Parse Byte into 8 Bits

Squirrel Code
1

I have code below that is pulling a byte from a modbus which I need to now get the bits MSB to LSB. I cannot seem to find a way to make that happen. The end result will I will know which but is On and which is Off. After this I will want to be able to write back but that is another day.

            function readbool(slv, from, numcoils, func) {
                local endaddress = (numcoils/8)-1;
                            local reqblob = blob();

                            /* Construct the request */
                            reqblob.writen(slv, 'b');                                                                                               // Slave address
                            reqblob.writen(func, 'b');                                                                                            // Function code
                            reqblob.writen(swap2(from), 'w');                                                          // Start address
                            reqblob.writen(swap2(endaddress), 'w');                                            // End address
                            reqblob.writen(crc16(reqblob), 'w');                      // CRC

                            /* Collaborate and listen */
                            local rspblob = this.dataTxRx(reqblob);
                            checkForException(rspblob, func);

                            rspblob.seek(2);
                            local numbytes = rspblob.readn('b');
                            if(numbytes != (numcoils/8)) {
                                            throw "Unexpected response length: " + numbytes + " != " + numcoils;
                            }
            
                            server.log("readbool " + numbytes);

                            rspblob.seek(3);
                            local valblob = rspblob.readblob(2*numcoils);
                            valblob.swap2();
                            local valarr = [];
                            for(local i = 0; i < numbytes; i++) {
                                            valarr.append(valblob.readn('b'));
                            }

                            return valarr;
            }
2

Probably not the most elegant, but how about doing a bitwise & with 0x01, then 0x02, then 0x04 and so on to 0x80.

Untested:
local mult=0x01; local bit = []; for (local i=0; i++; i<8) { bit.append(mult & byte); mult = mult << 1; }

3

Thanks, this was my attempt before I saw your note
rspblob.seek(3); // First byte of packed coil data in response
local valarr = [];
local b;
for(local i = 0; i < numcoils; i++) {
if(i % 8 == 0)
b = rspblob.readn(‘b’);
valarr.append((b >> (i % 8)) & 1);
server.log("bit loop " + ((b >> (i % 8)) & 1))
}

and this resulted in all zeros on the output which cannot be right. So either the blob is wrong or the bit conversion is bad.

4

Another option, harnessing the squirrel array api:

`
// "coils" is the byte you want to decode
// "result" is an array of boolean values

local mask=[0x80,0x40,0x20,0x10,0x08,0x04,0x02,0x01]
local result = mask.map(function(element,value=coils){
  return (element&value)>0 })`