Just a quick post on what happens when you miss the forest for the trees. I’ve been having trouble getting the MTCH6102 to work well with my touchpad setup. I was having trouble reading the TOUCHX,TOUCHY,TOUCHLSB registers and displaying them on the LCD.
At first I thought I wasn’t converting the values correctly, but that wasn’t it. The code below shows how to get an 8 bit and a 4 bit number into a twelve bit variable. This code is correct, if a bit wasteful.
uint16_t touchx,touchy; static volatile uint8_t buff,touchx_bf,touchy_bf; buff=twi_read(0x11); buff=twi_read(0x12); buff=twi_read(0x13); touchx=((buff << 4) | ((0xF0 & buff) >> 4)); touchy=((buff << 4) | ((0x0F & buff))); itoa(touchx,touchx_bf,10); itoa(touchy,touchy_bf,10);
Then I thought maybe I was running out of memory and overflowing. But there’s no reason to only have this happen when you touch a certain part of the touchpad (duh).
Then I though maybe there’s some kind of data corruption because of my bad layout, so I looked with my oscilloscope at SCL and SDA and manually decoded the values sent back and forth (that was fun). There was no data corruption. Turns out it was a PEBCAC.
Compare the first (incorrect) listing below with the second (correct) one and see if you can figure out what the problem was.
lcd_gotoxy(0,0); lcd_puts(touchx_bf); lcd_gotoxy(0,1); lcd_puts(touchy_bf);
lcd_gotoxy(0,0); lcd_puts(" "); lcd_gotoxy(0,0); lcd_puts(touchx_bf); lcd_gotoxy(0,1); lcd_puts(" "); lcd_gotoxy(0,1); lcd_puts(touchy_bf);
The goddamn LCD kept displaying part of the previous value and made it look like it was displaying 900 (for example) instead of 9. *FACEPALM*
Let this be a lesson to you kids: always clean your display, the smudges might drive you to premature hair loss.