Mounting the BB-400 to a PC
The BB-400 has a mini-USB connection port integrated onto the device, which is primarily used for editing the device’s YAML file. This is a key feature as it allows the user to edit the devices configuration settings without turning the device on. It should be noted that the device should never be turned on when performing this process.
The BB-400’s YAML file is stored on the /boot partition of its internal storage, by placing it here we have ensured that the configuration of the devices settings is one of the first tasks performed as the device is turned on. Another nice feature of being able to edit the YAML file without the device being powered is that we can safely assume the device’s setup before it has been turned on.
The process of editing the YAML file through the mini-USB is quite simple, however, your device must be reconfigured before it will be able to perform this process safely.
Some important things to note are:
- Make sure the device is not connected to any power source
- Once the reconfiguration process has been completed, all changes made to the device need to be reverted before reusing the device, and should be done so while the device is unpowered
- The following reconfiguration steps need to be performed precisely otherwise you could cause damage to the device.
Reconfiguring your device
Follow the steps below when your device is fully powered off, to ensure you correctly set your device before editing the YAML file through USB. Editing the BB-400’s YAML file, located on the /boot partition of the devices internal storage begins by adjusting a changeable jumper inside the device. Prior to adjusting the jumper the outer shell of the BB-400 needs to be removed so that the internal PCBs and jumper can be located.
1. Removing the case of the BB-400
To open the case, take a small flat-head screwdriver and locate the 4 self-locking tabs which hold the 2 sections of the BB-400’s case together. Using a flat-head screwdriver, gently push the pins down and inwards so that they unhinge themselves. Once all 4 tabs have been released, the halves of the device will now be free to separate from one another. Take care when removing the head of the device from the body as the PCBs and internal hardware will now be fully exposed.
Please take care not to damage the ribbon cable.
DO NOT touch anywhere near, or around the 2 Large Blue super capacitors if the device has been powered on within the last 24 hours. Accidentally shorting together the pins for both super capacitors with either skin or jewellery can cause a rapid discharge of the super capacitors. While the discharge voltage isn’t large enough to prove fatal, it will cause significant burns to the contact area.
2. Adjusting the Normal jumper to Flash jumper
Having released the internal hardware from the protective case, we now need to locate the Normal/Flash jumper located on the PCB. Inside the BB-400, there are 3 PCBs, the smallest of the three being the Raspberry Pi, and the two larger ones are for the BB-400’s hardware. While holding the device flat, move the PCB with the 2 large super capacitors to face upwards. To find the jumper, look on the reverse PCB and it is placed near one of the edges, labelled as ‘Mode’. The jumper sits over a 3-pin connector, which by default is set in the ‘Normal’ mode. In order to edit the YAML file over USB we need to move this jumper into the ‘Flash’ position. The jumper should be removed and replaced covering the middle and right pin, the different modes have printed names near the port to help you identify which pins are which.
This completes the hardware changes needed for this process, now place the device back into its protective casing, making sure the boards slip into the channel grooves on each edge. This will protect the device from damage and the user from any potential injury.
The next stage involves downloading software from the official Raspberry Pi website to allow the compute module to be turned into a mass storage device.
Raspberry Pi Software Process
Although the Raspberry Pi website outlines the process using Linux and Windows, the Windows process is also detailed below.
- Download and run the RPiBoot.exe Windows installer, this will install the relevant drivers and the boot tool you will need.
- Connect a USB cable from the BB-400 to the PC which you are performing this process on. The jumper on the BB-400 must be in the ‘Flash’ position at this stage.
Note: if you are following the Raspberry Pi guide, they refer to this step as the following: “Ensure J4 is set to the EN position”.
- Apply power to the BB-400. Windows should now automatically find your hardware and install the correct driver.
- Once the driver is installed, run RPiBoot.exe, which you should have installed in step 1.
- After a few seconds, the compute module eMMC will appear as a USB mass storage device (Under Windows).
Edit the YAML file
Having performed the steps above, you should now be able to access your BB-400 as though it were a USB storage device. On Windows, open the file explorer and find the BB-400; the device might be listed as a ‘Mass Storage Device’. Open the device’s storage, and the /boot partition. In this partition you should see a file called ‘bb config.yaml’. This is the configuration YAML file for your device. Ensure you open the file with a text-editor (we recommend WordPad) to see all of your settings and their sub-sections loaded correctly for you to edit.
Once you have edited the YAML file, ensure that you save your changes before performing any of the final steps.
Change Mode jumper back to ‘Normal’
In order to return the device back to an operational state, we need to reverse the internal jumper we changed previously. Completely unplug the device from any source of power and make sure the Stopping LED has switched off, this will take around 5-7 minutes. It is important to make sure the device has fully powered down, so any remaining charge in the super capacitors discharges itself safely. Once the device has switched off, you can safely open the device, again using the screwdriver and self-locking pins. Locate the jumper connector and move the jumper back to the ‘Normal’ position. This step ensures the BB_CLI is able to issue commands and change settings but also to keep the device operational. The PCBs can then be safely placed into the case and the device can now be powered on again. If this process was successful, then the device will start with the new configuration setup specified in the YAML file.