The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

The New Hotness

  • Generic AD9850 DDS Modules: Beware Swapped D7 and GND Pins!

    Compare this picture:

    AD9850 DDS Module - swapped GND D7 pins
    AD9850 DDS Module – swapped GND D7 pins

    … 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:

    AD9850 module schematic - cropped
    AD9850 module schematic – cropped

    Here’s a closer look at the 2×7 header in the upper left corner:

     

    AD9850 module schematic - J5 detail
    AD9850 module schematic – J5 detail

    Don’t blame me for the blur, the schematic is a JPG.

    Compared it with the board in hand:

    AD9850 DDS Module - swapped GND D7 pins - detail
    AD9850 DDS Module – swapped GND D7 pins – detail

    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.