Hi everyone ,
i'm using PCF8574P to interface 7 segment display with MSP430F2274 micro controller. i am also using a example program "msp430x22x4_uscib0_i2c_02 " from " slac123d " this zib file. according to the diagram in the program i have connected the hardware. i added the program for your reference .
Hardware details:
Pullup resistors = 10k(for scl),10k(for sda) , connected with VCC of 2274 (refered diagram in the program)
PCF8574p slave address : 0x20 ->>> A0=A1=A2=VSS, grounded
P0 pin of PCF8574 is connected to ground, [VSS]
p1,p2,p3 pins of PCF8574 is connected to supply [VCC]
p4-p7 pins of PCF8574 is connected to 4 pins of 7 segment display , the common pin of 7 segment display is connected to supply
according to the program [ 7 segment is common anode type so , i connected to supply ] if PCF8574 IC gets zero voltage in P0/p1/p2/P3 then one of this segment in P4/P5/P6/P7 segment must glow.
but if I run the program the I/O pins PCF8574 P0-P7 is getting voltage 3.35V [ VCC]
so, no 7segment is glowing??????????
can somebody provide me the reason for the problem or the proper Master( Transmit mode ) code with PCF interface .....
//******************************************************************************
// MSP430F22x4 Demo - USCI_B0 I2C Master Interface to PCF8574, Read/Write
//
// Description: I2C communication with a PCF8574 in read and write mode is
// demonstrated. PCF8574 port P is configured with P0-P3 input, P4-P7. Read
// P0-P3 input data is written back to Port P4-P7. This example uses the
// RX ISR and generates an I2C restart condition while switching from
// master receiver to master transmitter.
// ACLK = n/a, MCLK = SMCLK = TACLK = BRCLK = default DCO = ~1.2MHz
//
// MSP430F22x4
// -----------------
// /|\ /|\ /|\| XIN|-
// 10k 10k | | |
// PCF8574 | | --|RST XOUT|-
// --------- | | | |
// --->|P0 SDA|<-|---+---->|P3.1/UCB0SDA |
// --->|P1 | | | |
// --->|P2 | | | |
// --->|P3 SCL|<-+---------|P3.2/UCB0SCL |
// <---|P4 | | |
// <---|P5 | | |
// <---|P6 | | |
// <---|P7 | | |
// +--|A0,A1,A2 | | |
// | | | | |
// \|/
//
// Andreas Dannenberg
// Texas Instruments Inc.
// March 2006
// Built with CCE Version: 3.2.0 and IAR Embedded Workbench Version: 3.41A
//******************************************************************************
#include "msp430x22x4.h"
void main(void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop Watchdog Timer
P3SEL |= 0x06; // Assign I2C pins to USCI_B0
UCB0CTL1 |= UCSWRST; // Enable SW reset
UCB0CTL0 = UCMST+UCMODE_3+UCSYNC; // I2C Master, synchronous mode
UCB0CTL1 = UCSSEL_2+UCSWRST; // Use SMCLK, keep SW reset
UCB0BR0 = 12; // fSCL = SMCLK/12 = ~100kHz
UCB0BR1 = 0;
UCB0I2CSA = 0x20; // Set slave address
UCB0CTL1 &= ~UCSWRST; // Clear SW reset, resume operation
IE2 |= UCB0RXIE; // Enable RX interrupt
TACCTL0 = CCIE; // TACCR0 interrupt enabled
TACTL = TASSEL_2 + MC_2; // SMCLK, contmode
while (1)
{
__bis_SR_register(CPUOFF + GIE); // CPU off, interrupts enabled
UCB0CTL1 &= ~UCTR; // I2C RX
UCB0CTL1 |= UCTXSTT; // I2C start condition
while (UCB0CTL1 & UCTXSTT); // Loop until I2C STT is sent
UCB0CTL1 |= UCTR + UCTXSTT; // I2C TX, start condition
__bis_SR_register(CPUOFF + GIE); // CPU off, interrupts enabled
while (UCB0CTL1 & UCTXSTT); // Loop until I2C STT is sent
UCB0CTL1 |= UCTXSTP; // I2C stop condition after 1st TX
}
}
#pragma vector = TIMERA0_VECTOR
__interrupt void TA0_ISR(void)
{
__bic_SR_register_on_exit(CPUOFF); // Exit LPM0
}
// USCI_B0 Data ISR
#pragma vector = USCIAB0TX_VECTOR
__interrupt void USCIAB0TX_ISR(void)
{
UCB0TXBUF = (UCB0RXBUF << 4) | 0x0f; // Move RX data to TX
__bic_SR_register_on_exit(CPUOFF); // Exit LPM0
}
any help could be welcomed on this issue.....
