Fuse Bits set to BOD?

[duckythescientist]

How are the fuse bits set for the Digispark? I have a 3v3 regulator (MAX604) on a breakout board, and the Digispark keeps resetting itself when I plug the board in (or randomly if the board is already plugged in). I'm going to check to see if I can measure much of a voltage drop, but it would be nice to know if I am triggering the brownout detection.

[duckythescientist]

As measured without my secondary regulator:
Vusb=5.1
VdropDiode = 0.36
//VdropRegulator = 0.8 //a useless number since the regulator isn\'t powering anything
Vtiny85=4.74

with secondary regulator
Vtiny = 4.56
V3.3 = 3.28 //within spec of MAX604

So the attiny is powered through a schottky diode from Vusb. This is connected to the output terminal of the 78M05 regulator (I\'m hoping it has internal reverse voltage protection).

ATMEL gives the minimum safe operating voltage for 16.5MHz to be 3.87V which is within range of what the chip is getting. Brownout detection has a setting for 4.3V (4.1 to 4.5), and a spike could easily push it over the brownout limit.

I\'m going to bypass the schottky diode and see what happens. I\'m pretty sure its only purpose is to protect the USB host if the Digispark is being powered externally. I\'ll just make sure not to do that with this one.

[duckythescientist]

Now without the secondary regulator, Vtiny = 5.09
with the secondary reg, Vtiny = 5.09

I\'m still getting resets, and I\'m not sure why.

[digistump]

You can apply the power directly to the 5v pin to bypass the diode. It is designed to be stable at 4.5v-5.5v so your supply should be in that range

Here are the fuse settings:  lfuse:0xe1 efuse:0xfe hfuse:0x5d

and yes the only purpose for the schottky is to protect the USB host

[duckythescientist]

Hrm... that\'s a 2.7V brownout. I guess I\'ll just have to explore other possibilities for problems.