Strange behaviour of the bpi r3 mini

Banana Pi Router design BPI-R3/R3 Mini(MT7986)
1

Hi All, i observed some strange things in the banana pi r3 mini. Just want to tell about and maybe some other also know about that and can give a comment.

Starting point was a new banana pi r3 mini. I confess, I’m lazy, because i didn’t want to play with that small pins at first and I tried to connect the usb-c to usb-c connection first and there was nothing - so ok I get my magnifier, turn on the lights and used the shipped ch340 and connected the pins with the cable and, whoohoo, there’s serial output. Both emmc and nand were booting fine but there was an old openwrt release.

After playing around to get to know the system with several reboots, change boot switch, check network funtionality, etc., I noticed that the serial stop working - no output at all anymore - not in putty, not in mobaxterm, not in minicom in linux - nowhere - nothing. Ok, it was late evening, I continue the next day. On the next morning power on laptop, power on r3 mini, open putty and the serial output was back - wtf ???

Later that day, serial was of again like before. Hmm strange but ok and nand and emmc are still fine. Maybe a problem with that ch340. (yes no change on the cable connecting the pins) When booting or key press the blue led of the ch340 is flashing but not output in the terminal. Connecting the rx-tx on the ch340 with a jumper for testing, gives me a normal output of the pressed keys. So that ch340 seems to be ok.

Then I remembered my first attempt usb-c to usb-c connection. (When using the shipped ch340 before, the r3 mini was always connected with its own power supply.) So I connected the usb-c from the r3 mini with the usb-c from my laptop - the device manager gives me now a additional ch340 port (that wasn’t there at the first attempt) and the mobaxterm gives me an output. So, why the serial output changes to the usb-c without any changes from my side and without any visible reason? And, how to go back to the original settings??? And when is the next change??? And what might be that change???

Ok, so many questions. Time for something else… (I like when there are many riddles)

So lets boot to nand and upgrade the emmc to openwrt-24.10.0-rc5-mediatek-filogic-bananapi_bpi-r3-mini-emmc-… Because I have a quectel rm520n connected in the m.2 slot, that was not recognised by that original openwrt (21.02…)

after some flashing, time to boot the new openwrt from the emmc and there it is, a new openwrt. the serial is still on the usb-c, so everything’s fine.

Nooo, of course not.

  • no quectel rm520, but maybe there’s something missing…
  • and more bad the nand is not booting anymore - wtf?

When booting the nand, this is the output and the fan tries a new world record in rotation speed: P#▒B▒c▒BCB▒cC▒Bm!# BG▒#(▒▒▒E

These were steps to flash the emmc (the file were copied before from external usb drive to /tmp):

  1. dd if=/tmp/openwrt-24.10.0-rc5-mediatek-filogic-bananapi_bpi-r3-mini-emmc-gpt.bin of=/dev/mmcblk0
  2. Reboot
  3. echo 0 > /sys/block/mmcblk0boot0/force_ro dd if=/tmp/openwrt-24.10.0-rc5-mediatek-filogic-bananapi_bpi-r3-mini-emmc-preloader.bin of=/dev/mmcblk0boot0 dd if=/tmp/openwrt-24.10.0-rc5-mediatek-filogic-bananapi_bpi-r3-mini-emmc-bl31-uboot.fip of=/dev/mmcblk0p3 dd if=/tmp/openwrt-24.10.0-rc5-mediatek-filogic-bananapi_bpi-r3-mini-initramfs-recovery.itb of=/dev/mmcblk0p4 dd if=/tmp/openwrt-24.10.0-rc5-mediatek-filogic-bananapi_bpi-r3-mini-squashfs-sysupgrade.itb of=/dev/mmcblk0p5 sync
  4. unplug power cord, change switch back to emmc

So the emmc is fine, but is it a good idea to try some flashing of the nand or how to bring the nand back to life???

Thanks for reading :slight_smile:

(English is not my native language.)

2

Starting point was a new banana pi r3 mini. I confess, I’m lazy, because i didn’t want to play with that small pins at first and I tried to connect the usb-c to usb-c connection first and there was nothing - so ok I get my magnifier, turn on the lights and used the shipped ch340 and connected the pins with the cable and, whoohoo, there’s serial output. Both emmc and nand were booting fine but there was an old openwrt release.

Well, there is something definitely wrong if your USB-C serial has no output. I think this is the case, where your cable is bad and your laptop/PC cannot power the R3 mini properly. Did you changed power source when you tried the ch340?

After playing around to get to know the system with several reboots, change boot switch, check network funtionality, etc., I noticed that the serial stop working - no output at all anymore - not in putty, not in mobaxterm, not in minicom in linux - nowhere - nothing. Ok, it was late evening, I continue the next day. On the next morning power on laptop, power on r3 mini, open putty and the serial output was back - wtf ???

Do you have fan and case for the R3 Mini or just the PCB? Because this still the expected behavior with bad quality cable/power source. At the beginning, I used my USB-C cable from my phone and tablet, it didnt worked. Then I got a more expensive, quality cable and with that I can power the R3 mini from my notebook for hours without issues with fully spinnig fan.

Then I remembered my first attempt usb-c to usb-c connection. (When using the shipped ch340 before, the r3 mini was always connected with its own power supply.) So I connected the usb-c from the r3 mini with the usb-c from my laptop - the device manager gives me now a additional ch340 port (that wasn’t there at the first attempt) and the mobaxterm gives me an output. So, why the serial output changes to the usb-c without any changes from my side and without any visible reason? And, how to go back to the original settings??? And when is the next change??? And what might be that change???

I have the following theory:

  1. Power supply + ch340: works as expected, the power adapter does not recognized as a serial device, therefore the serial output of R3 remains the pins
  2. Laptop power + ch340: no output on ch340, probably if USB-C recognized as a serial, the output defaults to that one
  3. Laptop power + USB-C + ch340: the output should be the USB-C serial, but maybe the cable quality is bad and sometimes only recognized as power, and the output switch to the ch340 then back.
3

Well, there is something definitely wrong if your USB-C serial has no output. I think this is the case, where your cable is bad and your laptop/PC cannot power the R3 mini properly. Did you changed power source when you tried the ch340?

Yes, I changed the power. First with the shipped power adapter + ch341, later I used power from USB-Port from PC/ Laptop. Right now the ch341 won’t give me the serial output. But the r3 mini is connected with usb-c and there’s also the serial output. Maybe the ch341 has some problem or the driver. I ordered another pl2303 for checking.

Do you have fan and case for the R3 Mini or just the PCB? Because this still the expected behavior with bad quality cable/power source. At the beginning, I used my USB-C cable from my phone and tablet, it didnt worked. Then I got a more expensive, quality cable and with that I can power the R3 mini from my notebook for hours without issues with fully spinnig fan.

Yes I have the complete set with case and fan.

I have the following theory:

Power supply + ch340: works as expected, the power adapter does not recognized as a serial device, therefore the serial output of R3 remains the pins
Laptop power + ch340: no output on ch340, probably if USB-C recognized as a serial, the output defaults to that one
Laptop power + USB-C + ch340: the output should be the USB-C serial, but maybe the cable quality is bad and sometimes only recognized as power, and the output switch to the ch340 then back.

I also think there’s some problem with the power. I put a quectel rm520n card in m.2 slot, but it’s not recognised - but maybe also possible that some drivers are missing.

What image do you use?