@thomas166 So there few components to your requirements. The first is that you don't want to have the firmware misimatch issue. The only solution to that is you need to that is to create a DTS for the lte, since sysupgrade reads the device type from from /tmp/bard.json and /etc/board.json, these are created when the device tree is loaded, so you need to create a dts with the correct identifier in it. Here is a link to a patch I created that will add the lte device and include the lte-base in the build. This is a patch for OpenWrt 23.05.3 so you may have to merge it in manually.

PWM is very interesting to me because how it reminds me of AC.

@Chris-McCaslin Try using any pins other than 20 and 21 since they run the I2C protocol. With regards to the servo, while fast-gpio is pretty handy, it's still software-based PWM. Anytime another process gets the CPU's full attention, the PWM signal will change. This will happen many times a second, so the PWM signal going to the servo will be constantly changing. This change in the PWM signal is the reason why your servo is twitching. Sorry, but your best bet for a non-twitchy servo is the Servo Expansion. Another thing, your servo accepts a high pulse of 1ms to 2ms in a 20ms PWM period. For the farthest position in one direction you would send a signal that is 1ms high and 19ms low, meaning a 5% duty cycle The farthest position in the other direction requires a signal that is 2ms high and 18ms low, so a 10% duty cycle And the neutral position would be: 1.5ms high and 18.5ms low, so 7.5% duty cycle

@Brian-Piersel No problem. Glad it helped.

@Boken-Lin Thank you!

Andrei - I don't know if this helps, but your comments were so helpful I wanted to mention this. I've had ruby installed and didn't see a lot of additional dependencies. I just now installed ruby-irb and saw that opkg installed a whole bunch of ruby-related stuff. opkg install ruby-irb Installing ruby-irb (2.2.4-1) to root... Downloading http://downloads.openwrt.org/chaos_calmer/15.05.1/ar71xx/generic/packages/packages/ruby-irb_2.2.4-1_ar71xx.ipk. Installing ruby-debuglib (2.2.4-1) to root... Downloading http://downloads.openwrt.org/chaos_calmer/15.05.1/ar71xx/generic/packages/packages/ruby-debuglib_2.2.4-1_ar71xx.ipk. Installing ruby-multithread (2.2.4-1) to root... Downloading http://downloads.openwrt.org/chaos_calmer/15.05.1/ar71xx/generic/packages/packages/ruby-multithread_2.2.4-1_ar71xx.ipk. Installing ruby-misc (2.2.4-1) to root... Downloading http://downloads.openwrt.org/chaos_calmer/15.05.1/ar71xx/generic/packages/packages/ruby-misc_2.2.4-1_ar71xx.ipk. Installing ruby-prettyprint (2.2.4-1) to root... Downloading http://downloads.openwrt.org/chaos_calmer/15.05.1/ar71xx/generic/packages/packages/ruby-prettyprint_2.2.4-1_ar71xx.ipk. Installing ruby-filelib (2.2.4-1) to root... Downloading http://downloads.openwrt.org/chaos_calmer/15.05.1/ar71xx/generic/packages/packages/ruby-filelib_2.2.4-1_ar71xx.ipk. Installing ruby-enc (2.2.4-1) to root... Downloading http://downloads.openwrt.org/chaos_calmer/15.05.1/ar71xx/generic/packages/packages/ruby-enc_2.2.4-1_ar71xx.ipk. Installing ruby-math (2.2.4-1) to root... Downloading http://downloads.openwrt.org/chaos_calmer/15.05.1/ar71xx/generic/packages/packages/ruby-math_2.2.4-1_ar71xx.ipk. Installing ruby-patterns (2.2.4-1) to root... Downloading http://downloads.openwrt.org/chaos_calmer/15.05.1/ar71xx/generic/packages/packages/ruby-patterns_2.2.4-1_ar71xx.ipk. Configuring ruby-enc. Configuring ruby-misc. Configuring ruby-filelib. Configuring ruby-multithread. Configuring ruby-patterns. Configuring ruby-math. Configuring ruby-prettyprint. Configuring ruby-debuglib. Configuring ruby-irb.