Is it possible to set P9_42 as pruout?

General Discussion
1

I want to measure a high-speed square wave signal with an oscilloscope.

1 MHz or more.

For that reason, I try to pick an output pin as close to the ground as possible.

Is it possible to set P9_42 or P9_41 as pruout?

$ config-pin -l P9_42

output doesn’t list pruout in available modes.

I was thinking about using a small metal spring to measure and keeping the measurement distance short.

I use Beaglebone white.

2

Both those pins are extra special, should be a P9_42a, P9_42b… or P9_92, depending on device tree…

3

I think there is only P9_92 available.

$ config-pin P9_92 pruout

Current mode for P9_92 is:     pruout

Does that mean P9_92 and P9_42 are same?

I have a small C program which blink the LEDs.

If I set P9_92 as pruout nothing happens.

If I set P9_31 as pruout it works as expected.

4

Correct, while both are “P9_42” one is the first set of pins, the other the other set of pins… (it’s 2 pins connected to one pin)…

Did you set the other P9_42 to input?

Regards,

5

How should I set the other P9_42 to input?

$ config-pin -l P9_42

Available modes for P9_42 are: default gpio gpio_pu gpio_pd spi_cs spi_sclk uart pwm pru_ecap_pwm
6

gpio mode is fine.

7

Let me summarize what I’ve done so far.

I set P9_42 as gpio.

config-pin P9_42 gpio

I set P9_92 as pruot.

config-pin P9_92 pruout

However, nothing happens.

The definition of pin 42 in the source file is as follows.

#define P9_42 (1 << 4)

If P8_12 is set to pruout, it works properly.

However, it is physically challenging to measure. Due to the probe’s short ground spring.

This signal was measured using the alligator clip that came with the probe.

This is a 1 MHz square wave.

As the square wave rises and falls, there are oscillations and ringing.

I try to make some tests to make sure that the scope works correctly.