Other Parts Discussed in Thread: PCA9557
I am new to both TI devices(I am using MSP430F6779A) and I2C. I learned the basic but now I am facing a problem. I am unable to read input which is connected to an I/O expander (slave) and then to the I2C pins (SDA and SCL) of the microcontroller IC. There are in total 8 input pins connected to the I/O expander whose state (high or low) can be read by the I2C bus. My question is that how do I choose the I/O expander pin whose input I want to read. Suppose, I have 8 input pins at I/O expander from DI1 to DI8. Now, I want to read the input only at DI1. I have assigned correct slave address by reading the datasheet of my IO expander (PCA9557). Datasheet link - http://www.ti.com/lit/ds/symlink/pca9557.pdf. But, how do I choose the pin whose input I want to read ( for eg. DI1). I have made changes to the existing example code given by texas instruments.
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#include "driverlib.h"
//*****************************************************************************
//! This example shows how to configure the I2C module as a master for
//! single byte reception in interrupt driven mode. The address of the slave
//! module that the master is communicating with also set in this example.
//!
//! Description: This demo connects two MSP430's via the I2C bus. The master
//! reads from the slave. This is the MASTER CODE. The data from the slave
//! transmitter begins at 0 and increments with each transfer.
//! The USCI_B0 RX interrupt is used to know when new data has been received.
//! ACLK = n/a, MCLK = SMCLK = BRCLK = DCO = 1MHz
//!
//! /|\ /|\
// //! MSP430F67791A 10k 10k MSP430F67791A
//! slave | | master
//! ----------------- | | -----------------
//! -|XIN P2.6/UCB0SDA|<-|----+->|P2.6/UCB0SDA XIN|-
//! | | | | | 32kHz
//! -|XOUT | | | XOUT|-
//! | P2.5/UCB0SCL|<-+------>|P2.5/UCB0SCL |
//! | | | P1.0|--> LED
//!
//! This example uses the following peripherals and I/O signals. You must
//! review these and change as needed for your own board:
//! - I2C peripheral
//! - GPIO Port peripheral (for I2C pins)
//! - SCL2
//! - SDA
//!
//! This example uses the following interrupt handlers. To use this example
//! in your own application you must add these interrupt handlers to your
//! vector table.
//! - USCI_B0_VECTOR.
//!
//
//*****************************************************************************
//*****************************************************************************
//
//Set the address for slave module. This is a 7-bit address sent in the
//following format:
//[A6:A5:A4:A3:A2:A1:A0:RS]
//
//A zero in the "RS" position of the first byte means that the master
//transmits (sends) data to the selected slave, and a one in this position
//means that the master receives data from the slave.
//
//*****************************************************************************
#define SLAVE_ADDRESS 0x33
uint8_t RXData;
void main(void)
{
//Stop WDT
WDT_A_hold(WDT_A_BASE);
//Set the XT1 frequency to UCS
UCS_setExternalClockSource(32768, 0);
//Configure Pins for I2C (UCB0SCL, UCB0SDA)
//Set P2.5 and P2.6 as Module Function Input
GPIO_setAsPeripheralModuleFunctionInputPin(
GPIO_PORT_P4,
GPIO_PIN4 + GPIO_PIN5
);
GPIO_setAsOutputPin( GPIO_PORT_P5,
GPIO_PIN0 + GPIO_PIN7
);
EUSCI_B_I2C_initMasterParam param = {0};
param.selectClockSource = EUSCI_B_I2C_CLOCKSOURCE_SMCLK;
param.i2cClk = UCS_getSMCLK();
param.dataRate = EUSCI_B_I2C_SET_DATA_RATE_400KBPS;
param.byteCounterThreshold = 1;
param.autoSTOPGeneration =
EUSCI_B_I2C_SEND_STOP_AUTOMATICALLY_ON_BYTECOUNT_THRESHOLD;
EUSCI_B_I2C_initMaster(EUSCI_B0_BASE, ¶m);
//Specify slave address
EUSCI_B_I2C_setSlaveAddress(EUSCI_B0_BASE,
SLAVE_ADDRESS
);
//Set Master in receive mode
EUSCI_B_I2C_setMode(EUSCI_B0_BASE,
EUSCI_B_I2C_RECEIVE_MODE
);
//Enable I2C Module to start operations
EUSCI_B_I2C_enable(EUSCI_B0_BASE);
EUSCI_B_I2C_clearInterrupt(EUSCI_B0_BASE,
EUSCI_B_I2C_RECEIVE_INTERRUPT0 +
EUSCI_B_I2C_BYTE_COUNTER_INTERRUPT
);
GPIO_setOutputLowOnPin( GPIO_PORT_P5,
GPIO_PIN7 );
GPIO_setOutputHighOnPin( GPIO_PORT_P5,
GPIO_PIN7 );
GPIO_setOutputLowOnPin( GPIO_PORT_P5,
GPIO_PIN0 );
__delay_cycles(1000000);
while(1)
{
__delay_cycles(2000);
// I2C start condition
RXData = EUSCI_B_I2C_masterReceiveSingleByte(EUSCI_B0_BASE); // When I run the code, it get stuck here.
GPIO_setOutputLowOnPin( GPIO_PORT_P5,
GPIO_PIN7 );
if( RXData)
{
GPIO_setOutputHighOnPin( GPIO_PORT_P5,
GPIO_PIN0 + GPIO_PIN7
);
__delay_cycles(1000000);
}
else
{
GPIO_setOutputHighOnPin( GPIO_PORT_P5,
GPIO_PIN7 );
GPIO_setOutputHighOnPin( GPIO_PORT_P5,
GPIO_PIN0 );
__delay_cycles(1000000);
}
}
}
The function code where I am stuck is here.
uint8_t EUSCI_B_I2C_masterReceiveSingleByte(uint16_t baseAddress)
{
//Set USCI in Receive mode
HWREG16(baseAddress + OFS_UCBxCTLW0) &= ~UCTR;
//Send start
HWREG16(baseAddress + OFS_UCBxCTLW0) |= (UCTXSTT + UCTXSTP);
//Poll for receive interrupt flag.
while(!(HWREG16(baseAddress + OFS_UCBxIFG) & UCRXIFG))
{
;
}
//Send single byte data.
return (HWREG16(baseAddress + OFS_UCBxRXBUF));
}
Please help me with this. Also, i want to ask is there any monitor where i could see the inputs at the microcontroller IC? Like the serial monitor at Arduino. I am using JTAG as programmer/debuggr and IAR as IDE. Thanks in advance.
