Sponsored Content
Full Discussion: Serial Lines Explained
Top Forums UNIX for Dummies Questions & Answers Serial Lines Explained Post 302912179 by edfair on Wednesday 6th of August 2014 11:32:31 AM
Old 08-06-2014
Since most serial communications is via a UART this might help with the data transfer part:
Universal asynchronous receiver/transmitter - Wikipedia, the free encyclopedia

The UART voltage swings are between 0 and 5 volts. This signal is inverted and expanded to higher voltages by line drivers for transmission and inverted again and reduced to 0/5 swings by line receivers on the receiving end.

The transmitted signal starts degrading immediately and at higher transmission speeds it can be expected to be useless beyond 50 feet due to RC effects. (with a scope you would see rounding of what started as sharp shapes of voltage transitions)
 

We Also Found This Discussion For You

1. Ubuntu

Ubuntu 9.04 Serial application to telnet to serial device

Hello! I am working on an application which reads environmental instruments which have serial ports. The application requires a serial port to be present to talk to the device (i.e. /dev/ttyS0 ). In some instances the environmental devices will be 100's of yards away from the computer, so a... (5 Replies)
Discussion started by: mvona
5 Replies
MODBUS_RTU_SET_SERIA(3) 					 Libmodbus Manual					   MODBUS_RTU_SET_SERIA(3)

NAME
modbus_rtu_set_serial_mode - set the serial mode SYNOPSIS
int modbus_rtu_set_serial_mode(modbus_t *ctx); DESCRIPTION
The modbus_rtu_set_serial_mode() function shall set the selected serial mode: MODBUS_RTU_RS232 the serial line is set for RS232 communication. RS-232 (Recommended Standard 232) is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE (Data Terminal Equipment) and a DCE (Data Circuit-terminating Equipment). It is commonly used in computer serial ports MODBUS_RTU_RS485 the serial line is set for RS485 communication. EIA-485, also known as TIA/EIA-485 or RS-485, is a standard defining the electrical characteristics of drivers and receivers for use in balanced digital multipoint systems. This standard is widely used for communications in industrial automation because it can be used effectively over long distances and in electrically noisy environments. This function is only supported on Linux kernels 2.6.28 onwards. RETURN VALUE
The modbus_set_serial_mode() function shall return 0 if successful. Otherwise it shall return -1 and set errno to one of the values defined below. ERRORS
EINVAL The current libmodbus backend is not RTU. ENOTSUP The function is not supported on your platform. If the call to ioctl() fails, the error code of ioctl will be returned. AUTHORS
The libmodbus documentation was written by Stephane Raimbault <stephane.raimbault@gmail.com[1]> NOTES
1. stephane.raimbault@gmail.com mailto:stephane.raimbault@gmail.com libmodbus 3.0.3 05/26/2012 MODBUS_RTU_SET_SERIA(3)
All times are GMT -4. The time now is 07:07 PM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy