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I am programming an application in VB.net (2010) to communicate with a serial device. I tested the device with Advanced Serial Port Monitor 4.3.9 (ASP) manual mode and all the commands work with the expected responses. My COM port settings are 4800, Odd, 1 stop bit, 7 data bits.

In my app I see a command being written to the device using ASP (spy mode). I also see the display of the device change indicating that it reacted to the command. At this point, it is supposed to send a response but I never see it in ASP or in the receive buffer of the port.

Does this have anything to do with RTS or DTR, etc.? Any other ideas?

Thank you!

Hello,

Did you compare your commands in the manual and spy modes in the HEX window?

FYI: in the spy mode our software can display the received data only if your application received it.

I did run the spy mode in hex. The comand sent "05 0D" which queries the device for its presence. In ASP manual mode I see a response from the device. In spy mode I see the command and the device appears to be reacting to the command based on its LCD display, but no response is received.

Per the device's manual: "The serial data format is full duplex (simultaneously transmit and receive), 1 start bit, 7 data bits, one odd parity bit, and one stop bit at 4800 bits per second. All data transmitted will consist of characters from the standard ASCII character set."

One thing I noticed was when I run ASP in spy mode then open the port from my code I get a bunch of stuff appearing in red letters. I copied it below. No such information appears when running in ASP manual mode. Is there something I need to do to configure the port in my application other than setting the baud, parity, etc?

Any help you could render is greatly appreciated!

COM is open
Baud rate 4800
RTS off
DTR off
Data bits=7, Stop bits=1, Parity=Odd
Set chars: Eof=0x1A, Error=0x3F, Break=0x3F, Event=0x1A, Xon=0x11, Xoff=0x13
Handflow: ControlHandShake=(), FlowReplace=(ERROR_CHAR), XonLimit=1024, XoffLimit=1024
Baud rate 4800
RTS off
DTR off
Data bits=7, Stop bits=1, Parity=Odd
Set chars: Eof=0x1A, Error=0x3F, Break=0x3F, Event=0x1A, Xon=0x11, Xoff=0x13
Handflow: ControlHandShake=(), FlowReplace=(ERROR_CHAR), XonLimit=1024, XoffLimit=1024
DTR off
Set timeouts: ReadInterval=-1, ReadTotalTimeoutMultiplier=-1, ReadTotalTimeoutConstant=-2, WriteTotalTimeoutMultiplier=0, WriteTotalTimeoutConstant=0
In/out queue size 4096/2048

1. What do you see in the HEX window when you send the command from ASPM? Is it possible these commands are different?

2. In your code try to set the DTR signal to the active state.