Valery is the expert here, so you should follow his recommendations, but I believe you will still need the FTDI Programming Cable if all you want is to upload a newer version of the firmware. However, "if" your JuiceBox was built with an older version of F/W, you just can't skip to a newer version unless your hardware (PCB version) is KNOWN TO SUPPORT IT. There are certain dependencies in the hardware, that ONLY the same version of firmware supports properly.
For example, I started out with V8.7.9 firmware with a V8.7 PCB. I have since uploaded to F/W V8.7.13b. The latter has various modifications of my own choosing to support a slightly larger display module, but my modified firmware is still based on V8.7.9 (compatible with the original uLCD) and original V8.7.x PCB. Because my PCB is still the same, later version(s) of firmware (e.g. V8.9.1) would NOT necessarily be compatible with my existing hardware, and for sure it wouldn't be 100% compatible with my new display.
Sometimes, new versions of F/W can be made "compatible" with respect to older H/W, but eMW's verification "testing" probably was only done with the latest hardware, so mismatching versions of H/W and F/W would generally not be advisable.
Last edited by dsinned
on Sat Oct 25, 2014 9:14 am, edited 1 time in total.