Author Topic: How to determine spi pins?  (Read 616 times)

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Offline sirtet

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How to determine spi pins?
« on: January 28, 2018, 10:56:20 pm »
So, I have this Bluetooth module with a piggyback pcb on it, and on that pcb is an soc (csr8645), that has an spi port, but I can't tell if the spi pins are on the pcb, cause it's a bga chip.
There are 4 pins on the piggyback pcb (pins 12-15) that i guess are the spi ones, because
they go to test points on the main pcb bottom side.
But how to tell which is which?

Is there a  better approach to figure them out than trying lots of combinations,
Sending a command and probing for an answer?
 

Offline bitwelder

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Re: How to determine spi pins?
« Reply #1 on: January 30, 2018, 12:40:22 pm »
step 1. Plug a logic analyzer (or an oscilloscope that can also decode SPI) and observe?
step 2. Make guesses on the pins function and try to decode valid SPI messages?
 


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