Another PWM issue

Autonomous Machines Jetson & Embedded Systems Jetson TK1
1

I have recompiled Grinch 21.3.4 with modified tegra124-jetson_tk1-gpio-pm375-0000-c00-00.dtsi and tegra124-jetson_tk1-pinmux-pm375-0000-c00-00.dtsi as it is discribed here - Jetson/PWM - eLinux.org. I’m trying to get something out of PWM0 under root:

echo 0 > /sys/class/pwm/pwmchip0/export
echo 10000000 > /sys/class/pwm/pwmchip0/pwm0/period
echo 5000000 > /sys/class/pwm/pwmchip0/pwm0/duty_cycle
echo 1 > /sys/class/pwm/pwmchip0/pwm0/enable

but I get nothing out of gpio163 (pin 49 on J3A2). What I’m doing wrong?

2

Unfortunately the web link above shows an empty page, so I’m not sure what it described when you saw it.

Just as a checklist though, the compile should produce a “.dtb” version in kernel directory “arch/arm/boot/dts/” (tegra124-jetson_tk1-pm375-000-c00-00.dtb). I would then place a copy with a modified name in /boot, e.g., tegra124-jetson_tk1-pm375-000-c00-00_pwm.dtb, and name this in an alternate boot entry to /boot/extlinux/extlinux.conf. Have you placed the compiled alternate “.dtb” file in /boot and have you named it as the new FDT firmware file? If not, the firmware changes would not show up.

3

Dot at the end is part of punctuation not part of a link. Jetson/PWM - eLinux.org .

I followed your instructions and this not help me either. Still nothing at the output of gpio163 (pin 49 on J3A2).

4

I don’t know if this is the issue, but I did notice a difference between what is on the wiki page versus the commands you posted here.

echo 10000000 > /sys/class/pwm/pwmchip0/pwm0/period
echo 1000000 > period

echo 5000000 > /sys/class/pwm/pwmchip0/pwm0/duty_cycle
echo 500000 > duty_cycle

Both of the numbers are off by a factor of 10.