[time-nuts] Simple open source microcontroller solution to tune DDS needed

[jimlux]

On 12/13/17 1:28 PM, Jerry Hancock wrote:
> Well, if you haven’t selected a DDS and you need I/Q, I would go with the tried and true 9854 as it has I/Q outputs and I thought a 12bit DAC so the resulting spurs and sfdr are lower than other chips, or were, as I think they have 14bit DACs on other chips now.  It also depends on the highest frequency range needed and power requirements as they all seem to run hot.  There is a new DDS, a 9910 I think, that uses a 14bit DAC but it is a single output and would need to sync clocks if you need I/Q.  I have used the 9854 with PIC, Arduino and STM32 and assuming the frequency range is ok, I found it to be the better of the chips.  I don’t think they have a replacement for it (I/Q with 14bit DAC would be great) but I haven’t looked lately.
> 
> The language is C but I think it has C++ and C# compilers out there.  Also, once you have the code tested on the Arduino you can just run it on the equivalent AVR chip and build your own board.  I don’t think there is a license or runtime compiler issue and if there is, I remember seeing a GNU compiler for the AVRs and Arduino.  My only point is that for prototyping and testing, the Arduino seems to be the easiest with tons of support and many, many adapters and I/O,  The STM32 boards are faster but the learning curve is just unbelievable.  It took me months to master those boards compared to minutes for the Arduino.
> 


I agree - $20 for a Teensy, some jumper wires from solder holes on the 
Teensy to your breadboard, load up the Teensyduino libraries into the 
Arduino IDE and your SPI/I2C/serial interface is done.  I did this to 
write arduino code to drive a Silabs part.

If it takes an hour, I'd be surprised (or you have an incredibly slow 
download connection, like doing it on an airplane in the back rows where 
the WiFi is clunky - which I have done).  The hard part when going to a 
standalone design is picking the right pins on the microcontroller 
(since so many have multiple functions, you want to be careful about 
accidentally using something that has another useful function).