I'm using a front-end of Lua which is unfortunately outdated, so I'm stuck with version 5.1 here, meaning the bit32 library is out of reach (which I probably could have used to convert this).
So I'm wondering if anyone knows of a way I could implement either a floating-point to binary (digits) function or, better yet, floating-point to hex. The best I've been able to come up with so far is a decimal to binary/hex function...
lua-MessagePack. A big thank you goes to him.
function float2hex (n) if n == 0.0 then return 0.0 end local sign = 0 if n < 0.0 then sign = 0x80 n = -n end local mant, expo = math.frexp(n) local hext = {} if mant ~= mant then hext[#hext+1] = string.char(0xFF, 0x88, 0x00, 0x00) elseif mant == math.huge or expo > 0x80 then if sign == 0 then hext[#hext+1] = string.char(0x7F, 0x80, 0x00, 0x00) else hext[#hext+1] = string.char(0xFF, 0x80, 0x00, 0x00) end elseif (mant == 0.0 and expo == 0) or expo < -0x7E then hext[#hext+1] = string.char(sign, 0x00, 0x00, 0x00) else expo = expo + 0x7E mant = (mant * 2.0 - 1.0) * math.ldexp(0.5, 24) hext[#hext+1] = string.char(sign + math.floor(expo / 0x2), (expo % 0x2) * 0x80 + math.floor(mant / 0x10000), math.floor(mant / 0x100) % 0x100, mant % 0x100) end return tonumber(string.gsub(table.concat(hext),"(.)", function (c) return string.format("%02X%s",string.byte(c),"") end), 16) end function hex2float (c) if c == 0 then return 0.0 end local c = string.gsub(string.format("%X", c),"(..)",function (x) return string.char(tonumber(x, 16)) end) local b1,b2,b3,b4 = string.byte(c, 1, 4) local sign = b1 > 0x7F local expo = (b1 % 0x80) * 0x2 + math.floor(b2 / 0x80) local mant = ((b2 % 0x80) * 0x100 + b3) * 0x100 + b4 if sign then sign = -1 else sign = 1 end local n if mant == 0 and expo == 0 then n = sign * 0.0 elseif expo == 0xFF then if mant == 0 then n = sign * math.huge else n = 0.0/0.0 end else n = sign * math.ldexp(1.0 + mant / 0x800000, expo - 0x7F) end return n end The float2hex in the example above returns an int. That being said if anyone needs it here is a intToHex conversion function that can be found in the lua archives (http://lua-users.org/lists/lua-l/2004-09/msg00054.html). I used the return value of the float2hex function above and fed it into this function. The output of intToHex is a string (Ex: 0xA4CD).
function intToHex(IN) local B,K,OUT,I,D=16,"0123456789ABCDEF","",0 while IN>0 do I=I+1 IN,D=math.floor(IN/B),math.mod(IN,B)+1 OUT=string.sub(K,D,D)..OUT end OUT = "0x" .. OUT return OUT end The issue I faced was trying to convert from the Hex back to a Float; You can use that tonumber(x, 16) to convert it in combination with "Error - Syntactical Remorse's" response. The string.sub is only there because my Modbus driver does not swap the bytes :)
function convertFloatSwapWord(number) -- number is string of format = 0x######## local x = 0 x = float2hex(number) x = intToHex(x) x = string.sub(x,5,6) .. string.sub(x,3,4) .. string.sub(x,9,10) .. string.sub(x,7,8) x = hex2float(tonumber(x, 16)) return x end