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dds + pic
Has anybody here attempted to use a pic to control a dds chip (and
wrote the software himself)? I was looking at G3XJP's article on his 'pic-n-mix' vfo using an 16C84 to control an AD9850. I can't belive he was able to get all that functionality into just 1k of code and 64 bytes of eeprom. (you can find his article as an apnote on the Analog Devices web site ... AN-557 is the number) I'm thinking of using the AD9954 dds chip instead of the 9850. I'm just starting to look at what's required in code to get from a BCD input to the DDS word. Keep in mind G3XJP didn't hard code his clock as a constant, it can be adjusted. The formula to get the DDS word involves some math with fractional parts, it can be done in interger math with some scaling or lookup tables, but there isn't much room in a pic. I just ordered some 16F88's with 4k of program space and 256 bytes of eeprom so I would have a little more room. Any starting ideas would be welcome! |
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