Raspberry Pi 4B POE Touchscreen Case

Case for a Raspberry Pi 4B with Touchscreen, POE and 2x external I2C (electrically isolated long range as well as short range) that can be used at the same time (as shown in the cover photo).

You will need:

• Prusament PETG V0
• Raspberry Pi 4B (I use the 8GB RAM version)
• SoC heatsink (40 x 30 x 5mm, Amazon ASIN B0C7H2DDX5)
• RAM heatsink ( 14 x 7 x 3mm, Amazon ASIN B0BLZ2BHB5)
• 2x heatsink for USB and Ethernet chips (7 x 7 x 3mm, Amazon ASIN B0CSJXPLLR)
• microSD card (32GB or more, I use Kingston Industrial)
• Waveshare 4.3" DSI IPS Touchscreen (Amazon ASIN B083Q8YLVP)
• Waveshare POE hat type C (Amazon ASIN B0928ZD7QQ)
• 4x 10mm spacers (Amazon ASIN B0C1FY87PY)
• KKSB 30mm 5V DC PWM fan (Amazon ASIN B0BJFCBJXX)
• Adafruit 4756 LTC4311 I2C extender
• Adafruit 4903 ISO1540 I2C isolator
• P82B715 I2C bus extender chip (and optional IC socket)
• Capacitor 100nF
• Capacitor 100uF (I use Tantal)
• 2x resistor 330R
• 2x 3.5mm TRRS socket
• Assorted pin headers
• Assorted socket strips
• Some breadboard wires (these are cut to the required length)
• A dot matrix PCB (cut, drill and file to get the required pieces)
• 4x rubber feet

For the remote side of the long range I2C extension you will additionally need:

• P82B715 I2C bus extender chip (and optional IC socket)
• Capacitor 100nF
• 2x resistor 4K7
• Probably a breadboard, a TRRS socket and two TRRS plugs as well as some proper wire to create a cable with plugs and a power supply (either 3.3V or 5V)

Finally you will need patience and you must be willing to work in a tight and cramped space. And you need to have adequate soldering capabilities for regular sized components (the SMD stuff is already assembled on the Adafruit PCBs).

The above Amazon ASINs are for reference only. Some of the Amazon references do contain the required parts as elements of a bundle. If you have problems to find the required electronics search e.g. DigiKey.

Note that the power/HDMI/audio cover as well as the back plate do come with supports when printed. Remove these (outer rim support and screw hole supports)!

The schematics for the DIY components can be found in the attached PDF. Prepare this stuff first. You can have a look at the supplied photos for an idea how this can be done.

Remove the fan from the POE hat and install the KKSB fan instead - but on the other side of the POE hat PCB.

Then assemble the Raspberry Pi including microSD and heatsinks. Make sure that the SoC heatsink doesn't collide with the POE hat components. Mount the Raspberry Pi directly to the display using the POE hat spacers, do not use the short spacers that come with the display (they are used later). Install the DSI cable and test that Pi and display work.

Install the POE hat on top of the Raspberry Pi, use three of the short spacers that did come with the display and one of the screws that did come with the display or the POE hat (see photos).

Install the I2C add on PCB on top of the POE hat using three of the screws that did come with the display or the POE hat. Make sure all connectors for fan and I2C are in place.

Create the display mounting spacers by adding a nut that comes with the display or the POE hat to each of the extra 10mm spacers and the mount each of the extra spacers on top of the long spacers that come with the display.

Install the TRRS sockets into the proper breakouts and install the LTC4311 board with the connector PCB into its holder. Add the power/HDMI/audio cover as well as the ethernet/USB cover to the PCB stack.

Insert the resulting pack into the base case, you will have to bend the side that will receive the LTC4311 breakout slightly outwards with your fingers for the pack to slide in (required for display only). You can temporarily and loosely mount the display spacers for easier insertion.

If you did use the display spacers for insertion, remove them now. The four inserts go between the display socket and the display spacers. There are holes in the case walls that fit the inserts. Insert each insert and then mount the associated extended display spacer. Though this is fiddly it keeps the display in the proper position with respect to the case.

Now do test that everything works as expected. Then insert the remaining I/O cover and install the back part. Use four of the screws that did come with the display or the POE hat to close the case. Finally install four rubber feet, these are needed as there are ventilation holes on the back of the case.