add GetChecksum function

[fffonceca]

So a friend of mine had a hard time fighting with the checksum. It would be nice to have a function that calculates that for you. In the master branch i added this function as GetChecksum. It receives an array containing the information of registers and the length of the array (amount of registers to write into). Then it returns the checksum:

unsigned short ATM90E26_UART::GetChecksum(unsigned short *hex_values, int length) {
    unsigned short value = 0x0000;
    unsigned char lsb, msb;
    int chk1 = 0, chk2 = 0;

    for (int i = 0; i < length; i++) {
        msb = (hex_values[i] >> 8);
        lsb = (hex_values[i] & 0x00FF);
        chk1 += msb + lsb;
        chk2 ^= msb ^ lsb;
    }
    value = chk1 % 0x100;
    value += (chk2 << 8);  

    return value;
}

This function gets the defined checksum from datasheet. For testing you can do literally gcc main.c copying the following code:

#include <stdio.h>

#define CfgRegLen1 11  // Amount of register for Checksum 1
#define CfgRegLen2 10  // Amount of register for Checksum 2
#define PLconstH 0x21  // High Word of PL_Constant
#define PLconstL 0x22  // Low Word of PL_Constant
#define Lgain 0x23     // L Line Calibration Gain
#define Lphi 0x24      // L Line Calibration Angle
#define Ngain 0x25     // N Line Calibration Gain
#define Nphi 0x26      // N Line Calibration Angle
#define PStartTh 0x27  // Active Startup Power Threshold
#define PNolTh 0x28    // Active No-Load Power Threshold
#define QStartTh 0x29  // Reactive Startup Power Threshold
#define QNolTh 0x2A    // Reactive No-Load Power Threshold
#define MMode 0x2B     // Metering Mode Configuration
#define Ugain 0x31     // Voltage rms Gain
#define IgainL 0x32    // L Line Current rms Gain
#define IgainN 0x33    // N Line Current rms Gain
#define Uoffset 0x34   // Voltage Offset
#define IoffsetL 0x35  // L Line Current Offset
#define IoffsetN 0x36  // N Line Current Offse
#define PoffsetL 0x37  // L Line Active Power Offset
#define QoffsetL 0x38  // L Line Reactive Power Offset
#define PoffsetN 0x39  // N Line Active Power Offset
#define QoffsetN 0x3A  // N Line Reactive Power Offset

unsigned short GetChecksum(unsigned short *hex_values, unsigned short length) {
    unsigned short value = 0x0000;
    unsigned char lsb, msb;
    int chk1 = 0, chk2 = 0;

    for (int i = 0; i < length; i++) {
        msb = (hex_values[i] >> 8);
        lsb = (hex_values[i] & 0x00FF);
        chk1 += msb + lsb;
        chk2 ^= msb ^ lsb;
    }
    value = chk1 % 0x100;
    value += (chk2 << 8);  

    return value;
}

int main()
{
    unsigned char reg_adr1[CfgRegLen1] = {PLconstH,PLconstL,Lgain,Lphi,Ngain,Nphi,PStartTh,PNolTh,QStartTh,QNolTh,MMode};
    unsigned short reg_values1[CfgRegLen1] = {0x00B9,0xC1F3,0x1D39,0x0000,0x0000,0x0000,0x08BD,0x0000,0x0AEC,0x0000,0x9422};

    unsigned char reg_adr2[CfgRegLen2] = {Ugain,IgainL,IgainN,Uoffset,IoffsetL,IoffsetN,PoffsetL,QoffsetL,PoffsetN,QoffsetN};
    unsigned short reg_values2[CfgRegLen2] = {0xD464,0x6E49,0x7530,0x0000,0x0000,0x0000,0x0000,0x0000,0x0000,0x0000};

    printf("Checksum1: %04X\n", GetChecksum(reg_values1, CfgRegLen1));
    printf("Checksum2: %04X\n", GetChecksum(reg_values2, CfgRegLen2));

    return 0;
}

Maybe more assist is needed so InitEnergyIC() function can receive properly a init_config_t struct with initial configuration...

Regards!

[fffonceca]

I did change init function so GetChecksum can be called inside. This way we can use this function to recalculate Checksum if user change some configuration.

[fffonceca]

Now i finally ended data types, i was not aware of unsigned char = uint8_t and unsigned short = uint16_t