M5Stack does not start with 5V pin of M-BUS

rin9147

I want to use the 5V pin of M-BUS to run m5stack. Because I want to use it on the PCB.

At first, the m5 was running on the PCB.
I had to remove and install the m5stack on the PCB several times.

I was just using the same program and suddenly it stopped running.

I thought that the m5stack was broken. However, with USB power supply, m5stack started.

I thought that one part of AXP192 was broken, but I could not determine it.

If anyone is using m5stack with power from 5Vpin, please let me know about this.

felmue

Hello @rin9147

when power is applied (either through USB or 5 V on M-BUS) the M5Core2 powers up and starts to run the program. When the M5.begin() command is executed by default the 5 V on M-BUS is switched from an input to be an output. That is the reason that by default M5Core2 runs from USB but keeps restarting when powered by 5 V on M-BUS.

If you want to power the M5Core2 through 5 V on M-BUS you need to modify the last parameter of M5.begin() from kMBusModeOutput to kMBusModeInput to avoid the switch.

Note: M5Stack (Fire, Base, Gray) have different hardware than M5Core2 and do not need to switch between input and output.

Thanks
Felix

rin9147

I set it up based on what you said and it works.

I noticed later that m5-docs had the same thing.
I'm glad you explained it in detail. Thanks.