IR100
PCB
The Barracuda PCB plugs into a motherboard within the IR100. The following image is a composite, showing both the top and bottom PCB layers.
Connectors
There are three edge connectors on the Barracuda board (J1, J2 and J3). The pin naming in the image below has been extracted from the IR100 motherboard silk screen.
File:Barracuda-pinout.png Pinouts of Barracuda connectors |
USB
There is something odd about the way the USB connection has been made. The IR100 connects the USB D+ and D- with 22R series resistors, and also, each pin has a 15K resistor, which is terminated somewhere on the Barracuda PCB.
For a bus master, the two 15K resistors should be pull-downs - full stop!
For a bus slave, one or both of these resistors should be missing.
It is possible that this single port can be configured as either a master or a slave (Pin M10 is DP1/PDP0, Pin N11 is DN1/PDN0 - i.e. DP1&DN1 are the Host Functions and PDP0&PDN0 are the Slave Functions, sharing the same pins).
From the source code reciva_usb.c file, it suggests that the driver powers up with the USB interface in slave mode - this should be detectable by monitoring the two 15K termination pins and the USB VCC during power-up.
Some time during boot, the USB VCC should appear, and the 15K pull-downs will be connected. The question is how to convince the board that the USB should remain a slave, and not make the transition to master ... things to try ...
- Remove USB device from radio before power-on. Then measure USB VCC and status of pull-ups/downs.
- Connect the USB VCC to 5V (via an R to be safe) during power-up.
- Connect two 15K pull-downs to the D+ and D- pins during power-up.
