Problem using AD5270 digipot -SOLVED - Page 1
Forum section: electronics / projects

author: dzseki
author_rank: Frequent Contributor
timestamp: June 05, 2024, 03:21:44 pm
content: Does anyone else using AD5270 digital-potentiometer? I would, but I have problems.I think I am sending out the right commands through SPI, yet the resistance just stuck at midpoint. Normally I would think the IC is faulty, but I have two identical boards behaving exactly the same way. I have a third (yet unpopulated) IC, but since they came from the same source, same reel, I am not very excited to replace it.I even made two scope shots for you, one with zero-wiper and the other with full-open wiper setting, the device just stuck at midpoint.Am I missing something obvious?

author: jwet
author_rank: Frequent Contributor
timestamp: June 05, 2024, 04:50:02 pm
content: Your SPI writes do seem correct to me. This is an unusual device- its not a pot with a wiper and two ends, its actually a resistor with a wiper and one end. Are you measuring "ohms" or somehow reading like a resistor?

author: ArdWar
author_rank: Frequent Contributor
timestamp: June 05, 2024, 05:08:04 pm
content: How's your device initialization? Do you properly disable write protection?

author: dzseki
author_rank: Frequent Contributor
timestamp: June 05, 2024, 10:07:40 pm
content: Quote from: ArdWar on June 05, 2024, 05:08:04 pmWhat initialization do you mean? From my understanding I should just send whicever "command" I like to the device. In this case I don't want to use the memory function, I only want to operate with direct RSET (command 1)

author: Benta
author_rank: Super Contributor
timestamp: June 05, 2024, 10:27:17 pm
content: Something is odd with your data signal.Why is the 0x07FF data serrated?And why is the data rising edge 1/2 cycle delayed?

author: Someone
author_rank: Super Contributor
timestamp: June 05, 2024, 10:29:12 pm
content: Quote from: dzseki on June 05, 2024, 10:07:40 pmThe data sheet is poorly written and doesn't explain the interface well. But, it does contain an example command string to set the wiper. Did you try using the example?

author: dzseki
author_rank: Frequent Contributor
timestamp: June 05, 2024, 10:32:26 pm
content: Quote from: Benta on June 05, 2024, 10:27:17 pmData must be present on the clock's falling edge. Serrations due o how the program was written is that a problem?

author: Benta
author_rank: Super Contributor
timestamp: June 05, 2024, 10:46:34 pm
content: I don't know.SPI is very simple and normally poses no problem. But as someone else wrote, the data sheet is lousy.And perhaps the program should be modified to be correct SPI?

author: ArdWar
author_rank: Frequent Contributor
timestamp: June 06, 2024, 12:17:05 am
content: Unusually sloppy datasheet from Analog indeed.Quote from: dzseki on June 05, 2024, 10:07:40 pmRead carefully the Write Protection section at page 20. The device will boot into internal preprogrammed value only by default. You need to clear the write protect bit to allow direct register control. Control bit is listed on table 11, and command formats are at table 12. Or if you're completely lost there's example initialization at table 15, you need to send0x1C03first.

author: dzseki
author_rank: Frequent Contributor
timestamp: June 06, 2024, 06:36:39 am
content: Quote from: ArdWar on June 06, 2024, 12:17:05 amIndeed, this did the trick! Now it works, thanks!