Charles- I worked for Maxim as an FAE and in strategic positions for a long time and have seen a lot of dodgy stuff. I’d be happy to take a look. I don’t think I could trouble shoot over email. These things tend to be grounding/return current issues, sometime easy to patch up but often requiring a rethinking for longer term solution. I could come by this weekend- let me know. I’m in Cary, near 55 and High House. Regards, John M. Wettroth E: j...@mindspring.com M: (919) 349-9875 H: (984) 329-5420 From: TriEmbed <triembed-boun...@triembed.org> On Behalf Of Charles West via TriEmbed Sent: Friday, March 22, 2024 10:27 PM To: Triangle Embedded Computing Interest Group <triembed@triembed.org> Subject: [TriEmbed] Integration trouble with motors + 5 volt buck + 3.3 volt linear Hello all, I don't think I will be able to have the robot ready to demo by the RARSFrest. There's an unexpected and frankly weird issue with the PCB that I am not sure how to resolve. Any advise would be appreciated. The GoodBot robot board has a STM32G0 microcontroller managing things, a GPS, 4 beefy hub motors and a Jetson Nano that it is powering. The basic setup is a 12.8 volt battery feeding the motors and a 5 volt buck regulator. This 5 volt regulator then feeds a 3.3 volt linear regulator that feeds the STM32 MCU and the GPS. If I run all 4 motors with the nano disconnected, then everything is fine. No issues with the MCU or the GPS. If I run the Jetson nano, however, I start running into problems (just got the physical setup to integrate, probably should have tested sooner). At various points in the boot sequence, the MCU seems to hang. It doesn't restart, but the program it is running seems to pause (brown out?) and then continue after a bit. I know it's not resetting because it would turn off the power to the nano if it did (also the led blink sequence continues).The same thing happens when I have the jetson start doing heavy computations. However, the real problem starts when I try to run a motor at the same time. The nano causes the MCU to stutter. This causes the motor to stutter, which seems to start affecting nano after a bit. Weirdly, my volt meter is measuring 3.3 volts the entire time with the MCU power supply. Any ideas on how to deal with this? Beefier 3.3v regulator? More capacitance near the MCU (tried sticking a electrolytic near one side of the MCU but it didn't seem to do much)? More motor or nano capacitance? Frankly, I am terrible at analog electronics. Any suggestions would be wonderful. It looks like a redesign is definitely going to be needed. Thanks, Charlie
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