Fuses are a few special configuration bytes that are stored on the atmega328 microcontroller. Their role is to configure low level settings of the microcontroller such as the type of crystal oscillator connected to it, the brown-out detector level, the bootloader size etc.<\/p>\n
When you buy an OrangeRX or Wolfbox module, the fuses are preconfigured to certain values.<\/p>\n
It’s however possible to change their values under certain circumstances.\u00a0Just an FTDI cable isn’t sufficient to modify the fuses values, this can only be done with a programmer such as the USBasp programmer.<\/p>\n
There can be several reasons, but for ULRS project the most obvious one is to activate the brown-out detector on OrangeRX modules.<\/p>\n
The brown-out detector (BOD) is a simple feature of the microcontroller that will inactivate it whenever its supply voltage is below a configurable limit.<\/p>\n
This is advisable for any project, because if the microcontroller operates in undervoltage it can lead to unexpected behaviours : it can for example randomly jump to any memory location and execute the code.<\/p>\n
One consequence of this is that it can jump into the bootloader code and execute randomly sequences of code that will modify the flash memory. In this case the firmware itself can be corrupted and even after resetting the microcontroller and powering correctly it won’t work. Until the firmware is flashed again.<\/p>\n
Similar examples can be found in other projects (for example here).<\/p>\n
For this to happen the module supply voltage has to be very low, under 3.39V (remember that because of the switching regulator the supply voltage of the microcontroller is lower). This shouldn’t happen in normal use with the module connected directly to the battery, but it happened already to a user with an almost empty battery and full throttle.<\/p>\n
It’s not clear why Hobbyking doesn’t activate the BOD by default, but anyways for maximum safety it’s recommended to do it.<\/p>\n
Yes, because the Arduino Mini (ULRS Mini modules) have a factory setting of 4.3V BOD, which is fine as these boards run at 5V. So all the ULRS Mini modules based on arduino mini have already a good BOD.<\/p>\n
And for the Wolfbox modules this should still be checked.<\/p>\n