I got my hands on a Wishmesh Repeater that got bricked during an update. But after opening it I saw that there actually was an SWD header and after some googling around I found out that I could use a BMP to reflash the bootloader to unbrick the Repeater.

So I got myself a BlackPill F411CE.

So I opened up the Repeater to solder on a pin header, but had to lift the supercap shown in the picture below. It was glued to the board so I had to carefully cut it free to I could tilt it up and solder on the header.

And now the header is soldered on

Now I need to make my own Black Magic Probe. I downloaded the repo: git clone https://codeberg.org/blackmagic-debug/blackmagic.git

there are some submodule issues since it was recently moved to codeberg so I manually cloned it:

cd blackmagic/deps rm -rf libopencm3 git clone https://codeberg.org/blackmagic-debug/libopencm3.git

Now lets build the code: meson setup build —cross-file=cross-file/blackpill-f411ce.ini -Dbmd_bootloader=true meson compile -C build`

Now we've built the bootloader and the BMP firmware, time to flash my BlackPill F411CE.

Connect a usb cable to the PC to power it.

I actually used an ST-link and STM32CubeProgrammer and flashed the bootloader to 0x08000000 and the BMP firmware to 0x08004000 after a full chip erase.

Confirm that the BMP is now working, on linux run: lsusb And look for something like this: Bus 001 Device 034: ID 1d50:6018 OpenMoko, Inc. Black Magic Debug Probe (Application)

Now connect your new BMP to the repeater SWD port:

And now it's time to flash the bootloader. Download the Wismesh bootloader .hex file from https://github.com/oltaco/WisCore_RAK4631_Bootloader/releases

Now it's time to load up gdb: arm-none-eabi-gdb target extended-remote /dev/ttyACM0 monitor swd_scan

You should get something like: nrf52840 M4 and mrf52840 Access Port You would go for the first.

attach 1 monitor erase_mass load /path/to/WisCore_bootloader.hex monitor reset detach quit

Now unplug the power to the repeater by pulling out the 3v3 and wait ~10 seconds. Connect a usb cable and double press the button and it should now enter DFU mode. Now you can flash the meshtastic firmware.

Congrats! You've unbricked your repeater with a cheap diy debug probe!

Follow the guide on: https://docs.otland.net/ots-guide/running-your-first-linux-web-and-otserver

But install these additional packages

liblua5.4-dev libboost-locale-dev libboost-json-dev

remove “system” from line 103 in CMakeLists.txt in project root remove “Boost::system” from line 168 in src/CMakeLists.txt

Now you can proceed with the rest of the setup

About ten years back I bought a Velleman K7203 as a fun soldering project, and to use as a power supply for a future project.

This will provide a very stable output voltage with <0.5 mV ripple which is pretty nice.

And now, 10 years later, it's time for that future project.

Assembly

The most important thing that was required for PSU after the module itself was a transformer, and preferably toroidal transformer. And those things are not cheap, unless you're lucky and find one second hand.

I got a 230VAC/25VAC 2A transformer that I'm gonna use. And together with that I got a metal enclosure from AliExpress.

I began with drilling holes in the front for the banana plug connectors, and followed the standard pitch of 0.75” between the connectors.

And from the front it will look like this:

After drilling some holes and mounting the power supply and the transformer with some spacers and mounting hardware it looks like this:

I made sure to use a ground cable since I use a metal enclosure, and I also use a C14 connector with a power switch and a fuse as recommended by the PSU manufacturer.

Testing

The PSU in an assembled state is very plain, and it gives a voltage range between 2 to 17.9 V.

Next steps

For now the voltage adjustment is located on the PSU, so one would need to open the case to adjust it. In the future I'd like to have a potentiometer mounted on the front together with a VA meter. And that will be for a future blog post.

What's I2P? Well, it's an alternative to Tor. You can check out at: https://geti2p.net/en/

Or why not get I2P+? https://i2pplus.github.io/

We recently managed to get it working again, and came to the conclusion that it would be a good idea to make a backup of the BIOS on the motherboard, since there may not exist too many backups out there.

I ordered a XGecu T48 Universal Programmer with the appropriate adapters for the flash chip for 59$ If you want to check it out you can find it here: https://xgecu.myshopify.com/products/xgecu-new-t48-tl866-3g-programmer-support-28000-ics-for-spi-nor-nand-flash-emmc-bga-tsop-sop-plcc-9-parts

The T48 is also called TL866-3G and is of course the successor to the popular TL866 universal programmer.

Removing the chip and identifying the model number

Taking a look in the computer, the BIOS flash is located in the PLCC44 socket, but it's a bit hard to reach so the ISA riser card needs to be removed.

A closer look at the chip shows a sticker and a serial number that points back to 94.

Removing the chip was easy because of the included chip removal tool. Just place the hooks in the slots in the corners and press until it pops out.

Now I needed to find out what type of flash chip it really was. But I'd rather not ruin the sticker. So I used a scalpel blade to carefully remove the sticker so I could read the model number. (Pardon for the out of focus photo)

A quick google search told me that it was an Intel N28F001BX-T150 1Mbit (128KB) Boot block flash memory.

Reading the flash using Xgpro

(Sadly during the migration to another server, the pictures where lost in this part)

The program used for the T48 is the Xgpro. The first thing I did was to make sure the right IC was selected by clicking “Select IC” in the upper left corner.

After marking the correct IC and clicking “Select” I clicked on “READ” in the upper toolbar. Now a new window appeared with a picture on how to seat the chip in the adapter and the ZIF socket. After connecting it according to the picture I clicked “Read” and the “BACK”

Now I could see the data from the chip. Scrolling down a bit, I could find some readable text like a Copyright from 1984 and an AST Research Copyright from 1995. Cool!

After confirming that I got some data from the chip I saved it to a .bin file using the “SAVE” button on the top left.

My plan is to upload the bin file to a site like The Retro Web, this page in particular: https://theretroweb.com/motherboards/s/ast-advantage!-610-611-486-202728-101 So people can find a copy of the BIOS and easily flash a new one if they ever need to do that.