P5B Archieven - #Tom's Weblog

In this post I will explain how to flash bios chips with an Arduino. We will be using a Arduino Duemilnove (uno, mega or clones do also work) and a ASUS P5B motherboard that no longer boots after a failed bios update.

Here is an outline of the steps (some of these steps are not strictly necessary but I figured they might help the uninitiated):

Identify board
Find documentation for the board
Locate and identify bios chip
Find documentation for the chip
Find pinout and operating voltages (important)
Prepare the Arduino and installing flashrom
Connecting the Arduino to the chip
Testing
Flashing and verify
Troubleshooting

Identify board and finding documentation

As mentioned in the introduction we are using an ASUS P5B motherboard. The manual of this board can be found on the ASUS website (a direct link can be found in the list of references).

Locate and identifying the bios chip

In the manual we find a board layout that shows the location of the chip, to the right of pci slot 3.

In case the location is not documented we have to find it ourselves. The following page provides instructions on how to locate the bios chip: http://www.bios-chip24.com/Information/Bios-Chip-localization

The next step is to identify what brand and type of chip we are dealing with in order to find the datasheet. Usually the writing on the chip is everything we need as it states the manufacturer and model number. The motherboard manual mentions a “MXIC 25L8005” and if we look at the board we see that the model is indeed a 25L8005 made by Macronix.

Typing the model number into google returns the datasheet as one of the first results. The information we are looking for is the pinout and operating voltage. The following image shows the pinout of the 25L8005:

The pin names do not make much sense if you are seeing them for the first time so the datasheet also include a description of the pin names:

For more information on what exactly the pins do please refer to the datasheet.

Preparing the Arduino

For the Arduino to be able to act as a serial programmer we need to first prepare it using frser-duino. The following command(s) will download and install the required packages, install flashrom, clone frser-duino and flash the Arduino.

sudo apt install git flashrom gcc-avr binutils-avr avr-libc avrdude && git clone --recursive https://github.com/tomvanveen/frser-duino.git && cd frser-duino && make ftdi && sudo make flash-ftdi

Connecting the Arduino to the SPI chip

The following image is an example schematic taken from the flashrom GitHub and shows the pins on the Arduino and the pins on the chip they should connect to (please note that PB0 does not have to be connected):

Emergency edit here: I know understand why people use resistors between the Arduino pins and the chip. The Arduino operates on 5V meaning its logic levels are also at 5V. This need to be brought down to 3.3v using a level shifter.

Flashing the SPI chip

To verify that everything is working correctly we first run flashrom without any operations:

sudo flashrom -p serprog:dev=/dev/ttyUSB0:2000000

The output should look like this:

flashrom v0.9.9-91-g0bfa819 on Linux 4.10.0-28-generic (x86_64)
flashrom is free software, get the source code at https://flashrom.org

Using clock_gettime for delay loops (clk_id: 1, resolution: 1ns).
serprog: Programmer name is "frser-duino"
Found Macronix flash chip "MX25L8005" (1024 kB, SPI) on serprog.
No operations were specified.

If the previous command worked as expected we are now ready for our final step. To write the new BIOS to the chip we use the following command:

sudo flashrom -p serprog:dev=/dev/ttyUSB0:2000000 -w [NEWBIOS]

The output should look like this:

flashrom v0.9.9-91-g0bfa819 on Linux 4.10.0-28-generic (x86_64) flashrom is free software, get the source code at https://flashrom.org Using clock_gettime for delay loops (clk_id: 1, resolution: 1ns). serprog: Programmer name is "frser-duino" Found Macronix flash chip "MX25L8005" (1024 kB, SPI) on serprog. Reading old flash chip contents... done. Erasing and writing flash chip... Erase/write done. Verifying flash... VERIFIED.

And that is it. We have successfully flashed a chip using the SPI interface. If you have any questions or feedback about this post please leave a comment below!