[quote author=Jack Christensen link=topic=143287.msg1077504#msg1077504 date=1358529562]
For the life of me, I can't download the PDF in the original post. I get error 503 from the web site when I click it. Could you post a link to this device?
[/quote] The URL for product info is at: I2C 1KHz to 68MHz Programmable Oscillator. There is a link to the user manual, but the schematic has to be requested via the sales email address. I also get the 503 error when I try to download it. Perhaps its been deemed to be proprietary.
How often will communications be required? I heard a story once about an I2C device that was overloaded by too-frequent bus communication and it affected its internal operation as a result.
This is no longer the problem. Ignore the code in my first post.
Here is the current problem:
The module is sent a count that sets an oscillator frequency. That frequency is determined by the high 14 bits of an unsigned word. The two MSB enable or disable the two clock outputs. The SDA and SCL lines have 4.7K pull-ups, and the waveforms look good on the scope.
The current program sends one oscillator value at setup time. Nothing is sent in the "loop()". The problem now seems that higher values don't get to the module. I have to power down the module and the UNO and then power up the UNO and the module in that order. Once the module powers up, the output goes to the set frequency.
Is 0x2E the write address? Then 0x2F would typically be the read address. The read/write bit is the least significant bit with zero indicating write and one for read. Shifting the address by one bit ( >>1) seems unusual, but without knowing anything about the device or seeing the datasheet, I can't be certain.
This is the technique needed by the Wire library.