ADAU1452 based custom board, unable to read registers
Hello everyone,
I designed a PCB based on the ADAU1452 DSP, where the relevant parts in terms of my question are basically copy-pasted from the EVAL board of this DSP. Only the layout is different.
When I was trying to upload a simple program (LED blink) to the DSP it didn't work, but the same program worked on the EVAL board. So after that, I tried to see if any data from the registers can be accesed through the programmer (I use SigmaStudio and the programmer given for the EVAL board), but I got no data (0xFF, 0xFF).
The power should be alright, the board takes 7.4mA, the 1.2V regulator works (I can measure 1.2V on the transistor's drain). I checked a number of times if my programmer connector layout is correct, and yes, it should be correct.
May I ask your help in this regard? Have I made a mistake on the schematic? Or the PCB layout is that bad that it is unable to be programmed? Or what is what I don't see? I was trying to check if there is any short connection on the path of the SPI line, but didn't find any. Also, I tried to check if there is any soldering error around the DSP, but again, didn't fin anything. Is there another voltage I could measure somewhere which would tell me wheter the DSP works or not? My guess is that having the 1.2V is a good sign.
I attach a picture of the relevant part of my schematic and PCB layout. Also you can find it on this link https://ibb.co/yRNTqz8
Thank you in advance!
Bálint
Audio Signal Processors
adau1452
SigmaDSP Audio Processors
Hello again,
I am still trying to figure this out. There was one problem most certainly: a pull-down resistor was missing from the /SS line. Also, I did a reflow, so now I read 0x00 instead of 0xFF or 0x7F.
After the above, I measured with an oscilloscope the MISO/MOSI lines to see if there is any noise or whatever which would prevent the right communication.
Here, it turned out that the voltages are not right. The MOSI was correct, I see the signal when I read for example the registers, but the answer back on the MISO line doesn't seem right.
The base voltage on MISO for example not GND but a bit above that, around 50mV-100mV, also when it tries to answer back to the master, the high signal is really low, around 200mV. The MISO signal's square wave can be seen on the scope screen, so my guess is that the DSP understands the register read request, but it cannot open the push-pull's high-side transistor, or it can, just the voltage there is not right.
I was checking all the power supply inputs if the soldering is right, and I am quite confident that they are good.
My question here: Which power supply goes to this part of the DSP? I could resolder it again or at least focus on that the most, so maybe I could solve this problem this way.
Also, can it be that I miss something on the board which is important from the programmer's perspective? Something which is trying to pull-down the signal perhaps?
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