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Electronics => Microcontrollers => Topic started by: JonPyro on April 25, 2018, 01:49:23 pm

Title: 16f1825 MCC i2c with PCA985
Post by: JonPyro on April 25, 2018, 01:49:23 pm

Hi All,

I am a little lost as I have never really implemented I2C before on a PIC with MCC.

I am trying to talk to the PCA9685 (datasheet : https://www.nxp.com/docs/en/data-sheet/PCA9685.pdf (https://www.nxp.com/docs/en/data-sheet/PCA9685.pdf)) on a servo driver board bought off ebay using a 16f1825 and using MCC to generate the I2C functions. However, I am at a loss to work out how to use the functions MCC has generated.

Here is my thinking, first define the registers from the datasheet I want to access and the new pre-scaler (I want 50hz pwm for servos and not the default 200hz):

Code: [Select]

#define PCA9685_ADDRESS        0x40
#define PCA9685_MODE1          0x00
#define PCA9685_PRESCALE       0xFE
#define PCA9685_MODE1_SLEEP    0x10
#define PCA8695_MODE1_RESTART  0x80

int PreScaleValue = 0x79;

Now in the main program I should be using:

Code: [Select]

void I2C_MasterWrite(
            uint8_t *pdata,
            uint8_t length,
            uint16_t address,
            I2C_MESSAGE_STATUS *pstatus);
So would you write that something along the lines of this if I wanted to sleep the chip and change the pre-scale:

Code: [Select]

    writeBuffer[0] = PCA9685_MODE1_SLEEP;
    writeBuffer[1] = PCA9685_PRESCALE;
    writeBuffer[2] = PreScaleValue;
       
    I2C_MasterWrite(writeBuffer,1, PCA9685_ADDRESS, &status);
Any help would be appreciated ;)