That really helped. During boot I was also seeing the yellow “undervoltage flash” now Also continued after boot but don’t see any undervoltage warnings. in live log.
Screen flashes multiple times all white during starup and chromium starts after statup. Finaly a page is loaded, but not the HMI instead it reaches "This site can’t be reached localhost refused to connect.
Last messages in live log is:
Stopping cpufrequtils.service - LSB: set CPUFreq kernel parameters…
glamor-test.service: Deactivated successfully.
Stopped glamor-test.service - Check for glamor.
ERR: ntpd exiting on signal 15 (Terminated)
Stopping ifplugd.service - LSB: Brings up/down network automatically…
PROTO: 192.121.108.100 unlink local addr 192.168.1.76 →
PROTO: 194.58.207.148 unlink local addr 192.168.1.76 →
PROTO: 162.159.200.1 unlink local addr 192.168.1.76 →
PROTO: 192.36.143.134 unlink local addr 192.168.1.76 →
PROTO: 194.58.200.20 unlink local addr 192.168.1.76 →
PROTO: 162.159.200.123 unlink local addr 192.168.1.76 →
PROTO: 193.182.111.13 unlink local addr 192.168.1.76 →
edit: sorry I was to prompt in my reply. After some minute I now see the correct screen! Big progress. Touchscreen doesn’t work and the yellow flash in top right corner is constant.
That is real progress - the display working confirms the KMS driver was the problem for this display. Without it, the firmware framebuffer persists at your configured resolution and Xorg runs on fbdev without conflict.
Three things to deal with now. We can do two of them in one step.
Touch - expected, fixable now
The ADS7846 overlay is commented out in your userconfig.txt so the touch controller is not being initialised. Your display uses a Waveshare-compatible ADS7846 SPI touch controller which needs a specific overlay.
Make sure the old line stays commented out or is removed entirely. dtparam=spi=on should remain as it is. Save and exit.
Undervoltage - the constant yellow flash
The lightning bolt in the top right corner means the Pi is detecting undervoltage right now, even after the M SCALER power fix. What is the current state - is the M SCALER powered from mains, or disconnected? Is anything else different from when the Y9nG4Em log showed only 1 undervoltage event?
Logs
After making the touch changes above, reboot and test:
I haven’t done anything with the M SCALER, it has been connected and powered up all day.
Previosly I’ve seen the ligtning bolt lit up together with flash of the red LED of the raspberry pi. Now it seems like the flash bolt is inverted, it is lit all the time but turns off when the red LED flashes. I didn’t see any red LED flash at all during last boot but saw, or maybe looked closer after it now after touch reboot. Didn’t saw any undervoltage warnings in Live log previously
I disconnected and reconnected the USB cable to M-scaler after boot. Not sure if it helped anything.
edit:
After measuring output voltage from power supply I can see this seems to be stable at 5V but instead measuring output power from the USB ports of the raspberry pi I can see it is below 4,8V and also saw a measurement of as low as 4.65V, just with a very simple usb power meter. so most probably dips much lower than this.
At the same time the current keeps at maximum around 1A. My impression was that this USB cables were quite good quality, solid connectors with a nice snap. But has to be to little copper area, even if it is just 1m long. I need to search for some better cables. Adding one cable at the display and one at the pi itself solves the problem with the yellow flash bolt.
Display and touch are both working. The log confirms it.
Summary of what was done and why
KMS driver disabled in videoconfig.txt
Your display is a small HDMI panel (Waveshare-compatible clone) that uses a custom firmware mode (1024x600 via hdmi_cvt) not present in the display’s EDID. When the KMS driver (vc4-kms-v3d) loaded, it read the EDID, found no matching mode, and the display went dark. On top of that, Xorg then crashed because two video drivers (fbdev and modesetting) were both trying to claim the hardware simultaneously.
With KMS disabled, the firmware framebuffer persists through the entire boot at the resolution the firmware configured. Xorg runs on fbdev without conflict. This is the same approach Volumio uses for the Pi Zero 2 W.
Legacy HDMI parameters removed from userconfig.txt
These were conflicting with pi_screen_setup’s managed configuration in videoconfig.txt. Removing them allowed the plugin to manage display settings without interference.
Waveshare ADS7846 touch overlay installed
The waveshare-ads7846 overlay was downloaded to /boot/overlays/ and enabled in userconfig.txt. The kernel now initialises the SPI touch controller correctly.
Undervoltage identified as cable problem
The Chord Hugo M SCALER was drawing parasitic current through USB when its own power was disconnected from mains - resolved by keeping the M SCALER powered. The remaining undervoltage is caused by the Remax Full Speed cable - your own measurements confirm 5V at the supply dropping to 4.65V at the Pi’s USB ports under just 1A load. That is a 0.35V drop across 1 metre of cable, which indicates insufficient copper cross-section for sustained power delivery.
You need a cable rated for power delivery, not a data cable. Look for cables advertised as 20AWG or lower (lower AWG number means thicker copper). Many micro USB cables sold as “charging cables” use 28AWG wire which cannot sustain the current a Pi 3B+ with peripherals requires.
Thanks a lot for all the help during the weekend! Really helped and also make me understand the mechanism behind!
What’s still strange is that I didn’t saw any low voltage warnings after I disabled touch overlay in the userconfig.txt. I’ll try to comment out this line and see if the undervoltage warning disappears, more of curiosity, I’ll replace the cable anyway.
Next step would be to update my Volumio Primo (old one) to Volumio 4. I don’t use this as it is now, it gives, and have more or less always give glitches in the playback. With volumio 4 on all other nodes it is neither not possible to use the old Primo for multiroom playback. Is there some way to load Volumio 4 to Volumio primo? Open it up and load the pre compiled Tinkerboard version trough the micro USB port? Will it give a mess with OTA updates etc?
Thanks for the reply. I know there are no official releases, but I thought there might be possible to just load the tinkerboard version of Volumio 4 or maybe there was a beta release to evaluate. Better test with a buggy beta than not using it at all as it is right now… But believe I’ll wait some more time then.