I have a BananaPi R4 that I bought from Amazon late October 2025 as a router kit with WiFi7 card and case. I run OpenWrt that is locally built from source flashed onto an SD card. I also have the UART cable setup to see serial logs for debugging. I recently rebuilt OpenWrt image, flashed it on an SD card, and it worked fine. I was able to setup WiFi interfaces using LuCI. Then I flashed another SD card using the same image as backup, turned it on, then everything stopped working. I no longer see serial logs, and the WiFi interface doesn’t seem to work and I cannot access LuCI anymore. I took all basic precautions while swapping out the SD card. The green “G” LED next to the PWR red LED turns on after boot. I ruled out UART issue by swapping out the UART cable from the faulty R4 with another R4 that still works, and I see serial logs just fine. Based on my research, it looks like some sort of u-boot issue, and I may need to do an SPI reflash. Unfortunately, I don’t have serial logs because I don’t see them on the serial console. Does anyone know how to fix this? Thank you! CC: @frank-w
You need to check if your new SD card is working correctly. I had a similar experience where a working OS image that ran on one card stopped working after being written to another. The reason was a defect in the card.
I tried a working SD card from a slightly older R4, but it did not make any difference. Even if I don’t put an SD card, there should be serial logs, which I don’t see either. So I don’t think SD cards is the issue.
You need to make sure that you are writing a working image and that no errors occur during the writing process to the memory card.
I tried two SD cards with an image build several months ago, and another one build this week. They both work just fine on my slightly older R4, and shows serial logs. Neither card works on my new R4, and I don’t see any serial logs.
Excuse me, I didn’t quite understand you correctly. So you have two R4s, an old one and a newer one. Everything works on the old one, but the new one refuses to start with any of the cards that worked on the old R4. Is that right?
Correct. But the new one used to work until 2 days ago – I used to see serial logs, and I was able to setup WiFi radios using LuCI. Then I flashed SD1 using a new image, it worked fine. Then I flashed SD2 with the same new image, tried it on the new R4, and everything stopped working. Now I don’t see serial logs, and I am unable to connect to LuCI. The older R4 works fine.
There’s clearly some kind of problem here, either the kernel isn’t loading, or there’s a malfunction in the card reader.
To begin with, I would check the card reader. Can it read cards with other images?
Have you tried changing power supply?
You should see bootrom at serial even when sdcard is not detected.
To begin with, I would check the card reader. Can it read cards with other images?
Card reader on the BPI-R4 board?
Yes, I have tried changing the power supply from the older (working) BPI-R4, but still no serial logs.
Where are you inserting the card?
Unfortunately, I don’t have an R4, but I do have a BPI-F3 and a Milk-V Jupiter. The Jupiter is connected to the BPI-F3 via a terminal. Minicom is running on the latter. With the Jupiter powered off, I remove the memory card and then power it on. The following information appears in the Minicom terminal:
Спойлер
minicom.txt (14,7 КБ)
If you remove the memory card, will something like this appear on the terminal screen?
Where are you inserting the card?
In the BPI-R4’s SD card slot. This is not the first time I am trying it. It worked well for 2+ months. The same card works well on my older BPI-R4.
I meant, doesn’t the “SD card slot” read microSD cards for booting?
Yes. SD = microSD. You can’t insert a regular SD card on the BPI-R4.
Overall, this doesn’t really matter. The most important thing is that the “SD card slot” is indeed a data reading device, but not in the classic sense of a “card reader”. This is a pointless argument, let’s stop. So, what kind of errors are you getting in the terminal? I would like to see more details.
Also, make sure BootStrap Switch that all Jumper is “1”, BPI-R4 will boot from SD card.
Yes, they are. I set it to 1 1 as mentioned in the documentation a couple of months ago, and I never changed it.
how about switching to nand or emmc ? anything showing ?
also, are you able to ssh ? (noting you see the green light)
Have you checked serial pins that there is no broken soldering point or similar?