Hi all,
created a separate thread for the Televideo 910 terminal discussion.
Connected a terminal up to it this afternoon, settings are:
19200, 8, N, 1
plug is DB25 female but wired as DTE meaning
pin 2 is TxD (out)
pin 3 is RxD (in)
pin 4 is RTS (out)
pin 7 is signal ground.
If anyone needs a loaner USB/RS232 cable then I have one. I also have a DB9/25 adapter.
The cable exposes a female DB9 (DB25 with the adapter attached).
the thing is that the level maybe too high coming out on the televideo 910 , and in discussions with Stephen, we had to get a rs232 chip that will convert from 15v +_ to 3.3v for the uart pins on the pi …and directly drive anything from there … i have to find the discussion with Stephen to find the chip.
I am not clear here. I thought the pi will attach to the USB side and the tv910 to the RS232. If the TV910 expects 3.3v (unusual on a DB connector) then you need a USB/TTL cable/adapter. These are either 3.3v or 5v and some are voltage selectable.
Then again maybe I got the wrong end of the issue…
Gents, the tv910 port is standard rs232. That means +/- 12 volt levels.
@eyal is correct, an USB/rs232 adapter cable has the correct level drivers to match the rs232 standards.
@crashman39 is not talking about using the pi USB port, he is talking about using Pi gpio pins configured for uart operation. This will require a level shifter chip to interface the +/- 12 signals to 3.3 logic levels.
We attached a USB/RS232 + DB9/25 to the TV910. Locally the 910 does not respond to keystrokes (no echo?). From the PC (putty) no reaction at all either. Based on the switches say 9600 baud.
Check your cables, I tested it 6 months back and it was fine. I believe the pin out is non-standard, plug is male, I.e. gendered for DTE but wired as DCE.
Tested two cables. However, maybe a crossover cable is required? It will then not be the correct gender as a standard xo cable.
Better still, I have a special DB25 M/F adapter where the wiring between the two sides is jumpered rather than fixed. Should make this work.
And this afternoon I made a nicer cable mostly because I somehow ripped a pad off my frankencable and couldn’t fix it.
@sjdavies, noob serial terminal question: is the four pins enough? It certainly mostly works with only the four pins. (Wondering where the weird extra characters might be coming from).
After fixing the pinout mistakes I had made with my new cable, all is working! and the weird extra characters have gone - I suspect it was a short or something with my previous frankencable, and not the keyboard having been cleaned now that has fixed it.