[wetwillyskate]

I searched all of the E90+ forums i know for a pinout of this "JB BMS USB Cable" and i couldn't find a thing. So i was stuck buying it for $35.

Step 1) Buy everything you need from a site like Mouser or Digikey

buy a TTL RS232 cable (5V) for $20

http://www.mouser.com/ProductDetail/...52bZBasxjZs%3d

buy a DB9 Male (pins not sockets) for $0.43.
If you're like me you have these in your parts bins already

buy a clamshell for $0.65 (or buy a nicer metal one for $2)

http://www.mouser.com/ProductDetail/...RQEfBJiA%3d%3d

Step 2) solder the black wire to pin 5 of the DB9 Male

Step 3) solder the red wire to pin 3 of the DB9 Male

Step 4) solder the yellow wire to pin 1 of the DB9 Male

Step 5) assemble clam-shell and you're done!

I know this only saves $10-$15, but the principle of the matter is that you shouldn't charge more for something by playing on the ignorance of your customers.

[teamyamaha91]

Correct me if I am wrong, but would that only be vcc, gnd, and rx? How would we transmit without the TX line?

I am also trying to make my own cable and was able to trace on the jb4 pin 3 as RX, pin 1 as TX, and pin 9 as an unknown for me. I was not able to find any other pins that actually go anywhere on the jb4 board.

[Chocolate Apocalypse]

Looks like yellow(1), orange(3) then black(5) here:

http://www.e90post.com/forums/showthread.php?t=359363

[Chocolate Apocalypse]

I can attest to the yellow, orange and black wires doing the trick. Just upgraded my BMS CAN tool with my homemade serial to USB cord

[Maniac0908]

Does anyone know which wires are which? Im guessing black is ground. But which is tx and rx?

[Grootkop]

The cable is a USB to serial converter TTL 5 vdc
The pictures are simple enough to follow black is ground negative
and the orange and yellow are transmit and receive

[Pinscher]

So BMS, says not to use store bought cables.

Should I be DIYing this myself if they say not to or are they just trying to get big $ on cables by re ordering the pins?

[d.candita]

I just tried it out and it worked for me. I bought a DB9 D-Sub Male adapter and connected everything like the Picture above.

I also bought a USB cable that has 6 Pins (not sure the name of it)

Connected everything together and changed some setting on jb4. Works perfectly fine!