2

I am currently using a Model A with a USB hub, but only have two USB devices connected to the hub, and want to reduce the system footprint.

Comparing my Model A (rev 2) with my Model B (rev 1) it looks like I should be able to get both of the ports I need by de-soldering the 1 port USB receptacle, sucking the solder out of the other filled in thru-holes and soldering in a 2 port USB receptacle:

CONN USB RTANG FMALE TYPE A PCB CONN USB A TYPE R/A DUAL T/H

Is this all I need to do, or are there other components I would need to add to get the second USB port to work?

6

Its not possible I am afraid.

The model A is missing the LAN/USB chip marked in the image. The BCM has 1 USB port, which on the Model B is connected to the LAN/USB Chip. This chip gives extra 2 USB ports that are connected via the PCB routes to the extra pins you wish to use. The other one is connected to the built in LAN interface (inside the IC), so in total 4.

In Model A, the red box is missing, so the USB trace goes to NC (No connect) but the alternative route is bridged(highlighted in yellow box) which goes directly the the single USB plug. If you look at the second USB trace it just goes to the LAN/USB IC, which is NC. In Model B, the yellow highlight box is not connected and the USB is connected to the HUB. And from there one trace joins back to the original USB trace and another isolated trace connected to the USB(Highlighted rectangle)

enter image description here

The Model A lacks this chip, and uses an alternative PCB route that is only connected to the one connector. The other one goes no where.

enter image description here

Alterantivly you can get your own IC and hack the Pi to have 7 ports (1 of which is connected to the existing port) using a Maxim 4999 IC. But soldering to this IC by hand is almost impossible by home DIY.

enter image description here

Another way would be to buy a mini USB hub, take it apart and attach it the Pi. Using a USB cable that goes into the HUB and then you get 4 more ports. But you may as well just use the HUB in its original state.

enter image description here

  • 1
    Thanks for a very comprehensive answer ppumkin, I didn't realise that chip was a Usb hub as well as Ethernet. I like the idea of stripping down the 4 port hub though, that might work. – Mark Booth Feb 2 '14 at 0:46
  • I forgot to check the Schematics to see if this was the solution :P Sorry, nice answer there. – Zeusking19-Code Feb 2 '14 at 8:41
1

It's not all you need to do.

There is an extra chip on the 'B' which is missing on the A; it is the square one directly behind the USB ports, and it contains:

  • 4-port USB hub
  • Ethernet interface (via USB)

In the 'B' those two USB connectors are wired to the ports on that hub, and the 'inboard' side of the hub is wired to the single USB port on the Broadcom SOC.

In the 'A' R-Pi, this chip is absent, and the single USB connector is wired directly to the Broadcom chip.

So, to upgrade to two USBs, you need to: - remove USB connector and replace with double connector - obtain and install the USB hub/ethernet combo chip - remove the jumpers connecting the port directly to the Broadcom chip

Sorry to be short on details - more info can be found on the R-Pi schematic - but the bottom line is it's probably not worth the hassle (and is definitely more than just adding a double connector).

0

From looking at the board, the pins to solder a two port are not there, there is only one set of four pins instead of the 8 required for the two port, so it is not possible.

Edit -> Looked again, it should be possible, but there may be unexplainable issues. Sorry, missed the thru-holes at the edge.

  • It is not possible :( – Piotr Kula Feb 1 '14 at 23:06

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.