I have now got my 4x7 display with MAX7221 and LedControl.h to show four digits. I can't see how to display a decimal point. It doesn't need to move, just follow the second digit. The playground seems to just skate round this.
Thank you.
http://playground.arduino.cc/Main/LedControl
The setChar(addr,digit,value.dp)-function accepts a value of type char for the whole range of 7-bit ASCII encoding. Since the recognizable patterns are limited, most of the defined characters will be the -char. But there are quite a few characters that make sense on a 7-segment display.
Here is the set of printable characters:
0 1 2 3 4 5 6 7 8 9
A a (prints upper case)
B b (prints lower case)
C c (prints lower case)
D d (prints lower case)
E e (prints upper case)
F f (prints upper case)
H h (prints upper case)
L l (prints upper case)
P p (prints upper case)
- (the minus sign)
., (lights up the decimal-point)
_ (the underscore)
(the blank or space char)
Does that mean just a decimal point for that "digit" and nothing else, 1 2 . 3 vs 1 2. 3 ?
And well might you ask, for the answer may have nothing to do with that part of the article. I think what we have here is the same old situation which I first encountered in about 1967. If you want to find out how a programme works, you do not by choice ask the programmer.
What I want is the dp displayed just like anybody would expect - along with the digit, not exclusively.
The only programme with any practical use for ledControl.h that I have ever seen was picked up from here a couple of days ago. I have extended it to display four digits.
After all the conditioning to get the digits, the final print commands were
lc.setDigit(0,0,digit1,false);
lc.setDigit(0,1,digit2,false);
lc.setDigit(0,2,digit3,false);
lc.setDigit(0,3,digit4,false);
No amount of fartarsing about with dots and commas worked, but what does work is this
lc.setDigit(0,0,digit1,false);
lc.setDigit(0,1,digit2,false);
lc.setDigit(0,2,digit3,true);
lc.setDigit(0,3,digit4,false);
digit3 being units, followed by two decimal places, digit2 and digit1.
I guess I should carve it up in stone somewhere, if it isn't already.......
diligens improuida prodigia facit
Does that mean that you now have the decimal point with the numeral like you wanted?
I was thinking that you might have to use two character (numeral) sets, one with dp and the other without (similar to upper and lower case.)
Yes, the "eighth segment" is used on the relevant digit, so that it looks like what you would expect.
I was starting to regret this venture, as there seems to be little practical support for the 7221 but I now think something good will come of this.
Yes, I think that Robert Burns expressed it best in his poem,
"To a Library",
The best-laid schemes o' libraries an' men
Gang aft agley,
An' lea'e us nought but grief an' pain,
For promis'd joy!