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| == Introduction ==
| | {{#externalredirect: https://www.flashrom.org/supported_hw/supported_prog/serprog/arduino_flasher_3.3v.html }} |
| This explains how to:
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| * Easily lower the voltage of an arduino
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| * Use that arduino to flash a coreboot image on a GM45 Thinkpad with a SOIC16 chip
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| It requires:
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| * An AVR Arduino at 5v
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| * An USB<->Serial adapter capable of providing enough current to power up:
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| ** The arduino
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| ** The flash chip
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| ** The circuits around the flash chip
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| It was tested with:
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| * An Arduino.org "nano version 3.3"
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| * A Sparkfun "FTDI Basic 3v3" (Uses an FTDI FT232R)
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| Caveats:
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| * It requires not to ever connect an USB cable between the Arduino USB port and the computer while the flasher is connected to a flash chip. This would result in the I/O voltage being 5V instead of 3.3V. If you think you may accidentally connect it this way, this flasher isn't the right solution for you.
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| * For now it requires to patch frser-duino
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| == Theory ==
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| In the [http://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-42735-8-bit-AVR-Microcontroller-ATmega328-328P_Datasheet.pdf Atmega328/P datasheet], the "32.3. Speed Grades" chapter describes (pages 368 and 369) the link between maximum frequency of the microcontroller and the voltage. At 3.3v, the maximum frequency is 12Mhz.
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| == HOWTO ==
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| === Build the code and flash it ===
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| ==== Building frser-duino ====
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| First download frser-duino:
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| $ git clone --recursive https://github.com/urjaman/frser-duino.git
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| $ cd frser-duino
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| Then modify the F_CPU value in main.h to be 12Mhz instead of 16Mhz:
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| F_CPU will look like that:
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| #define F_CPU 16000000UL
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| Change it to:
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| #define F_CPU 12000000UL
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| * Flash the Arduino with frser-duino
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| $ make ftdi
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| ==== Flashing the arduino ====
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| Before flashing the arduino we want to make sure that we are talking to the right device.
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| To do that make sure that the arduino is not connected to your computer and run:
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| $ ls -l /dev/ttyUSB0
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| If everything went fine it will output something like that:
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| ls: cannot access '/dev/ttyUSB0': No such file or directory
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| If instead it looks like that:
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| crw-rw---- 1 root uucp 188, 0 27 févr. 14:30 /dev/ttyUSB0
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| then something else is connected to your computer at /dev/ttyUSB0.
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| If you can't figure what's going on by yourself, it's better to get help
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| on the flashrom IRC channel to fix the issue.
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| Then connect your arduino to the computer and run the same command:
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| $ ls -l /dev/ttyUSB0
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| This time it's supposed to output a line that looks more or less like that
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| crw-rw---- 1 root uucp 188, 0 27 févr. 14:30 /dev/ttyUSB0
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| At this point we're pretty confident that /dev/ttyUSB0 corresponds to the arduino, so we can flash it with:
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| $ make flash-ftdi
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| Once it is flashed we can now test that everything went fine with:
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| $ flashrom -p serprog:dev=/dev/ttyUSB0:2000000
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| This will make flashrom talk to the arduino to verify if everything is fine up to this point.
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| If everything went fine it will look more or less like that:
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| $ flashrom -p serprog:dev=/dev/ttyUSB0:2000000
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| /sys/firmware/dmi/tables/smbios_entry_point: Permission denied
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| /dev/mem: Permission denied
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| /sys/firmware/dmi/tables/smbios_entry_point: Permission denied
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| /dev/mem: Permission denied
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| flashrom v1.0 on Linux 4.15.2-gnu-1 (i686)
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| flashrom is free software, get the source code at https://flashrom.org
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|
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| Using clock_gettime for delay loops (clk_id: 1, resolution: 1ns).
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| serprog: Programmer name is "frser-duino"
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| serprog: requested mapping AT45CS1282 is incompatible: 0x1080000 bytes at 0xfef80000.
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| No EEPROM/flash device found.
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| Note: flashrom can never write if the flash chip isn't found automatically.
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| This is the important line:
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| serprog: Programmer name is "frser-duino"
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| It means that flashrom is able to talk to the flasher, which reports itself as "frser-duino"
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| We also have the following line:
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| No EEPROM/flash device found.
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| which tells that it didn't find any flash. This is what's supposed to happen since we didn't connect any yet.
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| === Build the programmer ===
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| ==== Connect the programmer to the USB<->Serial adapter ====
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| To do that:
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| * Connect the FTDI adapter RX to the TX of the arduino
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| * Connect the FTDI adapter TX to the RX of the arduino
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| * Connect the 3V3 of the FTDI adapter to the 5V pin of the Arduino
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| * Connect the GND of the FTDI adapter to the GDN of the arduino.
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| Here's a sumarry of the above:
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| {| class="wikitable" border="1"
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| ! Arduino
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| ! USB<->Serial port adapter
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| |-
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| | RX
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| | TX
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| |-
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| | TX
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| | RX
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| |-
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| | 5v
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| | 3.3v
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| |-
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| | GND
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| | GND
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| |-
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| |}
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| * You can now check that the programmer is responding with:
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| flashrom -p serprog:dev=/dev/ttyUSB0:2000000
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| Since you didn't connect yet a flash chip, it will says it found no flash chips:
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| [TODO]
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| * If you use a clip (Like a SOIC-8 or SOIC16 Pomona clip), connect it to the arduino
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| * Connect the chip to the clip, or if you don't use a clip, the chip to the arduino
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| {| class="wikitable" border="1"
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| ! Arduino pin number
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| ! Function
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| ! Flash chip function
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| ! SOIC8 Flash chip pin
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| ! SOIC16 Flash chip pin
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| |-
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| | D13
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| | CLK
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| !
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| | CLK
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| |-
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| |}
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| * Connect an USB cable between the USB<->Serial adapter and the computer. Never connect the cable between the Arduino USB port and the computer while the flasher is connected to a flash chip. That would result in the I/O voltage being 5V instead of 3.3V.
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| == Flashing ==
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| Run flashrom like that:
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| flashrom -p serprog:dev=/dev/ttyUSB0:2000000
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| With some strange macronix flash chip (that are present in the Thinkpad X200) you might need to add spispeed=100k like that:
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| flashrom -p serprog:dev=/dev/ttyUSB0:2000000,spispeed=100k
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| == Thanks ==
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| Thanks a lot to SwiftGeek on IRC (#libreboot on Freenode) for finding the first workaround to make it detect flash chips at lower voltage. This project would not have been possible without that.
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| == Page license ==
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| This page is available under the following licenses:
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| * [https://creativecommons.org/licenses/by-sa/3.0/legalcode CC-BY-SA 3.0]
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| * [https://creativecommons.org/licenses/by-sa/4.0/legalcode CC-BY-SA 4.0] or later
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| * [https://www.gnu.org/licenses/fdl.txt GFDL 1.3] or later
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