In this video I look at updating the EMAX 12A ESCs with a direct connection to BLHeli via an Arduino Uno (as opposed to going via the flight control board). Initial reading of the supported SiLabs ESCs documents indicated it wasn't going to be straightforward. After some Googling I found the video below which shows step by step instructions how to do this.
The alternative would be just to buy one of the EMAX $10 programming cards which I guess is simple enough but then I'll never be able to do BLHeli firmware updates plus I like being able to use the BLHeli to check and set the ESC parameters.
After going through the process of soldering on a wire to each of the four ESCs and updating to the latest BLHeli, I found these particular ESCs don't support damped (damping?) light / active braking which is a bit of a bummer so I ordered four Little Bee ESCs instead. It would be interesting to compare between the two types of ESCs when it comes to flying but I'm not sure I'm up for the hassle of swapping out the ESCs.