Thanks for the tip on the uart, but it doesn't work like that at this end using either my ch340g or my old baofeng serials, by connecting black/ground, all freezes, so cant ground the black, and with usb plugged in, of course, it is then also grounded, and freezes, the only way I can see any output at all is to remove the usb and ground. makes sense, since the tx provides the logic (and hence power), meaning only rx and tx are actually used. At least by my serials.
I also noticed my com in hardware settings does not have 921600, and when set in putty, it's not quite readable... working on it...
As for your pacman comment, Navin suggested updating adb which I did in windows, and was able to flash a boot.img, Which I could NOT do in fireiso. Off course, adb is not fastboot, but they both come together no? Most people in fact view fastboot as adb, albeit they are different programs, in the adb package... So fastboot in Fireiso needs updated, and after reading 63 pages of the unbrick thread, kamakiri also needs an update, maybe with a selection to choose from regarding what update you intend to flash in order to have the proper preloader/tk, as I noticed in the 7.6 stock rom, that the preloader is 0 bytes?
Please accept this as constructive critisism, seems all are getting blackscreened, yet no-one has a clue what actually causes it (yet), me, I'm looking, but its all so out of date I'm spending more time updating stuff I would never use if it was not for this damn firestick.
Edit, navin, what serial are you using, as in make?
try reading just by connecting tx to rx, it will work, dont add black, dont plug firestick into usb, tell me what you see
edit 2: I noticed in winscp that there is actually an option to connect to amazon devices using scp but it wants two keys which wouldf be amazons own login? Perhaps we need a different program to connect? In winscp file protocol, there is 'AmazonS3' The hostname is s3.amazonaws.com on 443, and wants access key id and secret key, is this connected to loging into the firestick uart?