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Revision as of 09:23, 21 February 2013 by GNUtoo (talk | contribs) (Pictures (With the 3.3V SPI levels))
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This page is a first draft only and serves to collect information about the serprog protocol and the programmers implementing it.


See serprog-protocol.txt in the source tree. It is designed to be compact and allow efficient storage in limited memory of programmer devices.


AVR flasher by Urja Rannikko

Prototype RS232 AVR parallel flash programmer

The Prototype RS232 AVR parallel flash programmer Urja Rannikko was the first implementation of the serprog protocol.

FIXME: AVR source code is somewhere in the coreboot mailing list archives...

AVR flasher by eightdot

FIXME: Link?

Arduino Mega flasher by fritz

[1] [2] [3] FIXME: More info?

InSystemFlasher by Juhana Helovuo

This is one talks to SPI devices via serial over USB. Details can be found in the coreboot wiki and in this coreboot mailing list thread.

atmegaXXu2-flasher by Stefan Tauner

Like the InSystemFlasher this one uses LUFA on an AVR microcontroller to tunnel the serial data over USB.

atmegaXXu2-flasher with Pomona SOIC hook attached

Arduino flasher by GNUtoo

WARNING,if you don't add the resistors, the SPI levels are at 5V, while I tried it with 3.3V chip and that it worked(but DIO was at 4.3v which was over the maximum of 4v, during all the time that the chip was connected to the programmer), it may not work for you and break the chip...

This flasher require the following hardware parts:

  • An arduino uno or an arduino Duemilanove(way faster) and its usb cable
  • some wires(optionally some connectors to solder on(for easier plugin and more reliability)
  • a 10k resistor
  • 3 x 10k resistors (for the 3.3v version)
  • 3 x 15k resistors (for the 3.3v version)
  • A flash chip with the following characteristics:
    • supported by flashrom
    • SPI
    • 3.3v or 5v(the arduino has a 3.3v and a 5v output, only 3.3v was tested...)

Pictures (With the 5V SPI levels issue)

Building (With the 5V SPI levels issue)

Left pins of the BIOS chip:
[pin1 of the bios chip] /CS<->10k resistor<->VCC 

[pin1 of the bios chip] /CS<->Arduino pin10(SS, PORTB2)
[pin2 of the bios chip] DO<->Arduino pin12(MISO, PORTB4)
[pin3 of the bios chip] /WP<->VCC
[pin4 of the bios chip] GND<->GND on the power pins

Right pins of the BIOS chip:
[pin8 of the bios chip] VCC<->+3.3V on the power pins of the Arduino
[pin7 of the bios chip] /HOLD<->VCC
[pin6 of the bios chip] CLK<->Arduino pin13(SCK, PORTB5)
[pin5 of the bios chip] DIO<->Arduino pin11(MOSI, PORTB3)

The Bios chip used is a W25X80. 
The Arduino is an arduino uno.

Pictures (With the 3.3V SPI levels)

WARNING, I was told that by Simon Inns by mail: "The 3V3 fritzing example on the Wiki (the diagram of

the breadboard) is quite wrong... The 3V3 output from the Uno is shorted to GND and the CLK and DI pins of the EEPROM are connected together after the 10K resistors. Might be a good idea to fix it before you get "You broke

my Uno" emails ;)"

Improved 3.3v version by Simon Inns (no issue anymore with laptop chips)



git branch Compatible Arduino version flashrom arguments Comments
  • Arduino uno
-p serprog:dev=/dev/ttyACM0:2000000
  • reliability issues (flashrom blocks waiting for data from the arduino indefinitely) with the code that is in the 8u2/16u2 beeing investigated...
  • Arduino Duemilanove
  • Arduino uno with an external FTDI serial<->usb adapter or any other kind of adapter capable of 2000000 bps
-p serprog:dev=/dev/ttyUSB0:2000000
  • Works flawlessly
  • Very fast


# time flashrom -p serprog:dev=/dev/ttyACM0:2000000 -r coreboot.rom
flashrom v0.9.5.2-r1541 on Linux 2.6.38-14-generic (x86_64)
flashrom is free software, get the source code at

Calibrating delay loop... OK.
serprog: Programmer name is "serprog-duino"
Found Winbond flash chip "W25X80" (1024 kB, SPI) on serprog.
Reading flash... done.

real	0m16.602s
user	0m0.930s
sys	0m0.000s
# time flashrom -p serprog:dev=/dev/ttyACM0:2000000 -w build/coreboot.rom
flashrom v0.9.5.2-r1541 on Linux 2.6.38-14-generic (x86_64)
flashrom is free software, get the source code at

Calibrating delay loop... OK.
serprog: Programmer name is "serprog-duino"
Found Winbond flash chip "W25X80" (1024 kB, SPI) on serprog.
Reading old flash chip contents... done.
Erasing and writing flash chip... Erase/write done.
Verifying flash... VERIFIED.          

real	0m39.548s
user	0m2.650s
sys	0m0.000s

Required software

To make it work you need:

Building the software

$ svn co svn:// flashrom
$ cd flashrom && make
$ cd ../
$ git clone git://
$ cd serprog-duino && make && make upload

Running flashrom

./flashrom -p serprog:dev=/dev/ttyACM0:2000000


  • SST25VF016B => huge issues, not recognized by the 3.3v version, had to use the 5v version which is over maximum allowed voltage, also had to lower the serial speed to 115200, ultra slow to write(seem related to the chip itself, since that with the openmoko programmer it's even slower...)...
  • W25X80 works well in 3.3v mode(5v works also but it's highly not advised to use 5v)

Advantages and disadvantages

  • The speed isn't that great(about 3 minutes for reading+writing+verifying a 1M chip)
  • The speed is now much better thanks to a patch by Sebastian Parborg.
  • it is made of very commonly available parts(if you can find an arduino uno, you will be able to build it).
  • Voltage issues( SPI levels are at 5v, it's problematic for flashing 3.3v chips...)


  • Find a way to lower the voltage to 3.3v
  • Fix the arduino UNO speed and reliability issues