Two nights ago I managed to finally get the screen that shows graphs to draw the current temperature up in the corner on top of the graph.\u00a0 Most of the problem was figuring out how to convert the “float” numbers to characters.<\/p>\n
I needed to feed this into Microchip’s Graphics Library and accommodate “unicode” characters to get the “degree” symbol on the screen eventually.\u00a0 Instead of typing a string as string=”Hello There”; it ends up being string={‘H’, ‘e’, ‘l’, ‘l’, ‘l’, ‘o’, ‘ ‘, ‘T’, ‘h’, ‘e’, ‘r’, ‘e’}; which ends up being an array of character values.<\/p>\n
A float is a decimal number.\u00a0 In this case 3 digits for hundreds, a decimal position, and 3 more digits for numbers.\u00a0 The sensor is kicking out two digits and I’m adding readings together, averaging them, and then rounding up or down with the extra positions in some places.\u00a0 The PIC32 unfortunately does not have a floating point calculation area in its brain resulting in it “compensating” for it by automatically sliding all the other numbers around using complicated things called mantissa and a few other things I really don’t want to deal with.<\/p>\n
The reason I don’t want to deal with them is actually NOT because it is complicated (which it is) but because since it is compensating when you divide a float it has to do MANY cpu cycles for it to compensate and come up with the answer.\u00a0 It is ACTUALLY easier to multiply the float by 100, 1000, 10,000 etc and insert that number into an integer data type.\u00a0 Integers can be divided, multiplied, subtracted, etc without worrying about how the numbers line up and doing crazy compensating.\u00a0 They just don’t end up with a decimal.<\/p>\n
If you have a temperature of 175.25 degrees fahrenheit you multiply it by 1000 which equals 175250.\u00a0 This maintains all of\u00a0 required digits as a whole number and gives extra space for “rounding” down below.<\/p>\n
The issue with the graphics library you need to use a font for every character and take into consideration symbols like degrees etc.\u00a0 This means it is not simply just a “character” but you need to allocate for all the extra stuff.\u00a0 This results in a larger space for each character.\u00a0 To me it looks like a single character in XChar is actually two positions instead of one to leave extra room for the fancy characters to be allowed for.\u00a0 To convert text strings or float numbers into characters that can be handled by the library you have to load them into an array.\u00a0 This array to convert the above number (float averaged=175.25)\u00a0 looks something like this:<\/p>\n
int showtemp[8];
\nshowtemp[0]=averaged*1000; \/\/175250<\/p>\n
showtemp[1]=showtemp[0]\/100000; \/\/175250\/100000 = 1 in integer
\nshowtemp[2]=showtemp[0]\/10000-(showtemp[1]*10); \/\/175250\/10000 = 17.\u00a0 and then 17- 1*10 = 7 in integer
\nshowtemp[3]=showtemp[0]\/1000-(showtemp[1]*100)-(showtemp[2]*10); 175250\/1000 = 175 and then 175 – 1*100 – 7*10 = 5
\nshowtemp[4]=showtemp[0]\/100-(showtemp[1]*1000)-(showtemp[2]*100)-(showtemp[3]*10); \/\/ etc
\nshowtemp[5]=showtemp[0]\/10-(showtemp[1]*10000)-(showtemp[2]*1000)-(showtemp[3]*100)-(showtemp[4]*10);<\/p>\n
temperaturetext[0]=showtemp[1]+48; \/\/ 1 + 48 = 49 = proper number for 1 in character
\ntemperaturetext[1]=showtemp[2]+48;\u00a0 \/\/ 7+ 48 = 55 or proper number for 7 in character
\ntemperaturetext[2]=showtemp[3]+48; \/\/ etc
\ntemperaturetext[3]=46; \/\/ 46 = proper number for a decimal.
\ntemperaturetext[4]=showtemp[4]+48;\u00a0 \/\/etc
\ntemperaturetext[5]=showtemp[5]+48;\u00a0 \/\/etc<\/p>\n
<\/p>\n
the results in temperaturetext looks like {‘1′,’7′,’5′,’.’,’2′,’5′}<\/p>\n
I roasted twice now using the new graph with actual temperatures listed up top and was planning on comparing the results but I accidentally corrupted the first file.\u00a0 I’ve got one more batch of some coffee from Rwanda that I was testing with.\u00a0 I’m getting pretty close to running out of coffee again so it’s time to order some more soon.\u00a0 I was hoping to have something good from Ethiopia come up for sale but it’s still a little early for that.<\/p>\n
Still working on… recognizing temperatures for various(rough) stages the roast is at vs some sort of mechanism to confirm a stage marking things like first \/ second etc.\u00a0 Also need to get ambient weather information recorded and get other sensors going on it…. and make it pretier…. and of course get it hooked to higher voltage turning on and off the heat.<\/p>\n","protected":false},"excerpt":{"rendered":"
Two nights ago I managed to finally get the screen that shows graphs to draw the current temperature up in the corner on top of the graph.\u00a0 Most of the problem was figuring out how to convert the “float” numbers to characters. I needed to feed this into Microchip’s Graphics Library and accommodate “unicode” characters to get the “degree” symbol on the screen eventually.\u00a0 Instead of typing a string as string=”Hello There”; it ends up being string={‘H’, ‘e’, ‘l’, ‘l’, ‘l’, ‘o’, ‘ ‘, ‘T’, ‘h’, ‘e’, ‘r’, ‘e’}; which ends up being an array of character values. A float \u2026 Continue reading