Gpio/mux devkit help

[bardavid52]

Hi,

I’m looking to control a GPIO on the Orin AGX devkit, which is capable of driving around 20-30mA.

I’m on R36.4.3 and following the online manual I can configure the devkit’s pin7 using:
busybox devmem 0x02430070 w 0x004
and then:
gpioset gpiofind "PQ.06"=1
it all works - but pin7 is limited to 20uA.

According the carrier board specs, pin8 (UART1_TXD) and pin11 (UART1_RTS) are capable of driving 24mA.

I’m trying to control those pins, but it seems they stay high (3.3V), despite my attempts. Everytime I try to toggle them (whether 0->1 or 1->0), they drop to 0V for ~20us and then rise to 3.3V again - see capture below. I have no problem to control pin7, but interestingly, it seems its output voltage is ~2.3V and not 3.3V.

mux configuration:
robot@aziza:~/aziza$ sudo busybox devmem 0x024300A8 w 0x004
robot@aziza:~/aziza$ sudo busybox devmem 0x02430098 w 0x004
robot@aziza:~/aziza$ sudo busybox devmem 0x02430070 w 0x004
robot@aziza:~/aziza$ sudo busybox devmem 0x02430070
0x00000004
robot@aziza:~/aziza$ sudo busybox devmem 0x024300A8
0x00000004
robot@aziza:~/aziza$ sudo busybox devmem 0x02430098
0x00000004

switch all pins to zero:
robot@aziza:~/aziza$ gpioset gpiofind "PR.02"=0
robot@aziza:~/aziza$ gpioset gpiofind "PR.04"=0
robot@aziza:~/aziza$ gpioset gpiofind "PQ.06"=0

switch all pins to one:
robot@aziza:~/aziza$ gpioset gpiofind "PQ.06"=1
robot@aziza:~/aziza$ gpioset gpiofind "PR.04"=1
robot@aziza:~/aziza$ gpioset gpiofind "PR.02"=1

what am I doing wrong?

online docs:

Jetson AGX Orin Platform Adaptation and Bring-Up — NVIDIA Jetson Linux...

[KevinFFF]

Hi bardavid52,

@bardavid52

it seems its output voltage is ~2.3V and not 3.3V

Have you also used a scope(instead of logical analyzer) to check its signal?
Please check its pinmux register at this moment.

Have you applied the following patch before controlling GPIO in JP6.x?
40hdr - SPI1 gpio padctl register bit[10] effect by gpiod tools in JP6 - #20 by KevinFFF

[bardavid52]

Hi, yes, pin7 reaches ~2.2V when set to one, please see below:

pinmux register values:

robot@aziza:~/aziza$ sudo busybox devmem 0x02430070
0x00000054
robot@aziza:~/aziza$ sudo busybox devmem 0x02430070 w 0x004
robot@aziza:~/aziza$ sudo busybox devmem 0x02430070
0x00000004
robot@aziza:~/aziza$ gpioset gpiofind "PQ.06"=1
robot@aziza:~/aziza$ sudo busybox devmem 0x02430070
0x00000404
robot@aziza:~/aziza$ sudo busybox devmem 0x02430070
0x00000404

I have not applied any patch - I’m using a vanilla R36.4.3 as released by nvidia without any changes. is it needed to apply patches manually? thank you

[bardavid52]

I have noticed that when configuring pin8 pinmux:

robot@aziza:~/aziza$ sudo busybox devmem 0x024300A8
0x00000400
robot@aziza:~/aziza$ sudo busybox devmem 0x024300A8 w 0x004
robot@aziza:~/aziza$ sudo busybox devmem 0x024300A8
0x00000004

The pin starts low - on 0V.

Then after setting it to 1:

robot@aziza:~/aziza$ gpioset gpiofind "PR.02"=1

The pinmux register goes to 0x404:

robot@aziza:~/aziza$ sudo busybox devmem 0x024300A8
0x00000404

And at this point I can’t set it to 0 again.

If I try:

robot@aziza:~/aziza$ gpioset gpiofind "PR.02"=0

Then it goes to 0V, but jumps back to 3.3V after 40-50us (see attached).

But, interestingly, if i again set its pinmux register to 0x004:

robot@aziza:~/aziza$ sudo busybox devmem 0x024300A8 w 0x004
robot@aziza:~/aziza$ sudo busybox devmem 0x024300A8
0x00000004

Then it does go to 0 again.

[bardavid52]

Ok I found out the reason for the pin7 low voltage - it was my fault - it was connected to a FET which probably drew more current it could handle. Without it, I get ~3V (still not 3.3V, but maybe it’s reasonable):

So only problem left is why I can’t set back pin8 to 0V, without setting its pinmux register value again, and why its pinmux register value changes to 0x404 after I use gpioset to set it to 1.

[bardavid52]

ok read the thread with the patch, it sounds like this is the solution, thank you