Help interfacing a 16f876A with a USB GSM mobile

[motofreek]

Hi,
Does anyone know of a circuit that I can use to interface the UART pins of my PIC16876A to a GSM mobile phone that uses a mini USB jack ?

[I am able to communicate perfectly well with the PIC and the PC using an RS 232 DC to DC converter I built]

But when I try connecting the UART's Tx and Rx pins to my phone's D- and D+ (usb) and cant communicate at all !

Any help would be great...:?:

 

[hanif]

Hi,
check this topic , this may be usefull for you.

GSM modem with PIC 16F877A

 

[bobcat1]

Hi

You Can't connect UART to USB and expect it to work!, it is two different methods of communication

To access a USB slave (like a cellphone) you will need to connect it to a USB master (like a PC)

I suggest that you need to learn more about USB a UART before trying to work them together - try Wikipedia

All the best

Bobi

The microcontroller specialist

 

[motofreek]

Thanks guys for your responses. After doing some reading I realised that the phone I intend to use DOES support a serial conection but I'm not exactly sure how to connect it.

It's a Moto V400 and here are the pinouts..

Mobile phone
interface pin Description

1 GND
2 R=25 or 33 KOhm to GND in data or charge cable
3 +6v charge voltage
4 Tx
5 Rx
6 RTS
7 Vbus (connect to pin 3 if not used as IC power)
8 CTS
9 DCD
10 RE
11 DTR
12 DSR
13 Serial Enable (if this pin is not pulled to ground your serial cable will not work)

I connected pins 4 and 5 to my PIC's UART and connected all the GND connection but nothing. Do I need to connect the other pins ?

Can anyone assist ?
thanks.

 

[motofreek]

I just finished taking apart the usb cable thinking it would have at least 13 wires for me to play around with but it only has 4 for USB !

I'll have to go directly on the pins but I need some help please as to which pins to use !

 

[vysakhpillai]

for uart connection try this

 

[Suresh.sumo]

Hi everyone. I'm doing project in t same field of pic interfacing gsm. We hav done all t initial steps. We struck in communicating pic to gsm. We used nokia 3310 for gsm modem. We cannot get t "ok" msg in hyperterminal using AT command.

 

[Defennder]

Hi everyone. I'm doing project in t same field of pic interfacing gsm. We hav done all t initial steps. We struck in communicating pic to gsm. We used nokia 3310 for gsm modem. We cannot get t "ok" msg in hyperterminal using AT command.

Hi Suresh,

From what I've read, it looks like the Nokia 3310 doesn't support AT commands.
See here for eg.