deltabeard/cmio

Custom Raspberry Pi Compute Module (1/3) IO Board

cmio's Issues

Possibility of moving some components to the bottom side

Add voltage test points

RAM slot has incorrect footprint

The two large copper pads are not in the right location. Care was not taken to verify the RAM slot footprint after part selection.

No video output

Built v0.4. Has no video output via the composite port.

Checking possibility that EMMC_DISABLE_N pin requires extra circuity to continue booting, although the Compute Module datasheet says this is only required under certain circumstances.

Have to check all pins on the RAM slot are correctly soldered.

Broken .sch File

Cannot open .sch file. I believe it needs repairs.

BOM is outdated

Release 5 uses different components than what was used previously, like the SD card socket.

Both Micro USB port footprints are incorrect

• No holes
• Incorrect orientation. 5V is currently connect to GND on the circuit.

Feature request: camera connectors

Hi, thanks for such a cool project! I've been trying to create a similar project on circuits.io, but haven't gotten this far (I don't have any prior experience about pcb designing). My motivation is to have a CM3 IO board lightweight enough for model aircraft use, with stereo camera support for 3D FPV (first person flying), utilizing wifibroadcast project.

IMO, the dual camera support really makes Raspberry Pi an unique platform, but unfortunately the foundation hasn't exposed the needed pins in their 'consumer' boards (Zero/A/B). The camera connectors wouldn't add much cost, as no expensive extra components are needed, aside the connectors and maybe few passives. (And one can always build the board without them, but it would be nice to have the routing.)

I'm creating this issue just for general interest. I'll try to implement this by myself once I get familiar with Kicad.

Currently Untested

This board is pending fabrication with a local supplier.

Release final BOM

Use HDMI output instead of Composite (Maybe?)

It'll be difficult to solder, but the RAM slot already is pretty difficult. This also removes the need for a 2.8V LDO.

Possibility of using a smaller inductor, with a lower current rating

SD Card require pull-ups

CMD and DATA lines D0-D3 of the slave SD Card should be pulled up by 50KOhm resistor even in 1-bit mode or SPI mode. The pullups of the slave cards should be connected even if they’re not connected to the host.

Adapted from: https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/peripherals/sd_pullup_requirements.html

Add power and usage LEDs

These would have been helpful for debugging. I currently have to use a multimeter to check if the unit is switched on. I could however just use the 3.3V pin on the GPIO slot for power LED.

Add more spacing between copper fills and pads

Not enough clearance between 5V and 3.3V nets

EN_jumper footprint is incorrect

Annular rings of Micro USB footprint too small

This issue occurred because OSH Park does not support square holes. When the holes were changed to circular, the annular ring was not checked.

Add silkscreen label for Reset and TV output

Poor decoupling

Possible poor decoupling on 2V8 and 1V8 rails. This will be tested when first prototype is delivered.
Additionally, using 1uF capacitor instead of 4.7uF for SD Card.

Some prices in BOM include VAT some don't

Prices shown on RS do not include VAT, but they do on Aliexpress.