How do I sum the values of a buffer

General
1

I need to calculate the sum of the HEX values of a buffer for my serialport string checksum value.
for example, here is the buffer:
msg.payload = Buffer.from([0xca,0x07,0x06,0x01,0x17,0x01,0x00,0x00,0x00,0x00,0x26,0x35]);
To get the checksum I need to sum index 1 through 9.
The sum of 0x07,0x06,0x01,0x17,0x01,0x00,0x00,0x00,0x00 = 0x26 = checksum
Index 10 is the checksum in the buffer

I would also like to know what the best way would be to create the buffer once I have calculated the checksum.
My guess is I would use "concat". If you have any examples, you can share that would be great.

A variable value is being sent in the serialport message, so the checksum will change everytime the variable value changes.

2

I am not super familiar with buffer array's but apperently you can treat them like normal arrays.
According to AI:

// input would be msg.payload
const input = [0xca, 0x07, 0x06, 0x01, 0x17, 0x01, 0x00, 0x00, 0x00, 0x00, 0x26, 0x35] 
const buffer = Buffer.from(input)

// Calculate the checksum by summing up values from index 1 to 9
let checksum = 0;
for (let i = 1; i <= 9; i++) {
    checksum += buffer[i];
}

// Convert the calculated checksum to a hexadecimal string and ensure it matches the expected value at index 10
const expectedChecksum = buffer[10].toString(16).toUpperCase();
const actualChecksum = (checksum & 0xFF).toString(16).toUpperCase(); // Ensure we only consider the last byte of the sum

node.warn(`Expected Checksum: ${expectedChecksum}`);
node.warn(`Actual Checksum:   ${actualChecksum}`);

// Verify if they match
if (expectedChecksum === actualChecksum) {
    node.warn("The checksum is correct.");
} else {
    node.warn("There is an error in the checksum calculation.");
}
3

Thanks - this was very helpful.

4

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