I am using the PRU to emulate an SPI bus and provide deterministic general-purpose digital lines. I am using:
I cannot find info concerning the output impedance of these lines and if there has been an attempt at the level of the BBB to match this output impedance with the impedance of the transmission lines by adding a series resistance. Does anyone know if:
- There are already series resistances on the expansion outputs of the board indented for impedance matching?
- The output impedance of the GPIOs from the AM335x
- If I should attempt impedance matching at the level at the cape level since there may be a fair bit of unmatched copper between my resistor and the GPIO pin on the AM335x.