Recently I'm trying to use my rpi4B as a in-situ SPI flash programmer. Although it works alright most of the time, there are some issues about data line idle state that I'd like to see if they can be fixed.
I found that the idle state of SPI lines differs from product to product, especially for MOSI, MISO and CLK lines.
For example, one of the products I'm testing have all three lines pulled to HIGH when the processor is not accessing the flash chip, another one has only MOSI and MISO pulled to HIGH.
As for the pi, all SPI pins except CS are LOW when not in use.
This makes the SPI lines idle in a weird middle state when I connect a LOW rpi pin to a HIGH target pin. Although it seems my rpi can still manage to read correct data with lower clock speed, I still want to see if I can eliminate the uncertainty introduced by the middle state voltage.
My thoughts for now is to first check the idle state of target SPI line, then set my rpi's SPI line to the exact same. But it seems there are no easy way to define the default state of the SPI line on an rpi.
I tried to use but it doesn't work on SPI1 pins (GPIO20 and 21).
Any advice is appreciated!
I found that the idle state of SPI lines differs from product to product, especially for MOSI, MISO and CLK lines.
For example, one of the products I'm testing have all three lines pulled to HIGH when the processor is not accessing the flash chip, another one has only MOSI and MISO pulled to HIGH.
As for the pi, all SPI pins except CS are LOW when not in use.
This makes the SPI lines idle in a weird middle state when I connect a LOW rpi pin to a HIGH target pin. Although it seems my rpi can still manage to read correct data with lower clock speed, I still want to see if I can eliminate the uncertainty introduced by the middle state voltage.
My thoughts for now is to first check the idle state of target SPI line, then set my rpi's SPI line to the exact same. But it seems there are no easy way to define the default state of the SPI line on an rpi.
I tried to use
Code:
raspi-gpio set X puAny advice is appreciated!
Statistics: Posted by JensPi — Thu May 30, 2024 6:02 am