An In-Depth Look at the Raspberry Pi 400

Let's take an in-depth look at the Raspberry Pi 400. What exactly is it, who is it for and, most importantly, what’s inside?  

What is it?

The Raspberry Pi 400 is a Raspberry Pi 4 built into a keyboard. Because it is basically a Raspberry Pi 4, the Raspberry Pi 400 has almost the same specifications as the Raspberry Pi 4 with 4 GB of memory. As such it also has Wi-Fi and Bluetooth. There are some differences, however.

To fit the Raspberry Pi 4 inside a keyboard while keeping its connectors accessible, the board has been redesigned. Most of the Raspberry Pi 4’s connectors, including the 40-pin extension connector, are available at the rear side of the device, but not all. More on that below.

What can you do with it?

The Raspberry Pi 400 is quite a powerful keyboard computer with Wi-Fi and USB. All that is needed to surf the Internet or play games is to connect a monitor and a mouse to it. The Raspberry Pi is, of course, intended to learn programming on, and so you can do that too. The extension connector lets the Raspberry Pi 400 control things by plugging custom-built interfaces on it.

 

No Scratch

The Raspberry Pi 400 is targeted more at programming-minded users than at makers. The Kit comes with the Official Raspberry Pi Beginner’s Guide (download e-book for free), which has many programming examples for both Scratch3 and Python. However, although the book has 40 pages on programming with Scratch3, the tool isn't included on the microSD card. The 40-pin expansion connector at the back can be used to connect home-brew equipment to, so tinkerers are welcome too.

History repeating

Due to its shape and extension connector in the rear, the Raspberry Pi 400 reminds of computers from the eighties like the Commodore 64, the VIC-20 and the ZX Spectrum. Looking up these classics, I came across a citation concerning the BBC Micro Model B which, I feel, fits the RPi 400 perfectly: “a no-compromise computer that has many uses beyond self-instruction in computer technology.”
 

Soft power On/Off button

Compared to the Raspberry Pi 4, the Raspberry Pi 400 is more accessible to newbies, simply because it is nicely packaged. It also has a soft power On/Off button, which is good. I did find its behaviour a bit quirky, though. It powers down when you release the button. Sometimes you have to press it for five seconds or so, sometimes only for one, and sometimes it results in a reboot.

So, what’s inside?

Being familiar with Raspberry Pi boards, the urge to open the Raspberry Pi 400 to see what is inside is strong. Opening it is easy enough as the keyboard is simply clipped to the bottom shell. There are many clips, about every 4 cm all around. Once all the clips are undone, you must carefully rotate the topside towards you because the two parts are held together by the keyboard flexible flat cable (FFC).

Carefully lift the lid on the connector and slide the cable out. You now have two separate parts. Put the keyboard aside, it has nothing removable in it.
 

We continue with the bottom part. Most of what’s inside is hidden by a metal plate, the heat sink, fixed by four tiny screws to the bottom shell. Remove the screws. Now lift the metal plate, but carefully, as it is stuck to the CPU with heat-conducting adhesive tape. With a thin metal tool like a long knife, you can detach it from the processor.

Now the circuit board is visible. Except for its shape, most parts on the board are identical to the ones on a Raspberry Pi 4. It is held in place with two clips and can be removed easily.

Faster CPU?

The CPU on my Raspberry Pi 4 is labelled '2711ZPKFSB06BOT', whereas the CPU on the 400 has '2711ZPKFSB06COT' printed on it. The specifications of the RPi400 mention a clock frequency of 1.8 GHz; this is "only" 1.5 GHz for the RPi4. The RPi 400 is therefore 20% faster than the RPi4 (unless the RPi4 has been updated too).

USB keyboard

The power supply looks a little bit different, and also the Ethernet connector with its external transformer. New is, of course, the keyboard connector and the IC next to it, a Holtek HT45R0072. This is an 8-bit microcontroller with USB interface. Its datasheet shows one typical application: a USB keyboard, exactly what we have here. Following the traces on the bottom of the PCB, we see that it is connected to the VIA VL805 USB 3.0 host controller. As this is a four-port device, we now understand why there are only three USB connectors left on the Raspberry Pi 400.

No boot EEPROM?

Next to the USB controller is an empty footprint. On the Raspberry Pi 4 this part is populated, there are even two of them, and it appears to be the boot EEPROM. One of its tasks is to replace the file bootcode.bin found in the boot partition of the SD card. A reason not to mount the EEPROM is to save some money, another might be to avoid corrupting its contents (by clumsy users), limiting stress on the aftersales department.

 

Missing in action: camera, display & A/V connectors

The Raspberry Pi 400 did not inherit the camera, display, and analogue A/V connectors. Dropping the display and A/V connectors seems logical as sound and video are transported perfectly fine over HDMI (of which there are two); the camera can simply be replaced by a USB webcam.

The microSD card connector finally has become a push-push type, which makes replacing the SD card much easier than on other Raspberry Pis, especially when these were mounted inside a case. For cost, size or other reasons, the Ethernet connector does not have LEDs anymore.

Heat sink

A metal plate almost as large as the keyboard provides cooling for the CPU. I guess it is supposed to be connected to ground as the PCB has a large opening in the solder mask on the ground plane at the position where the heat sink has a tab going down to the PCB. The two should probably touch, but in my sample they don’t.

 

Want more memory?

The Raspberry Pi 400 does not have the possibility to replace the memory by a bigger one or add more. For the moment there is only one model, so unlike the Raspberry Pi 4 or the Compute Module 4 (CM4), you cannot replace the board by one with more options. Maybe some variants will follow soon?

Is the Raspberry Pi 400 for you?

The Raspberry Pi 400 is a well-designed, easy-to-use, and low-cost product for people interested in Python programming on a Linux platform, or just as a cheap computer to surf the Internet with. Its friendly looks will definitely attract users who, up to now, might have been intimidated by the bare Raspberry Pi boards.

The flip side is that the Raspberry Pi 400 with its consumer-product looks will appeal to an audience not necessarily used to paying attention to technical subtleties. Therefore, some sort of protection of the 40-pin expansion header would have been a welcome addition.

Originally, the Raspberry Pi was created with the intention to make computing and programming accessible to people with few resources. However, it quickly found its way into multimedia servers and retro-gaming arcades instead. Maybe the Raspberry Pi 400 is how it should have been done from the start? Maybe this time it will end up in the hands of the original target group?