Saturday, June 30, 2018

AD9280 AD9708 AD / DA Module for AX series FPGA Development Board

I keep seeing these AD/DA modules on ebay, (such as this one) but I've not been able to find much  documentation. There's of course the Analog Devices AD9708 and AD9280 spec sheets, but not much else for the board itself.

"The AD9280 is a monolithic, single supply, 8-bit, 32 MSPS analog-to-digital converter with an on-chip sample-and-hold amplifier and voltage reference" ... "The AD9708 (digital-to-analog converter) can support update rates up to 125 MSPS"

When considering a board, the AD9764  14-bit also looks interesting, but it appears to be obsolete. There's a newer AD9246, but I could not find a site that listed the eval board for sale: (e.g. mouser, digikey, etc). In fact, there are a LOT of options: Here's a list of Analog Devices Eval Boards at Mouser. There's also this Precision ADC selector Guide. I'm pretty sure I'm just interested in the ones on page 5: Analog Devices’ single channel successive approximation register. There's kinda no limit to the options, such as this impressive AD9172 Dual, 16-Bit, 12.6 GSPS RF DAC with Channelizers  (spec sheet); yes that's over TWELVE BILLION, 16-bit samples per second. ZOOM!

So many choices... I ended up exhausted trying to find something with a high sampling rate, and a large bit width, and a low cost for simply experimenting. So in the end the 8 bit dual AD and DA on one board for about $20 bucks was hard to beat.

For this board, I've found two different pin numbering schemes: one that uses the traditional left-right, 1-2 number used in most ribbon cables, (so that the ribbon cable wires are sequentially numbered)... and I would think that this is the correct pin numbering:

However I also found this somewhat "DIP-style" numbering used on integrated circuits, running sequentially down one side, then the other (although the numbering is reversed on the second column). I'm hoping this is not the correct wiring, but I will not know for sure until my board arrives.:

See video clip here.

They seem to be in agreement with pin number (e.g. Pin 5 is DA CLK)... but the point is: where exactly is that pin on the header?

I did eventually find this interesting article from Hackaday regarding using this board to build a software defined radio for the Raspberry Pi using the Icoboard plug-in with a Lattice iCE FPGA  (this may tie in well with my recent iCE40UP5K-B-EVN purchase!) The the icoboard is for sale here, for about 80 euro. Note for that price you also get 8 mbit of RAM on the back of the board!

Info starting here in the video.

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