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Part Number: DAC80508
Hi. I've been attempting to work with the DAC80508, as of yet to no success. I've got a few quick questions to hopefully find where I'm going wrong.
Thanks so much for your time, and sorry about the more vague nature of this post!
My colleague Uttam will be able to help you with this. For starters, can you also share the schematic? What are you using for the DAC reference?
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In reply to Paul_Frost:
Hi Paul, thanks so much! I'm just using the internal reference for the DAC, and when I measure it with my multimeter it's reading at a clean 2.5V. As for the schematic, I could throw something together, but it's hardly worth bothering. As of yet I'm just testing it before finalizing my circuit, so it's just wired directly to my microcontroller. Thanks!
In reply to Fraser Lee:
Thank you for your query. One quick question: are you using a 3.3V VDD or a 5V VDD. Note that there is a headroom requirement for the reference. With the internal 2.5V VVREF, we need to set the REFDIV bit in divide/2 configuration. For specific answers to your questions, please find my comments below:
Q1. Look at REFDIV and GAIN bits and set them appropriately. You can start with REFDIV=1 and GAIN=1
Q2. The CRC (enabled by the CRC-EN bit) is disabled by default
Q3. You can use SPI mode 1 (CPOL=0, CPHA=1) to start with.
Q4. The SPI implementation is mainly a shift register and hence, the minimum clock frequency won't matter
Q5. Please look at the above points and let me know if you are able to fix the problem
Applications Engineer, Precision DAC
In reply to Uttam Sahu:
Hi Uttam, thanks so much for the response! I've tried to test the device using loads of permutations on the settings you've suggested, and still am unable to get it to respond. My process is as follows:
After this the OUT0 pad still reads at 2.5V, the default value.
Among other things, I've also tried the following:
All to no avail.
Also to your question, I've been using 5V VDD through my circuit, so that shouldn't be an issue.
So my next question would be if there's any way to determine if this chip is even alive, or if it's possible this 2.5V behavior is just the last sign of life in an otherwise dead chip?
Thanks so much for helping me narrow down what this problem could be, and that it's not an issue with the voltage I'm using or the wrong SPI mode!
Hi again. So I've spent today attempting to get my debug Arduino to read something from the DAC's MISO, specifically when sending 0x81 0x00 0x00 through MOSI (which should trigger the dac to send me the contents of the device ID, including bits 6:2, reserved as 00101), and yet the MISO line remained low. Is there anything I can do to dispel my (increasingly more likely) concerns, that this thing is dead? I'd definitely try to test another unit if that were the case. This DAC really is perfect on paper, so I'd hate to try to look for an alternative, but I'm running out of time.
Thanks for all your help, and I'm so sorry to keep pestering you with questions about an almost certainly dead unit :)
I think at this point a few things will be needed to debug this:
1. A schematic - this can be a "back of the napkin" type drawing, but it is important to clarify that your setup is valid. It is a good exercise to go through, as usually, these issues breadboard systems are simple wiring problems.
2. You should verify your communication with a digital logic analyzer or oscilloscope. This is the fastest way to confirm if your SPI clock phase and polarity are correct.
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