GSM modem interfacing with MSP430F2013

The msp430f2013 does not have UART ports. So I found that a software UART
can be created and I followed the code from J H Davies book. As I have
mentioned in the question, i am basically trying to interface a GSM modem
to the MSP. My question are'

1. Is it possible to do this on a software UART?

2. Once I have compiled the software UART program, how do I check it? Can
I do this on Hyperterminal or putty?

I have read the various discussions on this forum about software UART but
my doubt is not cleared.

The code i used for software UART is below.

#include <io430x20x3.h> // Header file for this device
#include <stdint.h> // Integers of defined sizes
#include "uartlib.h" // Library for software UART
#define LED P1OUT_bit.P1OUT_0   // Output pin for LED (active high)
uint8_t RXBUF; // Buffer for received byte
uint8_t TXBUF; // Buffer for byte to transmit#define BITTIME ((1000000 +
4800)/9600) // Cycles of TACLK per bit , 1MHz
#define HALFTIME (BITTIME/2) // Cycles for half a bit
void UARTSetUp ( void )
{
TACTL = TASSEL_2 | MC_2; // TACLK = SMCLK = 1MHz
TACCTL0 = OUT | OUTMOD_0 | CCIFG;
TACCTL1 = CM_2 | CCIS_1 | SCS | CAP | OUTMOD_0 | CCIE;
RXIFG = 0; // Buffer empty , no byte received
TXIFG = 1; // Buffer empty , ready to accept TX
}
//----------------------------------------------------------------------
// Write byte to TXBUF; clears flag , starts transmitter if necessary
//----------------------------------------------------------------------
void WriteTXBUF ( const uint8_t TXData)
{
TXBUF = TXData; // Transfer data to buffer
TXIFG = 0; // Clear interrupt flag
TACCTL0_bit. CCIE = 1; // Enable interrupts if inactive ,
} // no effect if already running
//----------------------------------------------------------------------
// Read byte from RXBUF; clears flag
//----------------------------------------------------------------------
uint8_t ReadRXBUF ( void )
{
RXIFG = 0; // Clear interrupt flag
return RXBUF; // Read data from buffer
}
//----------------------------------------------------------------------
// ISR for Timer_A2 , channel 0: transmission
//----------------------------------------------------------------------
#pragma vector = TIMERA0_VECTOR
_ _interrupt void TIMERA0_ISR ( void ) // Acknowledged automatically
{
static uint8_t TXBitCount = 0; // Count bits transmitted
static uint16_t TXShiftReg; // Shift register for transmission
LED = 1; // Show start of activity
if (TXBitCount == 0) 
{ // Ready to start new byte
if (TXIFG == 0) 
{ // Byte available to transmit
TXShiftReg = TXBUF; // Load data from buffer
TXShiftReg |= BIT8; // Add stop bit after msb
TXIFG = 1; // Show that buffer is available
TXBitCount = 9; // Number of bits including stop bit
TACCR0 = TAR + BITTIME; // Delay until start of start bit
TACCTL0 = OUTMOD_5 | CCIE; // Clr output on compare for ST
} 
else 
{ // No data available , shut down
TACCTL0 = OUT | OUTMOD_0 | CCIFG; // Idle: output high ,
} // disable interrupt , set flag for int 'pt when reenabled
} 
else
{ // Send next bit
if (TXShiftReg & BIT0) 
{ // Send 1 next
TACCTL0 = OUTMOD_1 | CCIE; // Set output on compare
} 
else 
{ // Send 0 next
TACCTL0 = OUTMOD_5 | CCIE; // Clear output on compare
}
TACCR0 += BITTIME; // Delay until next bit
TXShiftReg >>= 1; // Shift right , remove lsb
--TXBitCount; // Update bit counter
}
LED = 0; // Show end of activity
}
//----------------------------------------------------------------------
// ISR for Timer_A2 , channel 1 and timer core ( inactive): reception
//----------------------------------------------------------------------
#pragma vector = TIMERA1_VECTOR
_ _interrupt void TIMERA1_ISR ( void ) // NOT acknowledged automatically
{
static uint8_t RXBitCount = 0; // Count bits received
static uint8_t RXShiftReg; // Shift register for reception
LED = 1; // Show start of activity
TACCTL1_bit. CCIFG = 0; // Acknowledge interrupt , clear flag
if (TACCTL1_bit.CAP) 
{ // Capture mode , start bit detected
TACCTL1_bit.CAP = 0; // Switch to sampling (compare ) mode
TACCR1 += HALFTIME; // Wait for half a bit time
RXBitCount = 9; // Bits to receive including ST, SP
} 
else 
{
switch (RXBitCount) 
{
case 9: // Start bit
if (TACCTL1_bit. SCCI) 
{ // Error: start bit should be low
TACCTL1_bit.CAP = 1; // Abandon reception
} 
else 
{ // Correct: proceed to receive data
TACCR1 += BITTIME; // Wait for complete bit time
--RXBitCount; // Update bit counter
}
break ;
case 0: // Stop bit
if (TACCTL1_bit. SCCI) 
{ // Correct: stop bit should be high
RXBUF = RXShiftReg; // Store data into buffer
RXIFG = 1; // Raise flag to show new data
} // (discard byte if stop bit low)
TACCTL1_bit.CAP = 1; // Return to capture mode
break ;
default : // Data bit (lsb first), cases 1-8
RXShiftReg >>= 1; // Shift data , clear msb for new bit
if (TACCTL1_bit. SCCI) 
{
RXShiftReg |= BIT7; // Set received bit if high
}
TACCR1 += BITTIME; // Wait for complete bit time
--RXBitCount; // Update bit counter
break ;
}
}
LED = 0; // Show end of activity
}


---------------------------------------
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On 16/04/15 02:53, Nivi21 wrote:
> The msp430f2013 does not have UART ports. So I found that a software UART
> can be created and I followed the code from J H Davies book. As I have
> mentioned in the question, i am basically trying to interface a GSM modem
> to the MSP. My question are'
> 
> 1. Is it possible to do this on a software UART?

A software UART can do anything that a hardware UART can do - but it
will use a lot more cpu time, especially for faster baud rates.

However, your best approach would be to change microcontroller.  There
are lots of msp430 devices with proper UARTs, as well as many
alternative microcontrollers with more processing power and more memory
(which you might need in order to do something useful with the GSM
modem) - since you currently have an msp430, you might want to look at
the new TI msp432 family.  (I haven't used them myself.)

> 
> 2. Once I have compiled the software UART program, how do I check it? Can
> I do this on Hyperterminal or putty?

Don't try Hyperterminal - it can cause more problems than it solves.
But Putty is a perfectly good way to check that your software UART is
working as expected.

> 
> I have read the various discussions on this forum about software UART but
> my doubt is not cleared.
> 
> The code i used for software UART is below.
> 

<snipped the code - I haven't read it>