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magene

6 Posts
Posted - 13 Jun 2008 :  11:57:44  Show Profile
I'm using SSP3 on my Bitsy Xb to talk to a TI ADC1271 ADC. I have to put SSP3 into the PSP mode because the TI implementation of SPI is not the same as the PXA270 SPI. To make a long story short, the SCLK line out of the Xb looks very odd at high speed. The shape is triangular and as the frequency increases the whole clock signal gets more and more offset from ground (0VDC). I can provide scope shots but I'm wondering if you can tell me if J3-39 (and any of the other SPI signals) are connected to anything else on the Xb board. It is only driving a short piece of wire and one 74AVC load on my side.

Thanks - Gene Massion


akidder

1519 Posts
Posted - 13 Jun 2008 :  15:59:03  Show Profile  Email Poster
Hi Gene. The problem is likely that the series resistance in on the BitsyXb side is too high for your application. (I'm posting an erratum about this to the BitsyXb user manual at topic 2096.)

Drop us a line at support.us@eurotech.com and we can work with you to replace the resistor pack to see if helps in your tests.
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