Serial 7 Software Controlled 7-Way RS-232 Switch
Quick Start
(For clarity when the term "COM Port" is used, it refers to the Computer COM1 or COM2 etc. port, and the term Port1 or Port2 etc Refers to the RS-232 ports on the Serial Seven unit.)
Connections: (refer to the diagram for clarification)
Quick Start Connections. Both Computer are using 9600,8,N,1 no hardware handshaking.
The Serial 7 front
panel.
A simple three device hookup
Using multiple Serial 7 Switches it is possible to have up to 49 RS232 ports on one Computer COM port, all controlled by simple software commands, no hardware switching involved.
49 Way RS-232 Software Controlled Switch.
All 49 ports can have different Baud rates.
Power Source:
AC or DC supply of the correct voltage and current can be used, the Mini-DIN connector has a fully redundant set of pins to ensure a reliable connection.
As the unit accepts both
AC and DC there is no special plus or minus pin.
Supply Voltage
: AC 12 – 24 Volts 50-60HzDC 15 – 28 Volts
Supply current:
Depends on how many RS-232 devices are connected. Please make sure the power supply can deliver the initial switch on surge of about 350mA. A 12 Volt 500mA UL listed AC transformer is supplied with the unit. This transformer should not be used outdoors or in areas where lots of moisture is expected. When fully loaded with seven RS-232 devices it uses less that 2.5-Watts of power.
Main RS-232 Serial Cable:
A good quality serial cable should be used. If high Baud rates re used the main,keep the cable as short as possible, 6-12 feet high quality cable will operate well at 230,400 and115,200 Baud. A 9 pin to 9-pin cable with 1 to 1 connections is required for the Host to PC main serial connection.
1 to 1 straight through cable. Similar
ready-made cables are available for 9 pin to 25 pin. Please DO NOT use the 9 pin to 25 pin
adapters that seem to be everywhere as debris from previous Serial Mouse installations,
these adapters ARE not fully wired and will NOT work. If you do need a 9 pin to 25 pin
RS-232 adapter then please make sure it is fully wired, rule of thumb "If it works
with a Modem it will work with the Serial 7".
The Serial 7 PORT:
Consider each port of the Serial 7 to be an extension of the computers RS-232 COM Port connector, and has the following active pins.
Each port can be independently configured for
Baud Rate
Bit
Hand Shaking RTS/CTS hardware handshaking can be enabled or disabled for each port.
All settings are stored in Non-volatile EEPROM and are used each time the unit is powered on.
The Serial 7 User Interface:
The Serial 7 has a built in Text based user interface. With the limited space available for text data, some menus may be abbreviated.
The unit is shipped with a default Baud setting of 9600 Baud 8 bits for all port including the Host connections.
Connect a computer as described above, and run a communication or simple terminal program such as Qmodem or Pro Com, set the Baud rate to 9600 8 ,N,1
Apply power to the Serial 7
The Power On Screen
Lines 1 – 3 Copyright and Version Information.
Line 4 "Current Escape Character = +" This displays the character required to switch the Serial 7 into Command Mode (described in details later on)
Line 5 "Host RTS/CTS is Disabled" Hardware handshaking status.
Line 6 "Current Port 1" The currently active port on the Serial 7.
The Serial 7 has two modes, "Data Transfer Mode" (the default mode at power ON) and "Command Mode"
Command Mode:
This is the mode where setting are changed. To be able to send full binary data and at the same time have software control for settings, the Serial 7 uses a three character Escape Sequence similar to the Command Escape sequence used by modems.The default Escape Character is the +. A different Escape Character can be set and will be described in detail.
To Enter the Command Mode send three +++ in rapid succession and then wait at least 1second, and the command prompt will appear.
After sending +++ and
then a 1 or greater second pause, enters the Command Mode.
Data Transfer Mode:
Return to Data Transfer Mode by pressing the Enter Key
The Message confirm the Serial 7 is in
Data Transfer Mode.
Rule #1: When you are finished with Command Mode hit the Enter key and look for the message "Data Transfer Mode"
This ensures the Serial 7 is in Data Transfer Mode, and all settings are safe.
Help:
Press H and display the Help Screen.
Each command is described in detail.
As a reminder there is a small text representation of the Port and power connections of the Serial 7 front panel.
The B command:
Press B to set a different Host Baud rate
Select the Baud rate by pressing the respective character, if 115,200 Baud is required Press N
A reminder message is posted at the current Baud rate and then the new Baud rate is SET.
Please remember to change the Baud rate of your terminal program, as you will not be able to communicate with the Serial 7 until it has been changed. In this case change the terminal program Baud rate to 115,200 Baud. This setting is saved in nonvolatile EEPROM.
At this point the Serial 7 is still in Command Mode. You need to send the Enter Key character at the new Baud rate to ensure a return to Data Transfer Mode.
The F Command:
Press F and change the Hardware handshaking between the Serial 7 and the Host Computer.
Select by pressing E for Enable or D for Disable.
The choice was D and the message
"Disabled" confirms it.
This setting is saved in nonvolatile EEPROM.
The P Command:
Press P and Select a port 1 through 7
Select the port by pressing 1 2 3 4 5 6 or 7
The choice was 2 and is confirmed with the
message "Current Port 2"
This setting is saved in nonvolatile EEPROM, see the D Command for other options.
The D Command:
Each time the Serial 7 is power ON it must select a port, and using the D command it is possible to use the "last used port" or have it always use a fixed port. Press D
If a certain port should be the default port each
time the unit is powered on, simply select it by pressing 1 2 3 4 5 6 or 7
Example: Use Port 4 as the active Port each times
the Serial 7 is switched ON.
Or
Press L and the last used port before the unit
was switched off will be the active port when it is switched back on.
This setting is saved in nonvolatile EEPROM.
The R Command:
Press R and change the current port Baud rates setting.
Select the Baud rate by pressing the
respective character
Here 19200 is set by pressing I and the message
confirms it has been changed.
This setting is saved in nonvolatile EEPROM.
The T Command:
Press T and change the current port bit setting. The first line confirms the current port bit setting, which are 8.
Enter 7 or 8
The choice 7 and is confirmed by the 7
This setting is saved in nonvolatile EEPROM.
If the setting was correct simply press the Enter key and this message appears and no changes are made.
The J Command:
Press J and set the Hardware Handshaking for the current port.
Press E to Enable RTS/CTS handshaking or D to
disable it.
This setting is saved in nonvolatile EEPROM.
The choice was D and is confirmed by the message
"Disabled"
The M Command:
Press M and enable all message when in Command mode.
Confirmed by the message ON
This setting is saved in nonvolatile EEPROM.
The S Command:
Press S and no messages are displayed, except for critical error messages and the Help screen which is always available when in command mode.
Confirmed by the message OFF.
This setting is saved in nonvolatile EEPROM.
The V Command:
Press V and display all firmware version use din the Serial 7
The C Command:
Press C and enter a new Escape Character.
Press the key for the new Escape Character.
The New Escape character is the =
This setting is saved in nonvolatile EEPROM, and the next time the Serial 7 is powered ON if Message display is enabled it will be displayed as a reminder.
Current Escape Character = =
If a regular modem connected as a device to a Serial 7 Port, there may be a conflict, as most modems also use the +++ escape sequence. Remedy this by using a different Escape Character for the Serial 7.
FAQ or When Things Appear to Go Wrong!
Symptom:
There is no display at power on.Possible Causes:
1) Check the Power. Is there power?
2) Most likely the S for "Silent Mode" was selected last time the unit was used; this will cause no messages to be displayed.
3) High Baud Rate for the host connection, was incorrectly selected and therefore no data will be seen.
There are two remedies for this:
Reset to Default Procedure:
Switch OFF the Serial 7 power.
Use the Serial7.exe terminal program, or any other program that allows direct control of the RTS line.
Select a DOS session or Window, and run the Serial7.exe program. The command line arguments are as follows
Serial7 <COM port> <Baud rate>
Use Serial7 1 9600 for COM1 or Serial7 2 9600 for COM2
Then a screen similar to this (much reduced) will appear.
If there are errors, it could be the COM port you selected is being used by another application.
Free up the COM port and try again.
Once you have Serial7.exe running Press the Alt+R keys and look to the bottom left corner for RTS=ON.
"RTS=ON" is controlled by Alt+R which
toggles the RTS line On and Off.
With RTS=ON switch ON the Serial7 power and the following setting are reset to default values.
Symptom:
Data LossPossible causes:
Equal Baud Rate for Host and Connected Device and NO hardware handshaking. When a byte is received at the Host Connection, it takes time to process the byte before it is sent to Serial 7 Port.
Host Baud rate is faster than the connected device Baud rate and no handshaking is used.
Poor quality cables.
Extremely long cable length.
Possible Solutions:
Use hardware handshaking. When that is not practical, add a delay between each byte that is sent. In most communications programs this is called "pacing time". The exact amount of delay needed between each byte depends on several variables, such as:
This is just a short list of things that can cause data loss. A good starting point for pacing delay is 2 - 3 milliseconds. Some communications programs also allow a pacing delay every N bytes. Simply experiment and test to ensure your data is valid.
If there is no way to add pacing delay, then another solution is to run the Host at HALF the Baud rate of the Connected device.
Example:
This effectively puts a small (approximately 1 millisecond) delay between each character that the Host sends.
©Copyright 2000, Hans Wedemeyer, Houston, Texas, U.S.A. All Rights Reserved.
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