Get
C-Kermit. Set up as follows, using values that match your application (speed,parity,stop-bits irrelevant for loopback tests):
Code:
set port /dev/ttyS0
set carrier-watch off
set handshake none
set parity none|odd|even
set stop-bits 1|2
set speed 300|600|1200|2400|4800|9600|19200|38400|57600|115200
connect
Put your loopback jumper on the port connector, usually between pins 2 & 3, and start typing. What you type should be echoed back to the terminal. If it doesn't work, suspect a cable or connector problem. Setting
carrier-watch to
off will eliminate the possibility that something is disabled until a favorable modem control line is asserted. Instead, you could loop the DTR pin back into either/both CTS & CD pins.
Using a DVM to monitor the Tx data will be futile, since the bit stream is very brief and transient. Using an oscilloscope should make it easy to see the data. What you can check is that the idle state of the Tx line is at an expected -3VDC to -12VDC while not transmitting. Failing to see this would again point to a cabling error.
Kermit is the best tool for serial communications on PCs IMHO, as it gives you very fine-grained control over all aspects of the configuration, as well as very and flexible terminal emulation. Another tool that I have played with a bit lately is
serlook, which is a serial port diagnostics, monitoring and logging utility.
Hope this helps.
--- rod.
Can't use serial port on Kubuntu 9.04 x86-64 bit.
