PRU_ICSS vs PRU_ICSSG wrt GPIO and bi-directional communications

[DTJF]

I didn’t watch the video.

A floating line needs writing/reading registers in a GPIO-SS. This can be done by each cpu on the L3 bus (PRU, ARM, DSP, …).

Each GPIO-SS controls 32 lines. There’s one bit [0-31] for each line in the related read/write/data-out registers. So yes, some lines can float while others stay unchanged. You should take care that all lines are at the same GPIO-SS [0-3] (in order to control the paralel interface by a single register operation).

@Chris_Grey

I do expect to make relatively good use of the mailbox subsystem to pass Tx/Rx data-messages between the PRUs and the Processors. That traffic, I’m assuming would also be traversing the L3, and while it won’t be excessive, it will be present and thus adds some non-determinism to the system that will have to be tested for.

The rpmsg concept is not designed for real-time applications. Using UIO driver instead will speed up your development by making the timing in your application more predictable/reliable.

Regards