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I need to make an RS232 connection between the Cinterion TC65T (DCE) and another DCE device. In particular, from specifications the latter requires power supply on specific pins of the serial as follows:
+ Vcc on the 4 pin (DTR) (Vcc = 3: 12)
-Vcc on the 7 pin (RTS) (Vcc = 3: 12)
0Vcc on the 5 pin (GND)I state that through the TC65T it seems (unfortunately) it is not possible to set the voltage values of the DTR / RTS pins via software. I have successfully tested the connection between the two devices using two 9V batteries in series as follows: DTR-> [+ -] GND [+ -] <-RTS.
How can I make an efficient connection to a system of this type in steady state by minimizing the number of external power sources (and making it easy to maintain)?
Is it possible to exploit the additional outputs of the TC65T to obtain an additional power source useful for the case?
The first thing I can say is that the DTR and RTS pins cannot be driven, they are inputs and can only be read. You are probably referring to the CTS, DCD and DSR pins which are output pins as you can see from the attached schematic.
Serial criteria in no device can be programmed in voltage but can only be defined in the condition of active and inactive. And so I believe that yours unfortunately refers to the possibility of forcing its status. Possibility that on the TC65 modem it is possible through special java classes (See documentation).
As is known, an active RS232 signal has a positive voltage value, while an inactive signal has a negative voltage value with respect to GND. The voltage value depends from system to system and can be a value ranging from 3 to 15 volts.
From what has been said it is evident that by appropriately setting the modem serial output criteria you will be able to use the + Vcc and -Vcc voltages. Warning! these are RS232 signals therefore the output current of these signals is very low, it can only be used to power simple devices such as interface converters.
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