Gm47

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Gm47

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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by ken on Wed May 30 13:59:46 MST 2012
hi, i am currently working on this schematic, http://www.serasidis.gr/circuits/SMSremoteV3/images/schematicLarge.GIF, but connected to lpc1769, can i have some advice if the circuit is correct and the TD and RD to be connected to LPC1769 uart3 TD and RD respectively, your help is much appreciated.:)
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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by fastfastmcu on Fri Jun 08 16:44:44 MST 2012
That makes no sense, a signal needs a reference and UART is not a differential standard.  Both devices must be powered by the same power supply/computer.  Read up on proper Grounding Practices.

Check your connections again.  Your GND-GND might be shorting a signal it shouldn't.  Also, check the voltages on your LPC and GM47 positive supply rails.  If you are powering both off the same power supply but with long wires then each will have a different 'ground'.
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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by ken on Fri Jun 08 12:03:11 MST 2012
Hi, i have been able to communicate with the gm47 by means of hyper-terminal.And the lpc1769 is working. But i have this problem that once i interface the gm47 and lpc1769 gnd to gnd the gsm module doesn't seems to be working.

thanks for replying.
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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by fastfastmcu on Fri Jun 08 05:26:18 MST 2012
GSM modules generally require CTS and RTS to function correctly.

If you are having this many problems, are you sure both devices work?  Have you been able to communicate with the GM47 by any other means?  Have you used your LPC1769 to communicate with any other UART device?

Look into buying a cheap PL2303 USB-UART module (or a FT232R module as suggested earlier).  The ones with 6 pins have VCC-TXD-RXD-DTR-RTS-GND.

Try the [FONT=Arial]/Examples/USBDEV/USB_VirtualCom/[/FONT] demo from the LPC17xx PDL with is working USB-UART code.
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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by ken on Sun Jun 03 00:29:03 MST 2012
hi, even if my data flow control by default is hardware flow control, can i communicate with the module when my CTS and RTS is short together. sorry for posting so much questions, as i'm new to this communication.
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lpcware
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NXP Employee
Content originally posted in LPCWare by ken on Sat Jun 02 23:56:39 MST 2012
hi, my pin 34 does produce a voltage of 2.7 even if i have ground. it.
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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by martinho on Sat Jun 02 23:41:50 MST 2012
Did You read the HW manual of the GM47? Pin 14 needs to be driven low to startup an the released! If You connect it directly to ground Your GM47 will never start. You can use pin 34 (VIO) to check if the Module is ON or OFF.
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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by ken on Sat Jun 02 22:58:24 MST 2012
hi, these are the codes which i used to test with the gm47.

void init_uart(void)
{
  UART_CFG_Type uartCfg;
  uartCfg.Baud_rate = 5400;
  uartCfg.Databits = UART_DATABIT_8;
  uartCfg.Parity = UART_PARITY_NONE;
  uartCfg.Stopbits = UART_STOPBIT_1;
  //pin select for uart3
  pinsel_uart3();
  //supply power & setup working par.s for uart3
  UART_Init(LPC_UART3, &uartCfg);
  LPC_UART3-> FCR = (UART_FCR_FIFO_EN | UART_FCR_RX_RS|UART_FCR_TX_RS);
  //enable transmit for uart2
  UART_TxCmd(LPC_UART3,ENABLE);

//Initialize FIFO register
  UART_FIFO_CFG_Type FIFOCfg;
      FIFOCfg.FIFO_DMAMode = DISABLE;
      FIFOCfg.FIFO_Level = UART_FIFO_TRGLEV2;
      FIFOCfg.FIFO_ResetRxBuf = ENABLE;
      FIFOCfg.FIFO_ResetTxBuf = ENABLE;
      UART_FIFOConfig(LPC_UART3, &FIFOCfg);
}
int main(){
init_uart();

while (1)
{


//test sending message
strcpy(msg, "AT+CMGF=1\r");

UART_Send(LPC_UART3, (uint8_t *)msg , strlen(msg), BLOCKING);


Timer0_Wait(500);
len = 0;

do
{

UART_Receive(LPC_UART3, &data, 1, BLOCKING);

if (data != '\r')
{
len++;
line[len-1] = data;

}

} while ((len<64) && (data != '\r'));
printf ("%s\n",line);

line[len]=0;
return 0;
}
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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by ken on Sat Jun 02 22:27:27 MST 2012
Hi, my lpc1769 is able to communicate with other lpc1769 however whenever i establish connection with the module, it does not respond or it replies with a string of digits.

The output voltage of the LPC1769 is 3.1v does it affects the communication between gm47 and the LPC1769? or should i used UART 2 of the gm47 to test the communication?
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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by fastfastmcu on Sat Jun 02 21:59:51 MST 2012
You should be able to leave pin 14 unconnected or add a pull-up resistor of 47k to 3.3V.

If you have not established communication with the module and enabled it then it won't do anything.  The antenna should be off.

You don't need a USB-UART module to test the GM47 but you need some way to test if it works at all.  Is your LPC1769's UART able to communicate with other devices?
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lpcware
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NXP Employee

Content originally posted in LPCWare by ken on Sat Jun 02 05:37:34 MST 2012
[ATTACH]780[/ATTACH], this is the schematic which i used to connect to the lpc 1769 Tx and Rx, is there any way i can do to interface without using  MM232R or USB-UART?
your help is appreciated.

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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by ken on Fri Jun 01 22:28:26 MST 2012
hi, can i check that if i short pin 14 to ground permanently does it affect the operation of the gsm module? or should i have implemented a latching circuit for the pin 14, if so do you have any alternative to approach this problem? I have met with the problem that the pin 38 of the module output a 2.3v which supposed to be a 2.7v, does it mean that my antenna is not receiving enough signal strength.:confused:
your help is appreciated, thank you very much.:)
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lpcware
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Content originally posted in LPCWare by fastfastmcu on Thu May 31 22:26:51 MST 2012
You do not need a MAX232 since the GSM module operates at ~3V, not +/-5V.  Interface using the circuit in "3.7 Interfacing to a 3.3V uProcessor".

If you look at the pinout on Pg30, [B]TD[/B] is "Transmitted Data from DTE" so it should connect to your LPC1769's [B]TX[/B] pin.  [B]RD[/B] to [B]RX[/B], [B]GND[/B]-[B]GND[/B].

Pin 14 is open drain ON/OFF.  After applying power, short momentarily to GND to reset the GSM module.

GSM modules consume a lot of power so add extra decoupling caps close to the power supply.

Try communicating with the GSM module using a MM232R or similar USB-UART device to rule out problems with the GSM module.
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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by ken on Thu May 31 19:57:05 MST 2012
Hi, i've tried with the above connection to UART3, but no responds. 48_Design_Guidelines_R1B.pdf"]http://archive.sierrawireless.com/resources/AirPrime/GM47-48/GM47-48_Design_Guidelines_R1B.pdf[/URL], this document shows that the PIN TD is an INPUT and RD is an output, should i continue with the connection which u have suggested. Should the connection be connected to UART 1 or do i need to have an addition circuit to max232? really appreciated your help. thanks in advance.
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lpcware
NXP Employee
NXP Employee
Content originally posted in LPCWare by NXP_Europe on Thu May 31 15:00:14 MST 2012
Hi Ken,

connect TD -> RxD (lpc1769)
connect RD <- TxD (lpc1769)
connect gnd <-> gnd

see for connection of the LPCXexpresso:
http://ics.nxp.com/support/documents/microcontrollers/pdf/lpcxpresso.lpc1769.schematic.pdf

Use an UART example code.
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