ErgoDox design question

[xmagusx]

My google-fu seems to be weak today. I know I've somewhere read the reason why in the MassDrop ErgoDox design the Teensy is wired to the board and a new USB header is then soldered to the board for the actual connection to the computer, but for the life of me I cannot remember why or where, nor have I been able to search up the information thus far.

So, for all knowledgeable folk here, could someone please re-enlighten me as to why the board is designed this way? Double internet thank you points if you can also link me the reference so that I can bookmark it for when I forget again. 

Thanks!

[regack]

Probably mostly spacing.  If you rotate the teensy 90deg to try to use the teensy's onboard USB, it would unnecessarily force the main PCB be a little 'taller' and subsequently the cases larger as well.  I imagine Dox had good luck with using the usb-jumper-to-pcb method in the original DoxKB and just used that same technique over again when putting together the ErgoDox.  If they went through discussion, it's probably buried somewhere in the ErgoDox thread.

[AKmalamute]

I remember reading that two of the wires had to be shorted if you routed a short cable instead of attaching to the PCB. Something like that the I2C bus needed more power than the teensy was willing to put out. Thus the wires go to the PCB first, power is drawn off, and the rest of it can be sent back down a cable to power up and operate the uC.

Not sure where to short it out to, or what would be underpowered.  But I do remember reading that. Once.

[Glod]

I remember reading that two of the wires had to be shorted if you routed a short cable instead of attaching to the PCB. Something like that the I2C bus needed more power than the teensy was willing to put out. Thus the wires go to the PCB first, power is drawn off, and the rest of it can be sent back down a cable to power up and operate the uC.

Not sure where to short it out to, or what would be underpowered.  But I do remember reading that. Once.

pretty sure this is correct

if you plug in a cable directly into the teensy the board will not work, bpiphany explained to me why it has to go to the board first before the teensy and that it wasn't something he intentionally wanted to do in his design. i forgot the explanation...

[plainbriny]

The PCB gerber file downloaded from ergodox.org doesn't seem to have this issue, maybe fixed already?
I attached the USB cable to teensy directly, and there is no need to connect Vcc.



However, I am not sure about the Massdrop version, maybe someone with Massdrop version of ErgoDox PCB can check this?

[Glod]

massdrop is using the earlier revision without holes for the cherry stabs so its possible yeah it could be what massdrop is using then, it doesnt work for me like that.

[Findecanor]

I have got one of Massdrop's PCB from their first run, with the USB connected directly to the Teensy.
I needed to solder an additional wire from the VCC pin on the Teensy to the +5V hole on the motherboard to provide power for the left half.

By the way, I think that the USB header on the motherboard is also more durable than the one on the Teensy itself because it is soldered through-hole.
If it breaks, it could be replaced. Replacing the surface-mounted header on the Teensy would be more difficult.

Maybe the Teensy could have been mounted on the underside of the PCB under the innermost columns, but that would have made case designs more difficult.

[xmagusx]

Thanks guys, from the sound of it, that aspect of the design is just a matter of getting power everywhere it needs to be (as well as providing a slightly sturdier connection point).

Appreciate the help!