How to plot a graph on Nokia 5110 LCD

Question

I have interfaced a Nokia 5110 LCD to a PIC. It displays characters using a font table.

Is there a way to plot ADC data on the LCD with ADC data on Y axis and time on X axis? I do not want to use a library as my code space is limited. I'm using Microchip XC8 compiler.

Answer 1

Save your samples into an array, then plot each ADC value as the y value, and increment the x value.

Something like the code below (int8_t = unsigned char typedef):

int8_t buffer[256];
int8_t i;

for(i = 0, i < 256, i++)
{
    // draw_pixel is your routine for plotting an individual pixel 
    draw_pixel(i, buffer[i]);
}

You can interpolate between the pixels if desired (you need a draw_line function - google for code), then do something like:

// note end value decremented by one to account for i+i
for(i = 0, i < 255, i++) 
{
    draw_line(i, buffer[i]), i+1, buffer[i+1]); 
}

Answer 2

I worked with the Nokia 5110 display a while ago but using a MSP430.

The display can be seen as an array of 84 columns x 6 blocks of 8 pixels each; writing a value from 0x00 to 0xFF to a block will change its contents (0x00 = nothing on that block, 0xFF = this block is fully on). Block 0 represents rows 0 to 7, block 1 represents rows 8 to 15 etc...

Thus you'll need a buffer of 84 x 6 = 504 values to hold those, since the display is write-only. To draw a pixel at (x,y) you need to find which block you want to write to, then change the adequate values on the buffer, set the display X/Y position to it and write it there.

Those codes for the Arduino might help: https://github.com/adafruit/Adafruit-PCD8544-Nokia-5110-LCD-library and https://github.com/adafruit/Adafruit-GFX-Library