SMS controlled Alarm System problem

[lloydi12345]

Hi, I am controlling an alarm through phone by using the serial communication feature of PIC16F877A. I am using ericsson t68i and everything works fine on the simulation and also on hyperterminal. Can you help me on the hardward part? I can't make the microcontroller and phone communicate to each other. I am just sending commands from the microcontroller to the phone but the phone can't accept it. I stripped the usb data cable that comes with the phone and it has 4 wires. Red, Blue, White and Black. I believe black is GND and red is Vcc. I tried supplying red wire with 4v connecting the gnd of the phone to the gnd of the board and tried connecting the blue wire to the microcontroller's TX, but it wont work. I tried also swapping blue and white. I tried shortening the wire that might cause the data loss but still no luck. I've based my project from this site: [SMS] Sony Ericsson PDU

Anyone tried this setup?

Regards,
lloydi

 

[Nigel Goodwin]

USB and serial are completely different things - you can't just remove the USB plug and connect it to a serial port.

 

[lloydi12345]

Thanks for the reply Nigel, but how can the guy connect the wires to the Arduino using only the TX and the GND? He was successful on his project.

 

[lloydi12345]

I opened the usb data cable and seen a little board. I realized that the 4 wires then inside the cable are converted signals from rs232 serial communication from the phone's pinouts. After googling the usb data cable's parts, I've seen Vcc, D+, D- and Gnd. The gnd is connected to the gnd pin of the phone but the Vcc on the usb data cable is just used to get 5v from the usb port to run the little board on the cable which converts the RS232 TTL signals to USB signals.

Can you suggest how I can convert D+ and D- signals back to rs232 serial communication mode? Is it possible without losing data sent?

 

[Nigel Goodwin]

I opened the usb data cable and seen a little board. I realized that the 4 wires then inside the cable are converted signals from rs232 serial communication from the phone's pinouts. After googling the usb data cable's parts, I've seen Vcc, D+, D- and Gnd. The gnd is connected to the gnd pin of the phone but the Vcc on the usb data cable is just used to get 5v from the usb port to run the little board on the cable which converts the RS232 TTL signals to USB signals.

Can you suggest how I can convert D+ and D- signals back to rs232 serial communication mode? Is it possible without losing data sent?

You would need a USB/serial converter - but why not just connect to the phone side of the existing PCB? - that converts serial to USB to feed a computer. if you connect before it, you've got serial.

 

[lloydi12345]

I've tried connecting it Nigel, but still something wrong. Do I have to do something on pins like DTS? from here Sony Ericsson R520, R310, R320, T28, T39, T68, T68i, R600, T610, T310 and others cell phones cable connector pinout and wiring @ pinouts.ru

 

[Nigel Goodwin]

Which wires were connected in the original lead?.

You also need to check the polarity of the required signals, it may be the opposite of what you're expecting.

 

[lloydi12345]

Oops the mistake was very simple, the cellphone was out of load that's why it can't send. Finally it was able to send messages. The connections used are only RX and GND of the phone. Now the problem is the receiving part. I want to read messages from the phone but the microcontroller can't read it. Any help with this last problem?

 

[Nigel Goodwin]

Oops the mistake was very simple, the cellphone was out of load that's why it can't send. Finally it was able to send messages. The connections used are only RX and GND of the phone. Now the problem is the receiving part. I want to read messages from the phone but the microcontroller can't read it. Any help with this last problem?

You need the TX line connected as well, and send the AT command to read the message.

 

[lloydi12345]

Yeah, of course I connected that, sorry i haven't indicated it on the previous post. I can't make the microcontroller read. Do I have to do something on other pins? like pin3 and pin 6 and other pins? They're just to many of pins to use.. I don't know if I'll hook them up on 5v or lower than 5v or even Gnd

 

[Nigel Goodwin]

Have you connected CTS and RTS?.

 

[lloydi12345]

No nigel, i didn't connected them. Where should I connect pin 2 (RTS) and pin 3 (CTS)? I really have no idea my friend.

 

[Nigel Goodwin]

Didn't the link you posted say they connected to ground?.

 

[lloydi12345]

No Nigel. He only used TX, RX and GND.

 

[Nigel Goodwin]

I was refering to this page you linked to:

Sony Ericsson R520, R310, R320, T28, T39, T68, T68i, R600, T610, T310 and others cell phones cable connector pinout and wiring @ pinouts.ru

 

[lloydi12345]

oh sorry, yeah I connected them to the ground. What else am I missing?

 

[Nigel Goodwin]

Nothing I'm aware of?.

 

[KeepItSimpleStupid]

Note this: The (Tx)&(Rx) are reverse for K300i model, you must connect CTS & DGND together on board and connect the common wire to CTS(Pin3) in phone connector. If your cable is working fine then dont change it.

There was also no mention of voltage levels. TTL? Are your levels relative to DGND? I'm not sure what CTS to common means.

Let me descrbe a sequence:

DTR - Terminal has power (depreciated in this case)
DSR - modem has power (depreciated in this case)
RTS - I want to make a call
CTS - dial tone is present
Tx
Rx
DGND

The way things used to work is with respect to the terminal (DTE device) connected to a modem (DCE). CE means consumer equipmet. The modem was the telco's equipment.

RTS and CTS were used in hardware flow control applications.