DAC8734EVM: Trouble with SPI communication

Russ Walker

Part Number: DAC8734EVM

Hi, using 3v3 microcontroller with SPI clock at 500kHz for debugging. Clock idles low. Data changes on rising edge. Here is sample logic trace:

Board jumpers are in default positions. Gain of 4 on DAC channels. /LDAC is pulled low. Hardware /RST is not pulled low. Ref voltages check good on board.

Cannot control GPIO channels, they remain hi, or drive DAC values, they remain at zero. Default startup command used is 0x00, 0x02bc. Command used to set DAC0 to 0xf000 is 0x04, 0xf000.

GPIO's remain hi and DAC's remain at zero.

Thanks for any help.

over 7 years ago

0 Russ Walker over 7 years ago

Prodigy 30 points

Found a YouTube video, www.youtube.com/watch, that indicated the MOSI line was on the bottom connector of the board and not the top. Problem solved. I re-read my user guide, dated September 2010. I do not see that crucial information there.

0 Kevin Duke over 7 years ago in reply to Russ Walker

TI__Mastermind 46290 points

Russ,

First - I apologize for the delayed response. Our ordinarily assigned Engineer for this product was unavailable recently and therefore we did not get you a response on Monday.

Thank you for joining the E2E Community and please let us know if there is anything else we can help you with.

0 Uttam Sahu over 7 years ago in reply to Kevin Duke

TI__Genius 14220 points

Hi Russ,

I am assuming that you must be using external power supplies to drive the EVM as you are using a microcontroller to drive it instead of the motherboard. It would be a godd idea to understand whether all power supplies are correct or not, especially the IOVDD. Could you measure them and let us know?

Regards,
Uttam Sahu
Applications Engineer, Precision DACs

0 Russ Walker over 7 years ago in reply to Uttam Sahu

Prodigy 30 points

Hi Uttam,

Please see 1st reply above, problem is resolved. The issue was the location of the MOSI pin. It is on J2.11 ONLY on the underside of the board.

I am using 3v3 IOVDD. JP8 is set correctly. I've been able to drive the SPI clock to 15Mhz, but not higher. This is not an issue at this point.

Thank you,

-Russ

0 Uttam Sahu over 7 years ago in reply to Russ Walker

TI__Genius 14220 points

Thanks a lot, Russ for the confirmation. I somehow got confused.

Regards,
Uttam

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DAC8734EVM: Trouble with SPI communication