I have found that an off the shelf Nakto M5 display without Aventon firmware works just fine! The display isn't terminated to the Higo/Julet 5 pin male connector, but I can remove the back cover + wires of the old display and solder those onto the new one, or I can splice on the extension cable I bought.
Turns out the controllers used here are using Kingmeter 618U / J-LCD protocol. I verified this by hooking up the new and broken old display to a logic analyzer and found the protocols to match this library
https://github.com/MichaelFabry/Ard...uino_Pedelec_Controller/display_kingmeter.cpp
The APT TFT 750C does not work and I do not know what I will do with this. I may try to reverse engineer it, following the 850C board's custom firmware, and add this protocol in. The protocol is simple but reversing the board is not!
The new display has many more settings, see
https://www.e-bikes.com/pages/nakto-ebikes-lcd-control-panel-instruction
Mine is configured as follows:
P01 - 2
P02 - 1
P03 - 48V
P04 - 10
P05 - 1
P06 - 4
P07 - 16
P08 - 40
P09 - 1
P10 - 2
P11 - 1
P12 - 1
P13 - 12
P14 - 15
P15 - 41.0
P16 - N/A
P17 - 0
P18 - 100
P19 - 1
P20 - 2
I messed around with P05 and found out that some of the higher level PAS settings (This display went alphanumeric on me!) just made the bike drive itself forward, way faster than the walk mode!
P06 is normally in inches, but in this instance it maps to the default tire settings available. Follow the order in your Aventon user manual from smallest to largest, number 4 is 24". The 618U protocol has the display state wheel size every packet, I confirmed these map between displays. The kingmeter library above also shows this order.
I'm uncertain if P07 is actually 16, I need to do some real world testing, but this setting doesn't leave the display and Shengyi doesn't list this specific model online. However, their similar models all have 16 pole pairs, so I believe this is correct.
P11 is essentially number of magnet counts before PAS kicks in. I haven't done any real world testing, but I didn't notice any difference here. Messages in this protocol are only sent every 1/2 second, so that doesn't really buy you much anyway.
P12 keeps PAS from kicking in strongly, it's nice to be able to set this depending on ride.
P14 makes no difference here! The controller we have internally limits to 22A. The display does not echo this setting back to the controller, I did not see any changes in the packets. The controller also does not report current to the display, this field was always 0. I set this to 1A and noticed no difference.
P15 is to match the controller.
P17 enabled would allow you to have the motor cruise you at speed without pedaling. I don't care for this style.
P18 would be used as a ratio if your tire sizes don't line up to the available ones.
P19 lets PAS 0 be selected.
P20 is usually listed as "Alternate" or "Standby" in product listings for this screen and others with the same style settings where P20 decides protocol. I think this display is a Kingmeter Nokee-U knock-off, so it would make sense to not broadcast the name of the protocol.
All in all, the display in our system is really only displaying speed and turning off PAS if you're up to speed. Lameeeeeeeeee.