September 7, 2011
about 3 years ago
I’ve built up six of these shields using the Arduino UNO and after making the diode mod (later followed by the FET mod) I have had excellent results. The command set to fully utilize this device is complex and the learning curve is steep but after a few weeks I have a good handle on it. Which brings me to my problem…..
This is a snap to bring up on the UNO, but I wanted to do something more elaborate that required more horsepower. Decided to use the Mega (Arduino with ATMega 2560). The Mega has worked fine for me on previous projects but has basically stumped me with regard to interfacing with the Si4735 shield. At first, it appeared that the only real difference is in the SPI pins - instead of 10, 11 12, 13 the Mega uses 50, 51, 52 and 53. However I set up two different Megas and two different 4735 shields and neither has worked properly. I have rechecked everything many times and have no wiring errors I know of. I have rewritten the Si4735 library substantially in the last few weeks so it is now portable to a variety of environments. The code has worked well with the UNO and I have several of these little guys in the field doing frequency monitoring and have had zero problems.
I have tried the 4735 shield mounted on the Mega (be sure not to use the AREF pin!) and also standalone on a breadboard. Signals are weak, tuning is very flaky and audio it terrible. But put the same shield on the UNO and everything flies.
After some close examination of the Mega schematics and digging into the 2560 manual I have not found any discrepancies that would prevent this setup from working.
So, has anyone done this, and is their a trick, or is this project just snakebit?
By the way, I’d love to get with the guy who laid out the 4735 board and give him the list of mods I do to make the board perform much better…. he’d have a butt-kickin' rev 2…
Ron in Texas
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