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Hello, I am trying to write a Set of Bit Bang I2C Functions to communicate with a SRF08 Range Finder. I found some code by Grant Beattie for the HC11 and have addapted it for the 89LPC932. Now I have the Start, stop, and Write Byte functions working, but the Read function is not working. I have the suggested pull-up resistors and when I run the code the value outputs 255 meaning the data line never falls. This is my code please help.
unsigned char I2cRead(unsigned char count) { unsigned char mask; unsigned char value; unsigned char index = 0; while(count) { mask = 0x80; value = 0x00; while(mask) // Do the 8 data bits... { SclHi(); // Set SCL //and wait for it to go hi. I2cDelay(); if( GetSda() ) // Read the bit value |= mask; // the returned byte. SclLo(); // Bring SCL low again I2cDelay(); mask >>= 1; } Readvalue = value; // Save the read byte. index++; count--; if(count) // If not the last byte, ACK { SdaLo(); // Bring SDA low for ACK. SclHi(); // Clock high. I2cDelay(); SclLo(); // Clock low. SdaHi(); // Release SDA. I2cDelay(); } } SdaHi(); // SDA high for NACK on last byte. SclHi(); // Clock high. I2cDelay(); SclLo(); // Clock low. I2cDelay(); return 0; }
in my i2c_init There is an IICinit in the codearchitect, make sure nothing (eg pin configurations) is lost from there. Also, do you have pullup resisttors on the two lines? Erik
Pin Configs are OK and I have 1.5k pull ups.
Hey Erik, Looks Like it was a bad Emulator the SCL pin was always high. Put in a New Emulator and it is starting to work. I think It is good now. Thank You for all of your help. Kenny
One more question if you are still there Erik. I have the code architect functions working in that they go to all of the correct interrupts, but I do not receive any data back from case 58: my I2Dat value is always zero. Just wondering if you have seen this before. This is my Init routine.
void i2c_init( unsigned char address, // The 7-bit I2C address to use bit generalcall // 1 = respond to general call, 0 = ignore // general call ) { // set pins to open-drain P1M1 |= 0x0C; P1M2 |= 0x0C; // configure I2C address I2ADR = 0x00; //I2ADR = address << 1; //if (generalcall) //{ // I2ADR |= 0x01; //} // if // configure internal SCL generator //Page 79 of the user manual gives these values for close to 400Kbit/S //SCLH (SCL Duty Cycle Register High Byte) I2SCLH =0x08; //SCLL (SCL Duty Cycle Reister Low Byte) I2SCLL =0x07; // configure I2C interface // use internal SCL generator I2CON = 0x44; // set interrupt priority to 0 IP1 &= ~0x01; IP1H &= ~0x01; // initial status mi2cstatus = I2C_IDLE; // enable interrupt EI2C = 1; EA=1; } // i2c_init
but I do not receive any data back from case 58:
// no ACK for data byte case 0x58