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NebraLtd / nebra-lora-hardware

Hardware Files for a variety of Nebra LoRa Hardware
Creative Commons Attribution Share Alike 4.0 International
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Poor impedance matching on USB lines #5

Open Funkton opened 2 years ago

Funkton commented 2 years ago

According to USB specifications the data lines should be routed as 90ohm impendance differential and 45ohm single ended. On the indoor layout the lines are very poorly matched to 140 / 126ohm.

Staying within spec on 2 layer boards is practically impossible as it requires 3+mm traces.

The current layout has very high risk of having communication issues and/or running the drivers within hub/ethernet chipsets out of spec.

The board should be changed to a 4 layer construction where the top to second (GND) layer thickness can be selected for the proper impedance matching.

Additionally the board would benefit from proper ground plane stitching and good practice power supply design (it's really bad).

Nebra USB impedance

Check section 7 of the USB 2.0 spec. https://www.pjrc.com/teensy/beta/usb20.pdf

shawaj commented 2 years ago

@Funkton thanks for the input, much appreciated. Any chance you could ping a quick email to sales@nebra.com and let me know the ticket number?

shawaj commented 2 years ago

As with #6 this was designed by @ryanteck so will need his input on reasoning behind not following the USB spec properly

Andrewid commented 2 years ago

Is there a way to test whether this "broken LoRa module" is happening to me? If it's any help, my miner is sleepy-rose-porcupine

shawaj commented 2 years ago

The LoRa modules don't use USB so no