable that I build a GPSDO with a dsPIC33. I have a few dsPIC specific questions for anyone who designs with them.
1. VCAP. The datasheet says that it should be a surface mount device. I had hoped to avoid those. Can I get away with a 10uf tantalum placed at .1" from the pin? I'm using a 28-pin DIP dsPIC, which will probably be socketed.
2. The datasheet suggests an inductor between AVDD and VDD. Given that I'll only be reading the ADC twice a second (PPS and temps), can I just use the straight wire that I have already penned in? I'm starting to run out of board space.
As to why I'm using a dsPIC: the one I chose has a number of features that suit me, such as 2 UARTs, SPI, buffered ADC, (audio) DAC, and especially relocatable pins. To be honest, I don't know whether this will result in a general purpose GPSDO engine (with sawtooth correction) or a smoke machine, but I'm hoping for the best. I'll try to resist the temptation to make more posts until I have a completed project.
Bob - AE6RV
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