Help with custom SAMD21 Board

[hytralium]

Hi,
I have recently designed a custom SAMD21 Board, wich I am going to get preassembled, for a total of 5 boards for ~$100.

Since this is my first custom Arduino board it would be nice if anyone could look over the schematic and point out any wiring errors.

The whole thing meant to be a flight computer for a model rocket, so there is also a barometer, IMU and so-called "Pyro Channels".
This is a lot of money for me so if someone could help me, it would mean a lot to me. Thanks!
hytralium

BTW: I asked this question on the Arduino Discord Server and I was told to come here, so i hope this is the right place!

[CountChocula]

Howdy! Some semi-random feedback:

• It's a bit hard to follow the schematic—that's neither here nor there, of course, but there are plenty of resources if you want to learn how make your schematics more readable (which, in turns, makes it easier for others to give you their feedback).
• In the power section, R19 may have to be pretty beefy depending on how much current your circuit draws. 12W will go through it for every amp of current, so keep that in mind. (Perhaps consider using a fuse instead?).
• You should probably have an input cap on IC2, say 10µF ceramic. I would also bump C8 to 10µF.
• You're cascading U2 and IC2; probably OK, but do keep in mind that that's going to put additional stress on IC2—make sure that the total current draw is within spec.
• V_USB isn't going anywhere. If you're not using it, just add a no-connect to the USB input.
• You have multiple pull-up resistors on your SCL and SDA lines; this is redundant—once R1 and R2 pull the lines up to 3V3, you don't really need R3, R4, R5, and R7.
• There are no resistors on the green and blue lines of D1… are you sure that this is correct? I don't know the MPU very well, so perhaps it can sink the appropriate amount of current, but if not you may be overloading those pins.
• It's unclear how the pyro controls are meant to work; the PYx-CONT lines don't connect to anything. However, when you pull the PYROx lines up to 3V3, the PYROx-OUT lines are going to be shorted to ground. Make sure that that's okay (i.e.: not drawing too much current, etc.). Also, R10, R6, and R15 are pull-down resistors… why are they so low? As it is, they're going to draw nearly 10mA from the MPU's outputs when those go high).
• I'm not sure that your ICs are bypassed correctly. For example, I think there should be a 100nF cap between pin 13 of U3 and ground. It may be worth giving this a once-over.

I hope this helps. Cheers!


—CC