USB Host on the Jornada 720

My attempt to get USB host working on the Jornada 720 with Linux. Wiring is done according to the SA-1111 development module schematics sa1111_development_module_schematics.pdf

It is now “fully” working! The only downside: we have to downclock the CPU to 192 MHz. I have to investigate what is the root cause here. Maybe it is a clock issue in the kernel/driver or some power or EMI issue.

You can do that with the utility!

Wiring / Schematics:

We need to access 4 pins from the SA-1111 Chip.

SA-1111 mBGA Mechanical Drawing

  • - USB_PLUS (green - First wire of USB data link pair): H3
  • - USB_MINUS (white - Second wire of USB data link pair): G1
  • - USB_PWRCNTL (red - Output signal enabling power to the usb port): H4
  • - USB_PWR_SENSE (blue - Input signal indicating overcurrent condition - active low): K5

Luckily these are als present as vias / pads on the mainboard. You have to disassemble the Jornada and take the mainboard out in order to do this modifications! I used fine insulated copper wires to do that.

To access USB_PLUS (green) and USB_MINUS (white) you have to remove the ROM/RAM board and solder two wires into place as shown in the picture. Remove the two SMD resistors from the pads!

USB+ and USB- on the mainboard

For accessing USB_PWRCNTL (red) and USB_PWR_SENSE (blue) you need to desolder the metal shield of the PCMCIA slot from the mainbord. The two pads underneath it. You also have to replace the SMD resistor (yellow circle) with a 10kOhm resistor!

USB_PWRCNTL (red) and USB_PWR_SENSE (blue) on the mainboard

Now you have everything to wire up a USB Current-Limited Switch and a USB port! I used a MAX1607 for this. Wiring is done as described in the “Intel® StrongARM® SA-1111 Development Module Schematics” on page 12. Since my J710 doesnt have a dial-up modem I put everything in the place which normaly holds the modem PCB. The USB plug is mounted instead of the RJ11 jack.

I took +5V and GND from a nearby capacitor as seen on the last picture. That may not be ideal but it is the output from the DC-DC and should work for first tests!

Intel® StrongARM® SA-1111 Development Module Schematics


Here is the old archived Jlime documentation about USB Host on the Jornada 720: