First decide how large the Image will be. What is the range of the value? Let’s say your value is a temperature between 32 and 100 degrees F. That’s a difference of 68. If you use a graph with one degree equal to one pixel then the resolution of the graph will be one degree and the graph will need to show 69 pixels. I used pixels because the display is based on pixels and to use other scale modes requires additional computations to resolve. If the final objective were to print the graph then it would be necessary to use a different scale mode.

Now the time base should be decided. Will the one minute cause the graph to move one pixel? Then how wide should the graph be? 60 pixels would be one hour.

To plot the points (readings), you would use the draw line function. You wold use the last point and the current point to draw the line. This will fill in any jumps in the value.

Line(OldValue,2)-(NewValue

OldValue = NewValue

Use the BitBlt to move the graph (chart). Move the Y starting at 0 and a width of one less than the width of the time base to position 1. This will shift the chart one pixel to the right. The column for Y=0 is blank. Think of this as the supply of blank chart paper.