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A bit of a context-specific question, but maybe pe...
# mpw-6plus-silicon
x
A bit of a context-specific question, but maybe people here have experience with this: Is it possible that the mprj_io[5:1] pins work (in that they can be controlled as outputs from the management core), but cannot be used to get the project ID?
We have a bare die that we have packaged ourselves and trying to test to see if our interconnects work. Running any of the firmware functions fails since it cannot get a project ID from our package. However, I was able to get around this problem by plugging in a working QFN and flashing firmware onto the PCB memory then plugging in our assembly and using the PCB flash memory to program the bare die. I used the "blink" firmware to blink all 38 of the GPIO pins and used a multimeter on our PCB to look for pins which were not blinking at the given frequency. I found three pins which did not blink, but these were not the mprj_io[5:1] pins, which I believe are the ones talking to the FTDI.
t
Which shuttle run was the chip you're testing fabricated on?
x
This is a MPW7 baredie
t
There shouldn't be any issue with getting the project ID. What specifically is the problem?
x
image.png
t
Which project is that?
x
(this project ID command worked for the MPW-7 QFN parts that we had received and also works for our 2206Q parts as well)
t
Do you get a different output from 
caravel_projectid.py
if you hold the reset button down while you're running it?
x
When I tried that, sometimes it'd return all 0s
but other times it'd be the same
t
Oh, so the problem is specific to the bare die part? Did you get it wirebonded or are you testing it some other way?
x
We have it flip chipped bonded to a silicon substrate then wire bonded to an interfacing PCB
Yes it seems to be specific to this assembly
I could try to get the project ID from 1 that we have wire-bonded to see if the issue occurs with other bare die
t
I'm trying to think of a way that GPIO 1-4 could produce a working output for the blink test yet fail to produce an output when communicating with the SPI. I'm not coming up with anything.
x
Yea... it's a bit of a strange problem; I will try to track down if there any routing mistakes with any of our parts...
t
The only thing I can think of is an incorrect connection between GPIO 1 to 4 and the FTDI. You're getting full chip functionality, just not any communication through the FTDI.
x
I see, will double check the nets on all of our parts. Thanks for the quick chat Tim!
following up on this, found a mixup in one of the SPI nets and was able to successfully talk to the chip over USB after fixing our PCB
🙌 1
t
Great!
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