Archive for May 18th, 2017
Compare this picture:
… with any of the doc for the generic AD8950/51 DDS modules you’ll find out on the Interwebs. This snippet from the seller’s schematic will suffice:
Here’s a closer look at the 2×7 header in the upper left corner:
Don’t blame me for the blur, the schematic is a JPG.
Compared it with the board in hand:
Yup, the D7 and GND pins are reversed.
Some careful probing showed the silkscreen is correct: the pins are, in fact, correctly labeled.
Should you be laying out a PCB in the expectation of using any DDS module from the lowest-price supplier, remember this high truth: Hell hath no fury like that of an unjustified assumption.
Fortunately, I’m hand-wiring the circuit and caught it prior to the smoke test.