What is Android Things Raspberry Pi GPIO max frequency?

Question

Where can be found the characteristics of the switching speed of GPIO port for the Raspberry Pi 3 under Android Things like that?

Answer 1

Here goes the results with C: it's near 100kHz.

Since I don't have a scope or proper equipment for these measures, here's what I did:

A java method that measures time, and invokes a C method that is efficient for a big number of cycles. This was for simplicity only, and I believe it's enough to show that for high number of cycles the speed asymptotically reaches almost 100kHz:

1 Iterations done in 501.38547 ms = 0.0019944734 kHz
10000 Iterations done in 599.4385 ms = 16.68228 kHz
100000 Iterations done in 1496.2832 ms = 66.83227 kHz
1000000 Iterations done in 10275.258 ms = 97.32116 kHz
2000000 Iterations done in 20104.879 ms = 99.47834 kHz

Among other things that the C code must do is sit waiting for 500ms until the pin is configured properly.

All code used for this measurement is available at https://github.com/fmatosqg/androidthings_ndk/tree/SO_speed_measurement, and I believe there still may be room for speed improvement. Though it uses a hack to write from C code, instructions available in the README.md.