How to enable PWM in Ubuntu Server 18.04 Image

#1

I followed the instructions available here: https://wiki.radxa.com/Rockpi4/hardware/devtree_overlays.

I Installed rockchip-fstab and rockpi4-dtbo, edited /boot/hw_intfc.conf to set pwm0 and pwm1 to on, but after a reboot I am still getting that device is busy.

root@rockpi:/sys/class/pwm/pwmchip0# cat npwm 
1
root@rockpi:/sys/class/pwm/pwmchip0# echo 0 > export
-bash: echo: write error: Device or resource busy
root@rockpi:/sys/class/pwm/pwmchip0# echo 1 > export
-bash: echo: write error: No such device

I believe /boot/hw_intfc.conf is being ignored. Is there anywhere else that could set this?

My image is Ubuntu Server 18.04

Possible to use 5V Relay module with GPIO?
#2

Hi rodvlopes,

Can you provide the print of df?

#3

And the print of ls -l /sys/class/pwm

#4 
root@rockpi:/sys/class/gpio/gpio146# df
Filesystem     1K-blocks      Used Available Use% Mounted on
/dev/root       14722052   4297868   9785880  31% /
devtmpfs          985872         0    985872   0% /dev
tmpfs             986480         0    986480   0% /dev/shm
tmpfs             986480      2500    983980   1% /run
tmpfs               5120         0      5120   0% /run/lock
tmpfs             986480         0    986480   0% /sys/fs/cgroup
/dev/mmcblk1p4    102182     38844     63338  39% /boot
/dev/sda2      858090292 438977276 375501436  54% /mnt/sda2
tmpfs             197296         0    197296   0% /run/user/0

root@rockpi:/sys/class/gpio/gpio146# ls -l /sys/class/pwm
total 0
lrwxrwxrwx 1 root root 0 Jan 28  2018 pwmchip0 -> ../../devices/platform/ff420020.pwm/pwm/pwmchip0
#5

Please execute the following command and let me know the result

cat /boot/hw_intfc.conf
sudo umount /boot
ls -al /boot
cat /boot/hw_intfc.conf

#6 
root@rockpi:~/workspace/scripts# cat /boot/hw_intfc.conf                                                                                               [27/29]
                        
# Hardware Interface Config
                                                            
# For more details, check https://wiki.radxa.com/Rockpi4/hardware/devtree_overlays.

# Set "on" to enable the optional hardware interfaces while set "off" to disable.
                          
intfc:pwm0=on
intfc:pwm1=on                                                                  
intfc:uart2=off               
intfc:uart4=off
intfc:spi1=on                                                                  
intfc:spi2=off                       
intfc:i2c2=off
intfc:i2c6=off                                                              
intfc:i2c7=off                    

# Devicetree Overlay Enable, uncomment to enable .dtbo under /boot/overlays/.
                          
# EEPROM on I2C2
#intfc:dtoverlay=at24c02
                              
# Serial console on UART2
intfc:dtoverlay=console-on-ttyS2                   
                                  
# Serial console on UART4
#intfc:dtoverlay=console-on-ttyS4               
                                       
# Dummy spi device on SPI1 for test. Need set: intfc:spi1=on
#intfc:dtoverlay=devspi1         
                        
# Dummy spi device on SPI2 for test. Need set: intfc:spi2=on
#intfc:dtoverlay=devspi2                                               
                       
# PCIE running on GEN2 mode
#intfc:dtoverlay=pcie-gen2                                             
                       
# ALLNET 4duino B10/B11 two-coloe-led module on 40-pin Header Pin#35 and Pin#36
#intfc:dtoverlay=two-color-led                          
                            
# waveshare 3.5inch lcd (B v2) on SPI1. Need set: intfc:uart4=off intfc:spi1=on
#intfc:dtoverlay=spi1-waveshare35b-v2

# waveshare 3.5inch lcd (C) on SPI1. Need set: intfc:uart4=off intfc:spi1=on
#intfc:dtoverlay=spi1-waveshare35c

# spi flash on SPI1. Need set: intfc:uart4=off intfc:spi1=on
intfc:dtoverlay=spi1-flash

#hifiberry-dac
#intfc:dtoverlay=hifiberry-dac

#hifiberry-dacplus on I2C7. Need set: intfc:i2c7=on
#intfc:dtoverlay=hifiberry-dacplus

#enable raspberry pi official 7 inch LCD support
#intfc:dtoverlay=raspberrypi-7-inch-lcd

# setting cpu frequency over-2GHz
#intfc:dtoverlay=cpufreq

# Add imx219 camera module support. Need disabled ov5647 camera module.
#intfc:dtoverlay=imx219

# Add ov5647 camera module support. Need disabled imx219 camera module.
#intfc:dtoverlay=ov5647

# Add w1 on GPIO4_D6 to support devices such as DS18B20.
#intfc:dtoverlay=w1-gpio4-30

–

root@rockpi:~/workspace/scripts# umount /boot
root@rockpi:~/workspace/scripts# ls -al /boot
total 8
drwxr-xr-x  2 root root 4096 Apr 24  2018 .
drwxr-xr-x 23 root root 4096 Jan 28  2018 ..
root@rockpi:~/workspace/scripts#

–

root@rockpi:~/workspace/scripts# cat /boot/hw_intfc.conf
cat: /boot/hw_intfc.conf: No such file or directory
root@rockpi:~/workspace/scripts#
#7

Sorry for the late reply. You can try updating the kernel via:

sudo apt-get install linux-base
sudo apt-get install linux-4.4-latest

#8

I dont have linux-4.4-latest yet but my kernel is exactly in this version. I will prepared a new SD card to test this change to avoid messing up my running server.

root@rockpi:~# dpkg --get-selections | grep linux-4.4-latest
root@rockpi:~# dpkg --get-selections | grep  linux-base
linux-base					install
root@rockpi:~# uname -a
Linux rockpi.localdomain 4.4.154-59-rockchip-g5e70f14 #4 SMP Fri Dec 14 20:55:41 CST 2018 aarch64 aarch64 aarch64 GNU/Linux
#9

You can use rockpi-backup.sh to back up your system.