help with propeller display.

[hemnath]

I'm using PIC 18F2520 and crystal 40 Mhz. Connected 8 LED's to uc PORT B. And, started programming.
But i want to display a character 'A' . I surfed and found some results. For Letter 'A', have to send many ascii values. Why is it so?
Also how do i calculate the ascii value for all characters and numbers.

- - - Updated - - -

i have found, how to calculate the ascii value for characters and for numbers.
but what should be the delay value ?

 

[paulfjujo]

hello,

if you not afrraid by french langage
have a lok on
**broken link removed**
or
**broken link removed** [...] clock.html

 

[betwixt]

The reason you have to send so many 'characters' is you have to draw the font itself. The numbers are the bits of a bitmapped shape rather than a command to produce a character. Propeller displays are usually scanned vertically so if your character font is 8 pixels high by 5 pixels wide you have to send 5 lots of 8 bit data to draw each column in turn.

Brian.

 

[hemnath]

Thank you for your help.
I had done the hardware and software. Please help whether i'm going on the right path.
I'm using CPU fan. I think it could be 3800 RPM. Calculated 1 degree of movement = 43.859 usec
using 12Mhz crystal and using Timer1. Calculated the timer TMRH and TMRL value for interrupt action to take place. 0xFF7C

Hardware is configured as, when uC pin is low, LED glows. so the vales below are calculated for only showing character 'A'
And in the main routine
output_b(0x81);
output_b(0x6F);
output_b(0x6F);
output_b(0x6F);
output_b(0x81);

But i doesn't shows the character 'A' when i power the fan and to the Board.
Do i have to use delay between every signal? what should be ?
Please help !!!

 

[betwixt]

You probably want to introduce a space after the character so they don't all blend together but the values you show are correct for an active low 'A'. You do need a short delay between each value because at 12MHz the time each is displayed might be too short to see. Perhaps you have a delay already in your 'output_b()' routine.

Next questions: what do you see at the moment? How are you synchronizing the fan rotation to the data?

Brian.

 

[paulfjujo]

hello,

as Betwitx said, the main key for this application, is synchronisation.
you must have a sensor to detect one point of the circonference
with define START time of all other calculations.
-how many caracteres do you want to display ?
-what matrix used for a charactere (5*7 or 6*8 or ?)
so,you can define pixel time
time for 1 rotation / (width of the matrix * nb of chars)
inside this pixel time ,you will display one colum of char
and so on...