Hi,
I have created a PCB on which Arduino Pro Mini is installed.
Arduino is powered externally via the VCC pin at about 3.0V and everything works fine. Sometimes, however, when the Arduino is turned on it enters the bootloop with the red LED flashing.The only way to fix is to turn off the power. If it often works, I don't think the problem is too low voltage. Any solution?
I also tried not to load the sketch but the problem is the same. So I'm sure the problem isn't in the code.
What is the clock frequency of you Pro mini? If 8Mhz it should be good, if 16 Mhz it will have issues at 3V.
You were asked not what board you have, but what is the frequency of your quartz resonator.
I chose for 3.3V 8MHz version
Didn't choose.
What kind of quartz have you installed on the board and soldered?
OK so the board should work at lower voltage.
The power is coming from another device. This device is powered on by an Usb connection (input 5V, output 3V).
If Arduino is in bootloop, I pull the connector off the device that powers it and plug it back in
About the PCB, I would prefer to keep everything private if it is not extremely necessary. In any case, it is made up of extremely simple components. I'm sure the motherboard isn't the problem because I also tried to power Arduino directly.
Could it be a problem in the bootloader? I tried to load MiniCore with Optiboot but the situation doesn't change
Given the information I have I am of the opinion the Vin = 3V is not providing the full 3V all the time. It could be "sagging" during bootup.
Do you have the wdt (watchdog timer) running?
The power is coming from another device.
Does this other device have the required capacitors?
I believe so too, but it shouldn't go into bootloop. When the power goes 3V it should restart by itself.
Do you have the wdt (watchdog timer) running?
I don't know the watchdog so I would say no.
Does this other device have the required capacitors?
The other device is a steering wheel for the computer. I think it have all needed components.
I don't really want to imagine a power supply that causes a significant voltage drop with only uC current consumption...
If uC's BOR (Brownout Reset) is enabled, it is quite possible that it will boot and repeat the BOR.
How can I check or how can I set it? If I remember correctly with Optiboot I setted it at 2.7V.
It is BOD or are we talking about two different things?
If you want to know the location of the error, unplug the Pro Mini from the motherboard, supply good 3.3V power and check.
If you installed the Pro Mini on the motherboard, then everything that you connected to its pin is important.
If your motherboard with multiple resistors is secret, it will be difficult for you to get useful advice here.
Sometimes it helps to connect a cap of 100nF~470nF to the reset pin of the uC. This gives the PSU to ramp up. This usually only takes a millisecond or so, but that will be plenty long enough for the uC to already get started and it may get into trouble if the power isn't stable at that point. By keeping reset low a little longer you prevent this from happening.
You are likely operating the Pro Mini in a gray power area. 0 = Off and 3 = on but in the middle things are not always so black and white.
I suggest you add a 100µF or so capacitor on the power line to the Pro Mini.
I already did it on my pcb
Was the 100µF there when you had the bootloader looping?
Yes but I also tried without capacitor
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