atmel:smsrx [DBZoo]

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======Introduction ======

**Never did get a picture of this project running**

The idea is that an SMS phone can be used to receive SMS messages that can then be displayed on a large format message board.

=====What is needed=====

^ Hardware ^ Description ^
| {{devbrd.gif}} | **Atmel AVR Microcontroller Development System**\\  This kit was kindly provided to me by the friendly people over at http://www.btinternet.com/~e2one/avrbrd/ |
| {{lcd8x24.gif}} | **8x24 LCD Display** \\ Details of how to wire up a 8x24 display to the development board can be found at http://www.btinternet.com/~e2one/avrbrd/ (see the 8x24 LCD Project). If you use a smaller display then you will have to modifying the code to suit. |
| {{7110_main.gif}} | **A mobile phone** \\ I used a NOKIA 7110 but any phone that has a built in modem should be ok. |
| {{dlr3.gif}} | **A DLR-3 cable**\\ A phone connector wired to a DB9-F.\\ If you don't have one or you can't afford to buy it then there are some good solutions for making your own |

====The Software====
  * As the ATMEL AT90S2313 only has 2k of code space the demo version of [[http://www.mcselec.com/bascom-avr.htm|BASCOM]] can be used without hitting any of its restrictions. 
  * Hyperterminal or any suitable terminal emulation package. Useful for making sure that your GPS unit is tranmitting data. 


=====RS232 madness=====
A great site for the wiring of all things RS232 can found at http://www.lammertbies.nl/comm/cable/RS-232.html
{{ 9d.gif }}


**9 Pin Connector on a DTE device (Phone connection)**

^ Pin Number ^ Direction of signal: ^
|1 |Carrier Detect (CD) (from DCE) Incoming signal from a modem |
|2 |Received Data (RD) Incoming Data from a DCE |
|3 |Transmitted Data (TD) Outgoing Data to a DCE |
|4 |Data Terminal Ready (DTR) Outgoing handshaking signal |
|5 |Signal Ground Common reference voltage |
|6 |Data Set Ready (DSR) Incoming handshaking signal |
|7 |Request To Send (RTS) Outgoing flow control signal |
|8 |Clear To Send (CTS) Incoming flow control signal |
|9 |Ring Indicator (RI) (from DCE) Incoming signal from a modem |




====Phone Connector====
{{ pins7110.gif }}

**Nokia 7110 DLR-3**
^ Pin ^ Signal ^ Specs ^
|1 |V In | 0..8.5V, 0..850mA |
|2 |Chrg Control | PWM, 32..37 Hz, 1..99% |
|3 |XMic / Device Selector | |
|4 |SGnd / DLR-3 VCC | 3.3 V  |
|5 |XEar / DLR-3 RTS | |
|6 |MBus | 9600bps |
|7 |FBus Rx / Modem | 9600 - 230.400 bps\\ < 0.8V : '0'\\ > 2.0V : '1'  |
|8 |FBus Tx / Modem | 9600 - 230.400 bps\\ < 0.8V : '0' @ max. 4mA > 1.7V : '1' @ max. 4mA  |
|9 |LGnd | |

====Inside the AVR cable====
The standard cable that is supplied with the AVR development kit uses a 3 pin configuration for RS232 data. It is wired as a DTE with built in loop back handshaking.

{{ avr232db9.gif }}
**AVR RS232 DB9 wiring**
The DLR-3 cable expects partial handshaking from a DCE. The problem is the AVR board does not implement any hardware handshaking and is wired as a DTE.


====AVR/DLR-3 cable====
To overcome this problem we will build a new cable. This will be wired so that the AVR board is seen as DCE, additionally it will also have a hardwired active DTR signal.

{{ db9_avr.png }}

^AVR board IDC ^Connector ^ Function ^
|1 |5 |Signal ground |
|2 |3 |Tx -> Rx |
|3 |2 |Rx -> Tx |
|4 |4 |Vcc -> DTR |

{{ db9_avr_photo.jpg }}

The purpose of this null modem cable is to make the phone think there is a DCE device listening
{{tag>avr}}