I got another one of these units and I have the exact same signal as shown in my original post here. I have the same signal on J2 pin 1. It's +/-5V and looks like it could be good data if the pulses were stretched out, or rather than going back to zero if the pulse hi/lo were connected...
But the data is still on the RX pin and is actually coming from one of the other uart's from the trimble 50 pin connector, pin 37.
from the website I linked:
36 -- UART3/Debug RxD
Voltage: 3.3V TTL
37 -- UART3/Debug TxD (57600 8N1) binary protocol, each 2 seconds bytes that seen as on "TOD EN" command are sent using this port. Voltage: 3.3V TTL. Transfer starts 70ms after PPS pulse. It's duration is 8ms.
So, that Tx routes to a Sipex converter and comes out to a cap. looking like proper data, but after the cap it's these spikes and is being routed back into the trimble RX pins, both the 50 pin header pin 34 and J5 P1, and that is where I would expect to send data from the PC to the Trimble board. ?
J5 Pin 2 and pin 34 (UART2 TxD HIGH VOLTAGE, ready for COM-port!) has -5V, about 200mV of jagged ripple.
I do not think this is a BG7TBL product, but the case is very similar or the same. I didn't think I was nuts but this sort of stuff makes me wonder.
I believe if I pull the caps from the the Sipex interface, the RS232 port connects properly to the 50-pin header uarts that it should, but there is still no data coming out of the Trimble board there. I also tried pressing the MACT button a few times and monitor during reboots and after a long sit with the ACT led blinking slow and fast.