Does anyone have experience making a serial RS 232 null modem? I have a cheapo usb to rs232 serial cable (HL-340/CH340), a female to female DB9 adapter and wired it up using:
2 -> 3 3 -> 2 4 -> 6 5 -> 5 6 -> 4 7 -> 8 8 -> 7
I also tried it with pins 2,3,5 only and pins 2,4,5,7,8 only. Have baud rate set to 115200 which corresponds other device.
I'm trying to fix a unix based set top box. It seemed to have wiped its bootloader for whatever reason; was installing usb wifi at the time. I can send it back but I'd like to fix it myself.
So the mjaority of the time it crashes putty. But I have managed to receive something using my cable hack but it is non human readable character garbage, From reading around (about null modem and tv boxes), it seems everything could be an issue; chipset, cheap usb adapter, F-F DB9 adapter (although I don't know how), my wiring or it could just by my set top box.
Has anyone come across this type of garbage in serial? Know what it might be a characteristic of? Maybe cheap usb decoding or unsupported chipset?
Its definitely a hack but I'm pretty sure the wiring is correct and all pins are making contact. I have received what looked like serial output (rolling text across screen) but again it was all garbage text.
Could it be flaky ground? Or having a problem with voltages like using 5v with a 3v device? Also make do you have you parity bits and stop bits set to good 8n1?
Good point on voltages. I will go over it with multimeter and check them out.
Not sure what you mean by this? Not that familiar with serial. From quick search I see its something to do with the way frames are built up. How can I affect this? I see something to do with it and baud rate?
