I'm trying to get the RS485-Pi to output a signal that would be compatible with DMX. The UART part is fine, you can see on the picture below Signal 1 (yellow), which is UART out. Then you can see 2 (blue) and 3 (pink), which are the A & B output from RS485. Finally you can see M (red), which is the differential between 2 & 3 (or A & B). And as you can see, the voltage "direction" never changes, it's always negative or 0 (if I would do the math the opposite way, it would be between 0 and X, always positive).
(You cannot see the "2" marker because it's under "3")
Now let's look at a sample from a commercial DMX USB interface hooked to a Windows running PC:
This time, 2 & 3 are clearly opposed, and more importantly, when you look at M, you can see the signal varies between negative and positive.
How do I get such a result with the RS485 board?