Upgrading from I2C (lenght=1m) to qwiic end to endpoint issue.

Qwiic System
1

Good afternoon,

Let me picture the situation first. A device running with a arduino mega build in to a electrical box has a display (JHD1313M1) connected with about 1m of cable in between. Now it’s possible that the display starts doing strange things and my guess the issue is the lenght of the cable that’s likely affected by surrounding voltages up to 400v.

I tried to fix that with 2 qwiicbus endpoint boards and followed “Alternate 2 - VCC2 at 3.8V to 36V” from this guide https://learn.sparkfun.com/tutorials/sp … okup-guide because I need 5V to power the display so 3.3V is not sufficient.

on the arduino side I connected the obvious wires: 3.3v, gnd, SDA and SLC to the arduino and next to that connected a external stable 5V (not supplied by the arduino) to VCC2 and it’s GND to GND2.

on the display side I connected the SCL and SDA + the VCC2 and GND2 to the display.

Yet somehow the display is not showing the right things and insteed showing black squares on the top rop and is blank on the bottom row

When measuring voltage on the Display side i got 5V on VCC2 powering the display and a 3.3V on the 3.3v pin supplying the qwiicboard. Next to that i checked continuity on the SDA and SCL pins as well.

So far I have no clue what i’m doing wrong here.

k6LOEP3.jpg1000×666 351 KB
https://i.imgur.com/k6LOEP3.jpg
0M5wjhC.jpg1000×666 349 KB
https://i.imgur.com/0M5wjhC.jpg

2

Are you saying the i2c lines are long or the ethernet side is 1m?

Can you test it with a very short ethernet cable, and/or away from the other EMF sources to rule that out?

3

Hi Russell

Thanks for the reply. Originally the i2c lines were about 1m long and we tried to replace them with the QWIIC end boards and a ethernet cable because we assumed having I2C wires running from the arduino all the way (1m) to the display was to sensitive and causing problems. Yet in the meantime the 30VAC to 12VDC Powersupply died (well it didn’t die but outputted almost 29VDC suddenly) and fried the arduino. We’re first fixing that with a more trusted supply and check in later again.

4

Did you connect the ground on the reciever board to the display as well (the one next to the SDA/SCL pins)?

/mike