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Hi, with RPi 3 B+ there was no problem, upgraded to RPi 4B and the problem appears. I2C lcd shows unidentified characters after some layers or sometimes it shows blank and work fine again randomly. setup, wiring, power supply and everything are the same except RPi that is 4 instead 3. i should mention that there is no AC wire/Relay near lcd.
tested power supply used original RPi power supply for RPi4, upgrading/full upgrading RPi, replacing the lcd, nothing happened. going back to RPi 3, everything works well. is something wrong with RPi4?
here is the image:
https://img.techpowerup.org/200716/1949.png
Last edited by F.m (2020-07-16 19:15:48)
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Upgrade OS see if it does help or not
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as i said, i made full upgrade that means upgrading OS and firmware, it didn't help.
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i2c is very simple communication protocol. Nothing on nanodlp side could affect it. Also could not find any issue over net discussion difference on i2c between pi3 and pi4
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i posted in raspberry pi forum and some people said that it may be timing issue and referred me to the link below:
https://www.cpmspectrepi.uk/raspberry_p … gData.html
and here is my post in rpi forum:
https://www.raspberrypi.org/forums/view … 8&t=280320
how can i change lcd timing?
Last edited by F.m (2020-07-18 10:49:29)
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Dear Shahin, i suggest to read the thread here: https://www.raspberrypi.org/forums/view … 8&t=280320
1. someone suggests to use RPLCD library, may i know what library nanodlp using to drive character LCDs?
2. is it possible to change default library? if yes, what is the instruction?
3. can the baudrate (bus speed) makes this problem? i read some where to change the bus speed by doing: sudo modprobe -r i2c_bcm2708 and sudo modprobe i2c_bcm2708 baudrate=32000
Last edited by F.m (2020-07-20 20:34:25)
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the problem solved by using rpi 5v and ground pin, in order to prevent overloading the rpi, i used 5v and G of ramps which caused noise in lcd, now it works well.
but there still remains a question that, why it works in rpi3 B?
Last edited by F.m (2020-07-21 13:36:59)
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Power usage on pi 4 is higher than pi 3
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yes, it is. but i feel rpi4 is more sensitive to noises than rpi3.
they updated the firmware to reduce and manage power consumption recently.
Last edited by F.m (2020-07-23 09:15:12)
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