MidPoint Circle Formula

[kent_twt4]

This is a port of Midpoint Circle formula discussed in a previous post. Please don't ask me to explain, too far removed from doing the maths. And here is an example:

'Midpoint Circle algorithm
'Chip model
#chip 16f1783,8
#include <GLCD.h>

#define GLCD_RW  PortA.1     'Read/Write pin connection
#define GLCD_RESET  PortA.5  '‘Reset pin connection
#define GLCD_CS1  PortA.4    'Swap CS1/CS2 pin connections
#define GLCD_CS2  PortA.3
#define GLCD_RS  PortA.0     'RS pin connection
#define GLCD_ENABLE  PortA.2 'Enable pin Connection
#define GLCD_DB0  PortC.0    'Data pin 0 Connection
#define GLCD_DB1  PortC.1    'Data pin 1 Connection
#define GLCD_DB2  PortC.2    'Data pin 2 Connection
#define GLCD_DB3  PortC.3    'Data pin 3 Connection
#define GLCD_DB4  PortC.4    'Data pin 4 Connection
#define GLCD_DB5  PortC.5    'Data pin 5 Connection
#define GLCD_DB6  PortC.6    'Data pin 6 Connection
#define GLCD_DB7  PortC.7    'Data pin 7 Connection

dir PortA out
dir PortC out

dim  xradius, yordinate , radiusErr as Integer
InitGLCD

Start:
GLCDCLS
Set GLCD_CS1 Off        'Temporary Pset bug in glcd.h
Set GLCD_CS2 Off
wait 1 s
GLCDCircle (64,32,5,0)
GLCDCircle (64,32,10,0)
GLCDCircle (64,32,20,0)
GLCDCircle (64,32,31,0)
wait 10 s
goto start

sub GLCDCircle (xoffset, yoffset, xradius, yordinate)
'radiusErr = 1 - xradius
radiusErr = -(xradius/2)
Do While xradius >=  yordinate
   Pset ((xoffset + xradius), (yoffset + yordinate), on)
   Pset ((xoffset + yordinate), (yoffset + xradius), on)
   Pset ((xoffset - xradius), (yoffset + yordinate), on)
   Pset ((xoffset - yordinate), (yoffset + xradius), on)
   Pset ((xoffset - xradius), (yoffset - yordinate), on)
   Pset ((xoffset - yordinate), (yoffset - xradius), on)
   Pset ((xoffset + xradius), (yoffset - yordinate), on)
   Pset ((xoffset + yordinate), (yoffset - xradius), on)
   yordinate ++
   If radiusErr < 0 Then
      radiusErr = radiusErr + 2 * yordinate + 1
   else
      xradius --
      radiusErr = radiusErr + 2 * (yordinate - xradius + 1)
   end if
Loop
end sub

[kent_twt4]

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