RS232 and RS232-C Serial
Legacy RS232 was designed for long distance communication of 300 meters or more. This was the standard for many years. The voltages are negative and positive. Typical range is -3 to -10 volts and +3 to +10 volts. This applies to both the TX and RX lines. Typical connections use a DB 9 connector, ground (pin 5) and pin 2 and pin 3 are normally used. Depending on the device (master or slave) pins 2 and 3 may need to be reversed using a 'cross-over' cable instead of a 'null-modem' cable.
RS232-C (this has become the replacement for Legacy RS232 and the manufacturer's do not alway indicate RS232-C in their product specification because it has become a standard over the past 15 years. The voltage range is 0 to +5 volts (TX and RX) and has less distance capability.
How to determine if you have RS232 or RS232-C!
With the RS232 device powered, measure the voltage from pin 2 to pin 5 (ground), and from pin 3 to pin 5 (ground). If either pin (2 or 3) is negative voltage (>= -3V) then you have RS232. If both pins show 0V (.1 volts or less) then you have RS232-C device.
The Brightsign:
BrightSign has recently adopted legacy RS232 (specifically XT1134) and maybe more. You can do the same voltage test but the BrightSign uses a 3.5mm stereo connector. The 'barrel' or 'sleve' is ground. The ring connection is the TX pin and the tip is the RX pin (from the BrightSign). With the BrightSign powered, measure the voltage from the barrel to the tip and then the ring. If either has negative voltage (> -3volts) the you have a legacy RS232 driver in the Brightsign. This connection may not compatible if you have an RS232-C device. Consult the manufacturer of your RS232 device for voltage specifications.
HMS Adapters:
RS232-C to True RS232
We have just added this adapter to our product line (June 22, 2024). This adapter converts the RS232-C of the BrightSign to RS232 legacy voltages. The signals from the BrightSign are inverted in order to correctly drive the RS232 driver chip. This is a 'level translater with invert'. No Processor so no baud to be concerned about. It just translates the voltage levels. This adapter also has jumper to select cross-over on 'null-modem' connection eliminating the need for a cross-over cable.-RS232C
RS232 to RS232C
If you have need to convert 'True' RS232 to RS232-C contact HMS Tech Support as there is no adapter available at this time!
Revised: 08/06/2024