Schematic/Layout Review

[ealayne2]

Schematic

• [x] Pin 4 of Teensy seems it should connect to GND, but is floating; this pin should be connected to GNDREF (if the pin is actually ground on the teensy)
• [x] Does each TOF sensor have a dedicated 2 pin shutdown and a separate dedicated 4 pin connector? I thought the stemma connected from one device to the next one in a chain?
• [x] Pin 4 of RPI probably should be shorted to 5V (connect Pin 2 and 5 together), similarly all the GND pins on the RPI should be connected to ground (not just a single one; this gets confusing as you typically want a "star" configuration for your grounds, but more importantly all the ground references should be connected together.
• [ ] Do you want to add a resistor to VREF on the motor drivers to add the option of including current limiting later?
• [x] The U4 voltage regulator should have both pins 2 and 3 connected to gnd (like the RPI/Teensy, all grounds/power need to be connected together)
• [x] Does the U4 voltage regulator enable by default, or do you need to pull the enable pin to make it work?
• [x] I'm not sure what BNO085 board you're using, just double check the CS/RST pins are okay and will work if they float

Layout

• [x] Double check ALL footprints are the right size and match up with the component you plan to put there (using the ruler tool in Kicad to measure between pins and verify it's what you expect
• [ ] I would suggest using 0805 or 1206 size components instead of 0603 (that size will be a bit difficult to solder without some practice)
• [x] Make sure the wires have enough space to bend for the encoders, I think those connections will be short so make sure the large connectors don't interfere and leave a large enough bending radius for the cables
• [x] The layout doesn't seem to have a huge number of crossing wires, but try to play around with it to get the lines to not cross too much to make routing easier & better (for signal integrity/noise/ease of debugging)

Routing

• [ ] Make sure to use large enough traces for the power (GND/12V/5V/3.3V); something like 20-25mils should be plenty for the 3.3V/5V, but 12V/GND may need larger at 30-50mils (also use a large ground plane to help with heat and larger copper for ground return
• [ ] Avoid vias when you can, moving/rotating components to avoid crossing the traces when possible (but don't go all around the board to avoid using a via)
• [ ] I'll review the routing some more once you have progress on it.

[ealayne2]

Routing

• [ ] Add filled zone for battery ground and GND_REF. As you add these, you'll want to add vias on the two nets to allow the ground to go between the top/bottom layers everywhere (otherwise you get empty spaces where a pin might not be connected to ground since there's no direct path to that area of the board due to other signals. See image below for an example of the top layer with a ground fill.
• [ ] Review layers you use to ensure there is a clear path from battery connector to each ground pin of the motor drivers, as well as minimizing the usage of vias. For this, I'd recommend looking at the board connections and swapping pins on the Teensy to make the wires cross the least
• [ ] Need larger traces for the motor pins, they should be larger than 10mils (15-20 mils minimum) otherwise they could heat up/burn up if the motor is running at too high of current for too long
• [ ] I'd highly recommend moving wires around your connectors as it's typically discouraged to route traces between other pins of other connectors (especially in this case you might have an issue with the distance between through holes and traces of other nets - a check your PCB fabricator will run and may tell you the board doesn't meet their requirements). One reason behind this is the accuracy of the solder mask vs the drilled hole, which might expose your traces if it's too close to the hole making it harder to solder (without shorting the wires together). Also as you're soldering, you have a chance to rip up the trace if you press too hard and slip while soldering the connector pin. To make routing possible while avoiding traces between connector pins, you can look into surface mount pin headers (see image below for an option for the encoder connectors, which should work with something like this, but double check this part number would work: https://www.digikey.com/en/products/detail/samtec-inc/TSM-106-01-L-SV-P-TR/7632814); this way you can route the signals underneath on the bottom layer directly underneath the connectors without needing to go between connector pins.
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