The DTE dilemma

when a PC is connected to control a GSM Handphone, the PC is the DTE while the handphone is the DCE.
From wiki, Data terminal equipment (DTE) is an end instrument that converts user information into signals or reconverts received signals.

Therefore, the user information is entered through Hyper Terminal and is converted to control the modem.


If the PC is taken away and replaced by a microcontroller. Is the microcontroller now considered a DTE? I have read that there are such things as DTE-DTE connections.

Hope that someone can help me clarify

Thanks!

The microcontroller is used instead of the PC, so the microcontroller becomes the DTE.

The transmit line on the microcontroller will send data, which is received by the receive line on the GSM device.

thank you for your reply.

With the Microcontroller as the DTE, is it correct to say that RTS and CTS lines exist for both the DTE as well as the DCE (handphone),

basically is the RTS and CTS lines in the attached figure correctly named?

thanks!

RS232 Tutorial on Data Interface and cables
This website states that a Tx or Rx line is defined from the viewpoint of the DTE. meaning that the Microcontroller sends out data through the Tx line and the GSM Handphone receives data on the Tx line as well (DTE perspective)
If this is the case, should the RTS and CTS lines be treated equally so? If microcontroller raises RTS, the input at the handphone receiving the RTS signal is also named RTS in for instance a schematic.?

That can happen. The modules from Telit have the inputs as TX, (i.e. what you should connect to the TX line) which I find confusing.

It's rare to need RTS and CTS anyhow.

thanks again for your reply

It's rare to need RTS and CTS anyhow.

Click to expand...

so i assume RTS and CTS are only needed when the DCE communication line is not solely dedicated to a DTE but to multiple DTEs?

my handphone serial data cable (which I opened up) uses the Sipex RS-232 to TTL converter chip and all are SMT components.
So I presume that all outputs from the cable to the DTE are in RS-232 voltage. However, when I probed the circuit for continuity, none of the RTS and CTS lines actually connect to the the chip's RS-232 outputs but to passive components.

when i tested, in order for the handphone to communicate, the CTS pin of the db-9 end of the cable has to be given a Logic HIGH (5V) while the RTS pin gives out a constant 5V as well. If the RTS pin were directly from the RS-232 output of the chip, it means that the real RTS pin from the handphone would have sent out a Logic '0' to indicate that RTS is raised thus resulting in a positive logic at the output of the converter chip.
So my concluded question would be:
Do handphones Raise RTS @ 0V? thanks

btw the cable i use is the Sony Ericsson DRS-11 cable. Schematics on the internet differ from what actually is used in the cable which I opened. (Net schematics use the MAX3232)
Ericsson T-28, T28z, T28-world, T39, T39m, T60, T60d, T60lx, T61z, T68, A2218z, R300d, R300lx, R300z, R380-world and Sony Ericsson T68i, T100, T200, T300, T310, T600,T610, P800 cellular phones data and service cables scheme pinout and wiring @ pinout