Archive for category: Frontpage Article

XLR switcher based on relay switches is one of the best solutions for applications requiring low audio distortion. The relay switches with gold plated contacts ensure high reliability. The bistable relays also sustain its state during device power off state. The low insertion loss of mechanical relay switches makes the LinkBone 1-to-15 switch perfect for of low level microphone signals.

This article is related with the following products:

• LinkBone 1-to-15 BNC switch
• LinkBone 1-to-15 Dual BNC switch
• LinkBone 1-to-15 XLR switch

The following picture shows an connection example with up to 15 signal sources and one receiver using XLR switcher.

The LinkBone XLR switcher routes signal bidirectionally. This means that the device can be used also for signal distribution. E.g from one source to multiple signal receivers as proposed in the following connection example:

XLR Switcher connection diagram

The following diagram shows the connection diagram of internal XLR switcher network. There are fifteen ports from A to O which can be connected to common node P. The user can configure state of each individual port via touch screen on device  front panel or remotely.

XLR Switcher remote control via Web interface

All LinkBone switches have an 10/100 Ethernet interface. The XLR switcher can be controlled remotely via Web interface shown on the following figure:

Additionally the device can be used for test automation by using an command line telnet interface. The list of commands supported by XLR switcher:

• off <port>          – turns off the specified port
• on <port>          – turns on the specified port
• reset                    – disconnects all ports
• mode <mode> – sets the mode of the switches

<mode> parameter can have two values:

single – only one port can be connected at the time. The device operates as a multiplexer.

multi – multiple connections are allowed to common port P.

This article describes how to control the device remotely: Coaxial switch command line script programming example

Summary: this article explains how to use LinkBone BNC switches in automated prototype hardware testing in development phase and production lines. The presented test automation environment is using the bed of nails tester fixture. The source code for remote instrument control and test script is included.

This article is related with the following products:

• LinkBone 1-to-15 BNC switch
• LinkBone 1-to-15 Dual BNC switch
• LinkBone 1-to-15 XLR switch

During the prototype development process engineers have to focus on the right quality of a product. This involves high number of hardware tests in different temperature profiles and often involving measurements done by hand. This process takes long time and involves human factor leading to errors. In case of production line testing, manual measurements take too much time. More efficient and reliable way of executing tests is by automated hardware test setup. The example of simple and low cost test environment is bed of nails with a signal multiplexer and oscilloscope.

Hardware testing with bed of nails tester fixture

Figure 1: Simple PCB used as bed of nails on the hardware prototype test place.

The figure 1 shows an bed of nails tester fixture made using a simple PCB with test probes. When placing the bed of nails tester on the tested prototype, nails are contacting the PCB test points. When having high number of test points it can be difficult to find an  measurement equipment having sufficient number of inputs. One option is to use the LinkBone BNC switch which can be used as a signal multiplexer/demultiplexer. In this approach only an oscilloscope with remote control interface and pass/fail automated test is needed. The bed of nails test pins are connected to the oscilloscope using a BNC switch remotely controlled via a automated test script.

The figure 2 shows the proposed automated hardware test setup. The BNC switch is routing signals from prototype test probes(or bed of nails tester), power supply and system clock from signal generator. The BNC switch and oscilloscope are controlled remotely via a test PC executing script or program. The remote control is done via 10/100 Ethrernet or RS-232 interfaces.

Figure 2:  Automated hardware testing setup with LinkBone BNC switch.

The following set of commands switches the oscilloscope input between A,B,C,D ports of LinkBone BNC switch. The device port connections are based on electromechanical switches that is why analog or digital signal can be routed bidirectionally. This allows to use the switch not only for probing the test points but also for signal distribution.

reset
mode single
on A
on B
on C
on D

The BNC switch from LinkBone can be controlled remotely via a set of text command. The following two articles explain how to control the switch from C++ or Python program level:

Control of BNC switches from C program via RS-232

Python programming example in automated hardware testing applications

Oscilloscope with Pass/fail test mask in hardware testing

Figure 3: Oscilloscope pass/fail test for prototype hardware testing.

The figure 3 shows the oscilloscope used in pass/fail signal test. The yellow plot represents the measured signal. The blue mask specifies the expected signal plot. When measured signal plot hits the signal mask the oscilloscope reports test as fail. Otherwise the test is reported as passed. User can specify the signal mask margin in case of high signal variation or jitter.

Figure 4: 10Mhz test signal connected directly to the oscilloscope and routed via a BNC switch.

The yellow signal plot on figure 4 represents 10Mhz signal routed via the LinkBone BNC switch to the oscilloscope. The blue plot shows the signal connected directly. In both cases the signal rise and fall times are 10ns. This illustrates the low signal distortion added by the BNC switch during hardware testing process.

References:

 Bed of nails tester (Wiki)

XLR switch and BNC switch with remote control via RS-232

Module can be used in Python 3.0.

//****************************************************//
//        Module: RS232linkbone.py                    //
//        Author: Marcin Debski                       //
//        XLR Switch and BNC Switch module for remote //
//        control via RS-232                          //
//        www.linkbone.com                            //
//****************************************************//
'''

import time
import serial

class rs232:
def __init__(self, port, baudrate, parity, stopbits, rtscts):
try:
ser = serial.Serial(
port=port,
baudrate=baudrate,
parity=parity,
stopbits=stopbits,
bytesize=serial.EIGHTBITS,
timeout=1,
rtscts=rtscts
)
print("Serial connection to LinkBone has been established!")
self.ser = ser
print(ser)
except:
print("Cannot connect via serial to LinkBone!")

# close serial connection
def close(self):
return self.ser.close()

# check if serial connection is already open
def isOpen(self):
return self.ser.isOpen()

# print information about status of the XLR switch and BNC switch
def getStatus(self):
self.ser.write(b'status\r')
time.sleep(1)
while 1:
status = self.ser.readline()
if status:
print(status.decode())
else:
break

# print list of available commands
def getHelp(self):
self.ser.write(b'help\r')
time.sleep(1)
while 1:
status = self.ser.readline()
if status:
print(status.decode())
else:
break

# print information about XLR switch and BNC switch device
def getInfo(self):
self.ser.write(b'info\r')
time.sleep(1)
while 1:
status = self.ser.readline()
if status:
print(status.decode())
else:
break

# send text command to LinkBone XLR switch and BNC Switch
def sendCommand(self, command):
self.ser.write(b''+str(command).encode()+'\r'.encode())
time.sleep(1)
while 1:
status = self.ser.readline()
if status:
print(status.decode())
else:
break

Summary: This article explains how LinkBone coaxial BNC switch can be used as a remote video multiplexer. Control of the device is possible via Web page from remote PC or via Infrared RC5 remote control. The RS-232 serial interface allows easy integration with other system components or standalone device operation. The LinkBone video multiplexer is a perfect choice for professional video processing applications and for industrial CCTV video multiplexing.

BNC switches from LinkBone can be used for video multiplexing in professional or industrial applications. Wide range of accepted voltage levels allow routing video and audio signals. Internal device signal lines have impedance matching to limit signal reflections. BNC input/output connectors are gold plated to limit resistance and ensure high contact reliability. Additionally internal signal lines have low capacitance to limit signal attenuation. The BNC video multiplexer can be mounted in 19-inch rack.

Video multiplexer example application

Figure 1: Multiplexing video signal from 15 cameras into one display.

Figure 1 shows example system with BNC switch used as a video multiplexer. Up to 15 signal sources can be connected to the device inputs. This can be a camera or any other signal source including audio. The selected input signals are multiplexed into one coaxial line. With Dual BNC switch version it is possible to multiplex up to 30 video sources into two coaxial signal lines. This allows to connect two video displays to fifteen CCTV cameras each. The control of the switch state is done via remote PC. The LinkBone BNC switches can be mounted in 19-inch rack to limit the installation space.

Figure 2: Infrared remote control of the LinkBone Video multiplexer BNC switch.

The video multiplexer can be controlled locally via an infrared remote control or a touch screen. The device accepts codes in RC5 standard. User can assign any specified port state configuration to the selected remote control button. The button assignment is done via a touch screen on the front panel.

Figure 3: Web interface for controlling switch state via 10/100Ethernet interface.

In applications where direct user access to the device is not possible a remote control over 10/100 Ethernet or RS-232 interfaces is possible. The telnet and http servers allow remote switch configuration. The video multiplexer switch can be also controlled via a web interface shown on figure 3. The http website displays a graphical representation of internal line switches. User can modify the port state by clicking on the status button.

Video multiplexer automatic switching using Arduino

The video multiplexer can be configured for automatic switching sequence execution. This can be done via a remote PC and a test script or program. More detailed instructions how to control the device via RS-232 text commands can be found in the following article:

 Coaxial switch with remote serial RS-232 interface programming example

The Video multiplexer can be controlled without a test PC. For remote control an Arduino or any other system/evaluation board with RS-232 interface can be used. Figure 4 shows an example application with Arduino controlling the video multiplexer. Before establishing a serial RS-232 connection the LinkBone BNC switch has to be configured via a touch screen on the front panel. User can configure the baudrate, parity and  stop bits.

Figure 4: Ardunio controlling the LinkBone video BNC multiplexer via RS-232 serial interface.

The Ardunio project page can be found at: https://www.arduino.cc/

The following code is used to switch between A, B and C video inputs. The video input source is changed every 5 seconds. The setup() function initializes the Arduino serial port to 9800 baudrate with 1 stop and no parity bits. In the next step ‘reset’ and ‘mode’ commands are sent to the BNC switch.

The main loop() function sends text command sequence for switching between specified ports. The delay time between port switching  can be adjusted by specifying different timing parameters in Sleep() function. The Serial.println() method sends text commands via serial RS-232 interface to the video multiplexer BNC switch.

//init the video multiplexer communication via serial RS-232
void setup()
{
//open serial port with 9600 baudrate, 1 stop bit, no parity
Serial.begin(9600);

//wait for the serial port to open
while (!Serial);

//reset/disable all inputs/outputs of the video multiplexer
Serial.println("reset");

//set the switching mode to multiplexer
Serial.println("mode single");
}

//main program loop
void loop()
{
//enable input A of video multiplexer BNC switch
Serial.println("on A");

//wait 5 seconds
delay(5000);

//enable input B of BNC multiplexer
Serial.println("on B");

//wait 5 seconds
delay(5000)

//enable input C of BNC multiplexer
Serial.println("on B");

//wait 5 seconds
delay(5000);
}

LinkBone

Summary: this article describes how to control LinkBone Coaxial switch with remote control via serial RS-232 interface. The complete code example in C++ with description is included.

This article is related with the following products:

• LinkBone 1-to-15 BNC switch
• LinkBone 1-to-15 Dual BNC switch
• LinkBone 1-to-15 XLR switch

The LinkBone Remote Coaxial BNC switch allows to connect different endpoints to the one common point. The device operation can be compared to the analog multiplexer forwarding signals from set of selected inputs/outputs into one signal line. Each link connection is bidirectional. Meaning that the device connected to the common port can be a signal source or receiver. The example of system with one common signal generator and several receivers is shown on figure 1. Read more