Introduction:
I recently acquired a BIGTREETECH Pad 7, though my use case for it is not for 3D printing but for another project I plan to document here. Intrigued by its form factor, price and the ability to swap the stock CB1 for a Raspberry Pi CM4, I purchased the Pad 7 alongside a CM4 featuring 8GB of RAM and 32GB of eMMC storage.
Unbeknownst to me at the time, installing a standard Raspbian OS on the CM4 wouldn’t be as straightforward as I had anticipated. Despite my extensive experience with Raspberry Pis, this was my first encounter with a Compute Module. I discovered that installing an OS on the onboard eMMC storage is not as straight forward as I had thought. However, Jeff Geerling provides a detailed guide on how to accomplish this. The problem I ran into was adapting his method for the Pad 7.
Unfortunately, in my search for tutorials on how to accomplish this, I found that most people using the CM4 were opting for the lite version without onboard storage. Here’s how I managed it.
The Problem:
I started with installing the Raspberry Pi USB Boot code. Which can be found in the GitHub repository. I’m working off Windows for this so I was able to get the .exe file from the Win32 directory. This basically allows you to connect to the CM4 and view the eMMC storage as any other USB drive.
This is where I ran into the problem. After installing and connecting the Pad 7 via the USB C port, the device was not being recognized. I double checked the two switches as described in the instructions both were to the right as described for a CM4.
The Discovery:
Looking at Jeff’s tutorial, and others, It was obvious that in order to flash the CM4 it was required to move a jumper. Unfortunately I didn’t see any and before taking the whole Pad 7 apart, I found this video on YouTube.
It was another BTT device, the Manta M4P also CM4 compatible and it was discussing how to install the OS on eMMC storage. On this device it was required to flip a couple DIP switches.
Having noticed the DIP switch block between the USB and CS switches it occurred to me this might be the part of the puzzle I was missing. I also noticed the “Mode” text between the two switch diagrams presumably identifying the DIP switch functions. But I wanted to know what the switches were called on the Manta M4P. This is what I found in the Manta M4P manual on page 21:
The Solution:
So, USB “OTG” and “BOOT”. Looking at the Pad 7 Mode diagram, 3 and 4 are labeled “SOC-BOOT” and “USB-OTG.”
So I flipped them both to the right “ON” position.
I connected the USB cable to my computer, the Pad 7 USB C port, Launched the USB Boot app and pushed the power button on the Pad 7 and:
and the CM4 showed up as a storage device in file explorer. We have connection!
Next step was to launch the Raspberry Pi Imager. I selected the Device, and OS:
Then the moment of truth, clicked “Choose Storage” and:
Success! I proceeded to flash the image to the eMMC storage. This took a while.
Once it was done the storage directory was opened and I had access to the Config files that needed to be modified for the Pad 7.
I removed this line from the cmdline.txt file
console=serial0,115200I then added the following to the config.txt file
#Pad 7 mods
dtoverlay=gpio-led
dtparam=gpio=14,label=Pad7-lcd,active_low=1
hdmi_group=2
hdmi_mode=87
hdmi_cvt 1024 600 60 6 0 0 0
hdmi_drive=1
dtoverlay=dwc2,dr_mode=hostI then powered off the Pad 7, switched the DIP switches back to “OFF”
and booted up.
The Outcome:
SSH in to check the directory and:
That is it, I am up and running. Hope this can help some others running into the same issue.
I will most likely be removing the full version of Raspbian and installing the lite version as I’ll be building a custom interface for my project, more to come on that in a future article. Stay tuned.
Side Notes:
Note 1: as mentioned I am not using the Pad 7 for 3D printing so I skipped the other suggested changes. If you are then follow the manual.
Note 2: I had a typo in my config file settings apparently I had clipped the end of one of them when copying and pasting. So when booting the Pad 7 the screen would flash, I’d see the rainbow square and then it would go black. I did have SSH access, so I was able to SSH into the Pad 7 and edit the config.txt file. It was located in /boot/firmware/config.txt, I edited it using:
sudo nano /boot/firmware/config.txt