Need some ProntoScript advice with Hex and OR-ing... I need to calculate the checksum of 5 bytes by OR-ing them (I can do the checksum in Excel, but figured it would be better to do in my ProntoScript library).

So, my 5 bytes are assigned as follows:

B1 = "\x17", B2 = "\x2E", B3 = "\x00", B4 = "\x00", B5 = "\x00";

I tried the following:

checkSum = B1 | B2 | B3 | B4 | B5;

However, it does not work properly.

This works:

checkSum = 0x17 | 0x2E | 0x00 | 0x00 | 0x00;

However, I'm storing the bytes in strings (like in B1, B2, ... B5 above).

How do I do the bitwise OR (i.e. | ) on B1, B2, ... B5? I'd like to assign them like I did above (as opposed to B1 = 0x17; B2 = 0x2E, etc.).

Later, when I want to pass bytes 0 to 7 (B0, .... B7) to Serial.match, how
do I concatenate them together to be one "string"? Doing
B0 || B1 || B2 .... || B7 doesn't work.

Advice?

Thanks!

To build an single ascii character with the value you need, you use String.fromCharCode(checksum).

I sure thought there was an example of building up an array of bytes in Barry's documentation along with a checksum.

I'd take a slightly different approach rather than building variables with string values, do everything as integers which makes it easier to calculate checksums and then build a string at the end.

For example, you are treating these as strings up front.

B1 = "\x17", B2 = "\x2E", B3 = "\x00", B4 = "\x00", B5 = "\x00";


I'd build myself an array and stuff in integer values between 0 and 255 (0x00 and 0xFF).

var bytesToSend = [];
var index = 0;
var index2 = 0;

bytesToSend[index++] = 0x17;
bytesToSend[index++] = 0x2E;
bytesToSend[index++] = 0x00;
bytesToSend[index++] = 0x00;
bytesToSend[index++] = 0x00;

var checksum = 0;
var index2 = 0;
for (index2 = 0; index2 < bytesToSend.length; index2++)
checksum |= bytesToSend[index2];

// Append checksum you just calculated onto end of array.
bytesToSend[index++] = checkSum;

// Build a string from the array (not sure if String.fromCharCode(0x00) will
// add a NUL character to a string. Think it does but you will want to confirm.

var stringToSend = '';
for (index2 = 0; index2 < bytesToSend.length; index2++)
stringToSend += String.fromCharCode(bytesToSend[index2]);

Regards,
Lyndel

Ah wonderful. Yeah, now that I've ready your reply, Barry's example makes perfect sense. His example assigned decimals to the variables, while your reply assigns hexadecimals to the variables. I suppose it doesn't matter how the vars are assigned. Thanks so much for your help!

In case anyone with a Sony projector needs to know in the future, here's the results of my testing:

The Sony supports two standby modes. The "Low" mode uses less power (0.5W). However, in "Low" mode, the projector does not respond to Power Status requests. If you send the power status request 2 times in a reow, the first request times out and the second request replies with a NAK error. The "Standard" standby mode uses more power (8W). However, it responds immediately to Power Status requests (it responds saying the projetor is in standby mode). So, if I want to save power, I can just assume that if the response times out, the projector must be in standby mode (in which case I would send a Power On command, and popup the please wait dialog boxes). Or, I can waste more power (8W instead of 0.5W) and have little or no delay in my macros.