nrf52840 pi hat

[sentinel_infinitus]

hi all

i have been working on a raspberry pi hat design and i would like feedback on it's design

this is the link to the github repo and i do update it regularly  https://github.com/sentinelinfinitus/nrf52840-pi-sheild

fair warning i used kicad and for some parts were added using mousers library loader

if you see some things i am doing wrong or have any suggestions on how to do some things better please let me know

[Andreas]

Hi,

 

This looks quite good. As you say, the reference design uses blind/micro vias in the inner-row pins. This is to make sure the SoC has good ground in that the center pad is connected to a solid plane in either inner or bottom layers. By using through hole vias this will no longer be the case, the vias wil break up the ground plane which might keep certain sensitive parts in the SoC from operating as specified.

There are some ways to workaround this, by not using all the inner-row pins there will be better grounding overall. In addition there are some pins that you easily can route outside through the top layer. The ANT pin and the VSS_PA pin should also not have vias in them.

I have also seen examples of designs where the inner-row pins have been routed out in the top layer between the pads of the outer-row pins. This obviously will depend on the capabilities of your PCB supplier and EMS. You might also have to make the pads of the outer-row pins a little smaller.

 

Best regards,

Andras

[sentinel_infinitus]

hi Andreas

i did fix the part so that there were no vias under any pads

also i have created the basic hat and even exported it's gerber files there in the hat\basic hat folder

would you mind taking a look at it to see if the pcb is good

something to make note of is hat you can do micro vias under pads in kicad by setting up a micro via off to the side and dragging it under the pad you want it under if you get a question about it in the future

[Andreas]

Hi,

 

Thanks for exporting gerbers. The footprint looks better now, you can probably proceed with placing the components. Again, I strongly recommend that you replicate the reference design as closely as possible, especially the RF part. Deviations to distances between components, pins, pads, ground pour etc. all affect the performance to some extent, by being 'nitpicky' you increase the likelihood that you get a well performing board and thus do not have to do another spin or make any janky fixes to make it better.

 

Best regards,

Andreas