Experimental Physics and
Industrial Control System

Mark Rivers <[email protected]> · Tue, 19 May 2015 22:00:34 +0000

Hi Eliot,

To follow-up, there are lots of reasons you could be getting "No reply from device".

- The USB-to-serial port could have a different pinout on pins 2&3 from the built-in serial port on your desktop.  You may need to swap pins 2&3, i.e. use a null-modem.  The easiest way to test this is with a voltmeter.  One device should be asserting pin 2 at -5V or more, and the other device should be asserting pin 3.  If they are both asserting pin 2 or pin 3 then you need to swap one end.  These voltages are relative to signal ground on pin 5, assuming you have a DB-9 connnector.

- The baud rate, data bits, parity, etc. could be wrong.  Set them in the startup script or with the asynSerialPortSettings medm screen.

- The permissions on /dev/ttyUSB0 could be wrong.  Setup udev as Andrew suggested.

- The device may not be being recognized at all, in which case you will need to use modprobe.

Serial is often a lot harder to get going than Ethernet, since there are more places for it to be set up incorrectly.

Mark

________________________________
From: [email protected] [[email protected]] on behalf of Specht, Eliot D. [[email protected]]
Sent: Tuesday, May 19, 2015 2:33 PM
To: [email protected]
Subject: USB-to-serial

I have a Eurotherm 2416 temperature controller which travels with me. I was using a desktop computer to run an EPICS IOC, but I realized this was foolish and am replacing it with a laptop. The desktop has a built-in serial port, while the laptop uses a USB-to-serial port. I'm running the same EPICS configuration with some updated modules, but the serial communications which worked on the desktop do not work on the laptop. I get errors with "No reply from device".

I'm hoping someone can explain the confusing results of my search of tech-talk. Some posts suggest that I just plug in the USB-to-serial and use the /dev/ttyUSB0 device which is automatically created. Others suggest that I need to use a command like "modprobe ftdi_sio vendor=0x67b product=0x2303", which gives the error "ftdi_sio: unknown parameter 'vendor' ".

Question: do I need to use the "modprobe ftdi_sio" command, and if so why is the 'vendor' parameter giving it trouble?

Details:

Eurotherm 2416 temperature controller with serial interface

base-3.15.1

asyn-4-26

stream-2-6a

sateco Eurotherm protocols from X.L. Wang

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System