5270 third uart port

[BillC]

Hi, I am not sure if this should be a hardware or software problem, so thought I would start here.

I wish to use the third uart port on the 5270 module on a MOD-DEV-70 Carrier Board and want to find out which pins the signals are bought out to, just the TXD and RXD, I dont need any other control signals.

I looked through the supplied docs but couldnt find anywhere that this was specified.

Can anyone please supply the information or point me to the correct manual.

Thanks, Bill

[Ridgeglider]

Pin J2[44] is Uart2 Tx from Mod5270,
Pin J2[41] is Uart2 Rx to Mod5270 (even though the schematic labels them CANTX and CANRX).
Note: the Uart2 Tx and Rx pins are LOGIC level and NOT RS-232 level.
Unlike Com0 and 1, there are no serial level shifters for Com2 on the DEV 70 board.

I often use these boards and some jumper leads for proto level shifting:
http://www.acroname.com/robotics/parts/ ... -CONN.html

See the file C:\Nburn\MOD5270\include\pinconstant.h for a description of the pin functions, along with http://www.netburner.com/downloads/mod5 ... O-R1p1.pdf

Also see the OpenSerial() function in the C:\Nburn\docs\NetBurnerRuntimeLibrary\NetBurnerRuntimeLibraries.pdf

I suggest calling SerialClose() for the port before calling OpenSerial().

[BillC]

Thanks Ridgeglider thats exactly what I needed, now I know why I couldnt find the signals on the schematic, also thanks for the link to the level shifter board, I am not in the US but have seen similar items on Ebay in the UK. In this case I will wire up my own as I also need to add another 2 async ports using an I2C dual port uart so a fair bit of breadboarding will be needed.

Thanks again, Bill

[BillC]

Hi again.

I am now considering interfacing the 5270 third uart port to a modem that can support Voice modes, and have found a MultiTech 5V embedded voice modem module (MT5656SMI), can anyone tell me if the 5270 third uart TXd and RXD signals can interface directly to the modem module or will I need to use level convertors. The electrical spec for the modem signals are

Digital Inputs
Input High - Min 2V
Input Low - Max 0.8V

Digital Outputs
Output High - Min 2.4V
Output Low - Max 0.5V
Current Drive - 15mA
Digital Input Capacitance - 5pf.

Thanks for any help that you can provide.


Bill

[Chris Ruff]

The multiTech modems are designed to connect directly to "TTL" signal levels. So you don't need a level-shifter (like a MAX232) in there at all. Just connect the 5270 Tx line to the multitech Rx line and vice-versa.

Make sure that you completely understand which way the data is travelling on the lines. Sometimes Tx is the line that drives, sometimes someone calls a line Tx that is supposed to be connected to the Tx line. real helpful. the 5270 driver line (Tx) needs to connect to the multiTech input receiving line (Rx). then connect the other two lines together in the other direction.

Chris

[BillC]

Hi Chris, thanks for your prompt reply, yes I will be aware to get the the signal directions right (I have been caught out on that before ! ), I just wasnt sure if I needed a 3 to 5 v level convertor as the modem module uses a 5 v supply and the 5270 is 3V.

Thanks, Bill

[BillC]

Hi again

I am still unclear if I need to use a 3.3V to 5V level convertor between the 5270 signals and my 5V modem module.

Does anyone know the answer please.

Thanks, Bill

[Chris Ruff]

For the line going to your modem from the processor, no. The threshold is set at 2 volts so it will work direct connect.

for the line coming from your modem, have the modem drive a 330 ohm resistor and use a diode to clamp the processor end of the resistor to 3.3 volts (cathode to the resistor and anode to 3.3 volts)



Chris

[Chris Ruff]

oops! anode to resistor and cathode to 3.3 volts!

[BillC]

Hi Chris, thanks again for another prompt reply, you are a star.

OK, I think I should have enough breadboard space for a resistor and a diode, I was going to use a 74cx245 buffer if needed but was not looking forward to soldering the TTSOP package on to a DIP adaptor, so you have made life much easier.

Thanks again, Bill