mirror of https://github.com/OpenIPC/wiki.git
Add initial draft of flash chip interfacing guide.
Matt Davis
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# OpenIPC Wiki
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[Table of Content](../README.md)
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Flash Chip Interfacing
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--------------------
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This is an advanced topic regarding identifying, reading, writing, verifying and
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erasing flash chips by interfacing directly with the flash chip using a programmer.
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This is not the preferred method of flashing the firmware, but it certainly can be useful
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when other methods fail.
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If you are just getting started, you are probably in the wrong place: check out
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[Installation](installation.md) and [Burn Example](burn-example.md) for better starting points.
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SOIC8 Chips
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--------------------
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SOIC8 is a common package for flash chips. It is a small package with 8 pins, and
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the pins are spaced 1.27mm apart. The pins are numbered counter-clockwise starting
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from the top left corner with the dot marking. The top left pin is pin 1, the top right pin is pin 2,
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As mentioned in [Help: U-Boot](help-uboot.md) the SOIC8 flash chip can sometimes be tricked
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into going straight to u-boot mode, and the following diagram is shown:
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SOIC8 Clips
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--------------------
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SOIC8 clips are a convenient way to interface with SOIC8 chips. They are cheap and somewhat easy to use.
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Remember though, that the clip requires a programmer to act as interface between the clip and your computer.
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Here is an example of a SOIC8 clip wired to a Raspberry Pi Pico:
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Picking a Programmer
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--------------------
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### CH341A
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There are many programmers available, and they all have their pros and cons. The most popular
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programmers are boards leveraging the CH341A, which is a cheap and easy to use chipset. For more details about the CH341A,
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see [CH341A Hardware Programmer](hardware-programmer.md).
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### Raspberry Pi Pico
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The Raspberry Pi Pico is a microcontroller board with a USB port and a several GPIO pins. It is also cheap and easy to use,
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and maybe you already have one lying around. Doesn't matter if it is a wireless version or not, they both work the same.
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In order to use the Pico as a programmer, you will need to put the pico into bootloader mode by holding down the BOOTSEL button
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while plugging it into your computer. The Pico will show up as a USB drive, and you can drag and drop the uf2 file onto the drive.
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Currently, the best pico-serprog library to use is a fork of [pico-serprog](https://github.com/opensensor/pico-serprog)
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which fixed a number of issues encountered with the original.
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There are more instructions the pico-serprog Github, however pico-serprog firmware will grant you
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an extra USB COM port that maps to the following GPIOs.
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| Pin | Function |
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|-----|----------|
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| 7 | CS |
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| 6 | MISO |
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| 5 | MOSI |
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| 4 | SCK |
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Since most SOIC8 flash chips are 3.3v, you will need to connect to the 3.3 V rail of the PICO which is pin 36,
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and remember to connect the GND pin as well, there are many GND pins on the pico, such as pin 38.
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* Note: if for some reason your chip needs 5V, you can use VSYS which is pin 40 instead of 3.3V, but make sure you read the specification of your specific flash chip.
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Flashrom program
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--------------------
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Flashrom is a program that can be used to read, write, erase, and verify flash chips. It is available for Linux, Windows, and Mac.
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Generally these days, you need to compile it for the platform that you intend to use it on. It is a command line program, and
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there are many options available. The following are some examples of how to use flashrom.
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This guide focusing on using flashrom and does not currently explain building flashrom, but you can find instructions on the [flashrom website](https://flashrom.org/).
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### Determine your COM port
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For windows, you can use the device manager to determine the COM port that your programmer is connected to.
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For Linux, you can use the `dmesg` command to determine the COM port that your programmer is connected to.
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### Reading a flash chip
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To read a flash chip, you sometimes need to know the type of flash chip that you are reading.
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Try running simple probe to verify you get connectivity with the programmer. pico-serprog is a serprog (or serial programmer) and that needs to be specified to flashrom.
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In this example, the programmer is connected to COM23, and the baud rate is 2000000 which is known to work well and can read a 16MB flash chip in 2-3 minutes.
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```bash
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./flashrom.exe -p serprog:dev=COM23:2000000 -V
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```
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Here is an example of reading a flash chip. In this example, flashrom had told us we had to pick between three different chips, and we picked the "GD25B128B/GD25Q128B".
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```bash
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# ./flashrom.exe -p serprog:dev=COM23:2000000 -c "GD25B128B/GD25Q128B" -r gokev300-camera-12242023.bin -VV --force
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flashrom 1.4.0-devel (git:v1.2-1386-g5106287e) on Windows 10.0 (x86_64)
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flashrom is free software, get the source code at https://flashrom.org
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Using clock_gettime for delay loops (clk_id: 1, resolution: 100ns).
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flashrom was built with GCC 13.2.0, little endian
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Command line (8 args): C:\msys64\home\matte\flashrom\flashrom.exe -p serprog:dev=COM23:2000000 -c GD25B128B/GD25Q128B -r gokev300-camera-12242023.bin -VV --force
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Initializing serprog programmer
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Baud rate is 2000000.
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serprog: connected - attempting to synchronize
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.
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serprog: Synchronized
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serprog: Interface version ok.
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serprog: Bus support: parallel=off, LPC=off, FWH=off, SPI=on
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serprog: Maximum write-n length is 32
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serprog: Maximum read-n length is 32
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serprog: Programmer name is "pico-serprog"
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serprog: Serial buffer size is 64
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Warning: Automatic command availability check failed for cmd 0x07 - won't execute cmd
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Warning: NAK to query operation buffer size
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serprog: operation buffer size is 300
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serprog: Warning: Programmer does not support toggling its output drivers
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The following protocols are supported: SPI.
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Probing for GigaDevice GD25B128B/GD25Q128B, 16384 kB: compare_id: id1 0xc8, id2 0x4018
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Added layout entry 00000000 - 00ffffff named complete flash
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Found GigaDevice flash chip "GD25B128B/GD25Q128B" (16384 kB, SPI) on serprog.
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Chip status register is 0x00.
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Chip status register: Status Register Write Disable (SRWD, SRP, ...) is not set
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Chip status register: Block Protect 4 (BP4) is not set
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Chip status register: Block Protect 3 (BP3) is not set
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Chip status register: Block Protect 2 (BP2) is not set
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Chip status register: Block Protect 1 (BP1) is not set
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Chip status register: Block Protect 0 (BP0) is not set
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Chip status register: Write Enable Latch (WEL) is not set
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Chip status register: Write In Progress (WIP/BUSY) is not set
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This chip may contain one-time programmable memory. flashrom cannot read
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and may never be able to write it, hence it may not be able to completely
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clone the contents of this chip (see man page for details).
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===
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This flash part has status UNTESTED for operations: WP
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The test status of this chip may have been updated in the latest development
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version of flashrom. If you are running the latest development version,
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please email a report to flashrom@flashrom.org if any of the above operations
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work correctly for you with this flash chip. Please include the flashrom log
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file for all operations you tested (see the man page for details), and mention
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which mainboard or programmer you tested in the subject line.
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Thanks for your help!
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serprog_delay used, but programmer doesn't support delays natively - emulating
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Block protection is disabled.
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Reading flash... read_flash: region (00000000..0xffffff) is readable, reading range (00000000..0xffffff).
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done.
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```
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### Writing a flash chip
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Writing a flash chip is quite similar to reading it. You need to specify the COM port, the baud rate, and possibly the chip type.
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Simply change your arguments to flashrom to include the -w option and the file that you want to write to the flash chip.
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```bash
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./flashrom.exe -p serprog:dev=COM23:2000000 -c "GD25B128B/GD25Q128B" -w openipc-hi3516ev300-ultimate-16mb.bin -VV --force
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```
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During a write operation, flashrom will first read the entire chip, then erase and write the chip, and then re-read it to verify.
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Always make sure you successfully back up and complete a read cycle before attempting to write to a chip.
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### Conclusion
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This guide is not meant to be a complete guide to using flashrom, but rather a starting point for those who are interested in using it,
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and also inspiration for those who have raspberry picos lying around and want to use them for something useful.
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If you liked the pico-serprog example, you probably will also really like the [pico-uart-bridge](https://github.com/Noltari/pico-uart-bridge)
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which gives multiple COM ports over a single USB connection, for the purpose of connecting UART terminals.
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