The scheduler device is not a USB device. the port on the side is just a standard TTL serial port for interfacing with the roomba's SCI. I took a few minutes last night to pin out the cable to confirm this... see the picture below (man i love MS Paint).
As you can see, there is a one to one correlation between the miniUSB connector and the miniDIN connector. Interestingly, the dual GND and Vcc pins on the roomba side are not tied together with the scheduler side.
As for PWR ON display, this is the result of applying power to the connector. What is interesting about this, however, is that if you apply power to the connector by hooking it up to the USB port of your computer, it will force a reset of the time. My guess is that during the initial USB data exchange that whatever the USB host is sending is really making the scheduler unhappy. if you just apply power to the connector it doesn't force you to reset the time, so its probably the USB host's communication that is bothering it. i might investigate this later if i have the time.
- miniUSB to miniDIN pin out
- roomba-usb connector pin out.JPG (12.19 KiB) Viewed 18491 times