title: How to program an SPI flash chip with the BeagleBone Black or Teensy 3.1 ...

This document exists as a guide for reading from or writing to an SPI flash chip with the BeagleBone Black, using the flashrom software. A BeagleBone Black, rev. C was used when creating this guide, but earlier revisions may also work.

NOTE: Use of BeagleBone black is for example purposes only, don't buy it unless you want it specifically. There are many ARM Single Board Computers (SBC) that are capable of in system programming (external flashing) and they perform similarly terrible at that task. Common use of devicetrees on those devices allows for configuring them in similar way, but not identical, so a bit of own research is required. Lastly SBC is an example of self-contained device that is capable of flashing, but it's possible to use smaller device like stm32 bluepill with another computer to achieve similar result.

Note: This guide was written for Debian Stretch 9.5, which is the latest operating system for the BeagleBone Black as of June 2019. It is possible that these instructions may be outdated if newer operating systems versions have been released since then.

There was no justification for a further section for the Teensy. Simply refer to this page on flashrom.org for information about how to set it up, and correlate that with the pins on the SPI flash chip as per other guides in the libreboot documentation for each board. At the time of writing, the teensy is tested for flashing on the ThinkPad X200, but it should work for other targets. here is a photo of the setup for the teensy: http://h5ai.swiftgeek.net/IMG_20160601_120855.jpg

Onto the Beaglebone black...

Hardware requirements

Shopping list (pictures of this hardware is shown later):

A Flashrom-compatible external SPI programmer: BeagleBone Black, sometimes referred to as 'BBB', (rev. C) is highly recommended. You can buy one from Adafruit (USA), ElectroKit (Sweden) or any of the distributors listed on BeagleBoard's website (look below 'Purchase'). We recommend this product because we know that it works well for our purposes and doesn't require any non-free software.
Electrical/insulative tape: cover the entire bottom surface of the BBB (the part that rests on a surface). This is important, when placing the BBB on top of a board so that nothing shorts. Most hardware/electronics stores have this. Optionally, you can use the bottom half of a hammond plastic enclosure.
Clip for connecting to the flash chip: if you have a SOIC-16 flash chip (16 pins), you will need the Pomona 5252 or equivalent. For SOIC-8 flash chips (8 pins), you will need the Pomona 5250 or equivalent. Do check which chip you have, before ordering a clip. Also, you might as well buy two clips or more since they break easily. Farnell element 14 sells these and ships to many countries. Some people find these clips difficult to get hold of, especially in South America. If you know of any good suppliers, please contact the libreboot project with the relevant information. If you can't get hold of a pomona clip, some other clips might work, e.g. 3M, but they are not always reliable. You can also directly solder the wires to the chip, if that suits you; the clip is just for convenience, really.
External 3.3V DC power supply, for powering the flash chip: an ATX power supply / PSU (common on Intel/AMD desktop computers) will work for this. A lab PSU (DC) will also work (adjusted to 3.3V).
- Getting a multimeter might be worthwhile, to verify that it's supplying 3.3V.
External 5V DC power supply (barrel connector), for powering the BBB: the latter can have power supplied via USB, but a dedicated power supply is recommended. These should be easy to find in most places that sell electronics. OPTIONAL. Only needed if not powering with the USB cable, or if you want to use EHCI debug.
Pin header / jumper cables (2.54mm / 0.1" headers): you should get male--male, male--female and female--female cables in 10cm size. Just get a load of them. Other possible names for these cables/wires/leads are as follows:
- flying leads
- breadboard cables (since they are often used on breadboards).
- You might also be able to make these cables yourself.
Adafruit sell them, as do many others. Some people find them difficult to buy. Please contact the libreboot project if you know of any good sellers. You might also be able to make these cables yourself. For PSU connections, using long cables, e.g. 20cm, is fine, and you can extend them longer than that if needed.
Mini USB A-B cable (the BeagleBone probably already comes with one.) - OPTIONAL - only needed for EHCI debug or for serial/ssh access without ethernet cable (g_multi kernel module)
FTDI TTL cable or debug board: used for accessing the serial console on the BBB. This page contains a list. OPTIONAL---only needed for serial console on the BBB, if not using SSH via ethernet cable.

Setting up the 3.3V DC PSU

ATX PSU pinouts can be read on this Wikipedia page.

You can use pin 1 or 2 (orange wire) on a 20-pin or 24-pin ATX PSU for 3.3V, and any of the ground/earth sources (black cables) for ground. Short PS_ON# / Power on (green wire; pin 16 on 24-pin ATX PSU, or pin 14 on a 20-pin ATX PSU) to a ground (black; there is one right next to it) using a wire/paperclip/jumper, then power on the PSU by grounding PS_ON# (this is also how an ATX motherboard turns on a PSU).

DO NOT use pin 4, 6, do NOT use pin 19 or 20 (on a 20-pin ATX PSU), and DO NOT use pin 21, 22 or 23 (on a 24-pin ATX PSU). Those wires (the red ones) are 5V, and they WILL kill your flash chip. NEVER supply more than 3.3V to your flash chip (that is, if it's a 3.3V flash chip; 5V and 1.8V SPI flash chips do exist, but they are rare. Always check what voltage your chip takes. Most of them take 3.3V).

You only need one 3.3V supply and one ground for the flash chip, after grounding PS_ON#.

The male end of a 0.1" or 2.54mm header cable is not thick enough to remain permanently connected to the ATX PSU on its own. When connecting header cables to the connector on the ATX PSU, use a female end attached to a thicker piece of wire (you could use a paper clip), or wedge the male end of the jumper cable into the sides of the hole in the connector, instead of going through the centre.

Here is an example set up:\

Accessing the operating system on the BBB

Follow the Getting Started instructions to install the latest version of Debian onto the BBB. It is recommended to download the eMMC IoT Flasher edition, which will write its image to the on-board eMMC.

The operating system on the BBB can be accessed over SSH, with username 'debian' and password 'temppwd'. Follow the instructions on the Getting Started page for complete details.

You will also be using the OS on your BBB for programming an SPI flash chip.

Alternatives to SSH (in case SSH fails)

You can also use a serial FTDI debug board with GNU Screen, to access the serial console.

# screen /dev/ttyUSB0 115200

Here are some example photos:\

You can also connect the USB cable from the BBB to another computer and a new network interface will appear, with its own IP address. This is directly accessible from SSH, or screen:

# screen /dev/ttyACM0 115200

You can also access the uboot console, using the serial method instead of SSH.

Setting up spidev on the BBB

Note: The following commands are run as root. To run them from a normal user account, add yourself to the gpio group to configure the pins and the spi group to access spidev.

Run the following commands to enable spidev:

# config-pin P9.17 spi_cs
# config-pin P9.18 spi
# config-pin P9.21 spi
# config-pin P9.22 spi_sclk

Verify that the spidev devices now exist:

# ls /dev/spidev*

Output:

/dev/spidev1.0  /dev/spidev1.1  /dev/spidev2.0  /dev/spidev2.1

Now the BBB is ready to be used for flashing. The following systemd service file can optionally be enabled to make this persistent across reboots.

[Unit]
Description=Enable SPI function on pins

[Service]
Type=oneshot
ExecStart=config-pin P9.17 spi_cs
ExecStart=config-pin P9.18 spi
ExecStart=config-pin P9.21 spi
ExecStart=config-pin P9.22 spi_sclk
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target

Get flashrom from the libreboot_util release archive, or build it from libreboot_src/git if you need to. An ARM binary (statically compiled) for flashrom exists in libreboot_util releases. Put the flashrom binary on your BBB.

You may also need ich9gen, if you will be flashing an ICH9-M laptop (such as the X200). Get it from libreboot_util, or build it from libreboot_src, and put the ARM binary for it on your BBB.

Finally, get the ROM image that you would like to flash and put that on your BBB.

Now test flashrom:

# ./flashrom -p linux_spi:dev=/dev/spidev1.0,spispeed=512

Output:

Calibrating delay loop... OK.
No EEPROM/flash device found.
Note: flashrom can never write if the flash chip isn't found automatically.

This means that it's working (the clip isn't connected to any flash chip, so the error is fine).

Connecting the Pomona 5250/5252

Use this image for reference when connecting the pomona to the BBB: http://beagleboard.org/Support/bone101#headers (D0 = MISO or connects to MISO).

The following shows how to connect clip to the BBB (on the P9 header), for SOIC-16 (clip: Pomona 5252):

 NC              -       - 21
 1               -       - 17
 NC              -       - NC
 NC              -       - NC
 NC              -       - NC
 NC              -       - NC
 18              -       - 3.3V (PSU)
 22              -       - NC - this is pin 1 on the flash chip
This is how you will connect. Numbers refer to pin numbers on the BBB, on the plugs near the DC jack.

You may also need to connect pins 1 and 9 (tie to 3.3V supply). These are HOLD# and WP#.
On some systems they are held high, if the flash chip is attached to the board.
If you're flashing a chip that isn't connected to a board, you'll almost certainly
have to connect them.

SOIC16 pinout (more info available online, or in the datasheet for your flash chip):
HOLD    1-16    SCK
VDD 2-15    MOSI
N/C 3-14    N/C
N/C 4-13    N/C
N/C 5-12    N/C
N/C 6-11    N/C
SS  7-10    GND
MISO    8-9 WP

The following shows how to connect clip to the BBB (on the P9 header), for SOIC-8 (clip: Pomona 5250):

 18              -       - 1
 22              -       - NC
 NC              -       - 21
 3.3V (PSU)      -       - 17 - this is pin 1 on the flash chip
This is how you will connect. Numbers refer to pin numbers on the BBB, on the plugs near the DC jack.

You may also need to connect pins 3 and 7 (tie to 3.3V supply). These are HOLD# and WP#.
On some systems they are held high, if the flash chip is attached to the board.
If you're flashing a chip that isn't connected to a board, you'll almost certainly
have to connect them.

SOIC8 pinout (more info available online, or in the datasheet for your flash chip):
SS  1-8 VDD
MISO    2-7 HOLD
WP  3-6 SCK
GND 4-5 MOSI

NC = no connection

DO NOT connect 3.3V (PSU) yet. ONLY connect this once the pomona is connected to the flash chip.

You also need to connect the BLACK wire (ground/earth) from the 3.3V PSU to pin 2 on the BBB (P9 header). It is safe to install this now (that is, before you connect the pomona to the flash chip); in fact, you should.

if you need to extend the 3.3v psu leads, just use the same colour M-F leads, but keep all other leads short and equal length (30cm or less). Keep in mind that length isn't inversely proportional to signal quality, so trying out different lengths will yield different results. Same goes for spispeed.

You should now have something that looks like this:\

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License Version 1.3 or any later version published by the Free Software Foundation with no Invariant Sections, no Front Cover Texts, and no Back Cover Texts. A copy of this license is found in ../fdl-1.3.md

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