Report by Guy Lee, last update 4/3/06
Unfortunately, the datasheet has poorly 2-page information. For more detail, I have to take a deeper look at Touch Screen Reference Desogn. In "Hardware Setup" chapter of this datasheet, I get an information which is likely what I needed for touch panel pins.
This picture shows how a touch panel connects to the evaluation board:
And here is the close look at the touch panel pins:
Because the LM8000 reference design comes with a 4-wire touch panel, which is said Panasonic EMU601A2 on website, and also, after taking a close look at the panel, I assume that some pins are useless.
Analog vs Digital
Left is digital touch panel which only senses ON/OFF mode and right one is what I get, Panasonic EMU601A2, which can also sense the pressure by resistive change.
Here is my circuit:
DEFINE OSC 4 ' Define ADCIN parameters ' Set number of bits in result DEFINE ADC_BITS 10 ' Set clock source (3=rc) DEFINE ADC_CLOCK 3 ' Set sampling time in microseconds DEFINE ADC_SAMPLEUS 10 TRISA = %11111111 ADCON1 = %10000010 tx var portc.6 rx var portc.7 n9600 con 16468 output portb.7 channel var byte adcVar var word xVar var word main high portb.7 for channel = 0 to 3 adcin channel, adcVar[channel] serout2 tx, n9600, ["porta.", DEC channel, "= ", DEC adcVar[channel], 9] ' pause 50 next 'xVar = abs(adcVar-adcVar) 'serout2 tx, n9600, [dec xVar,13] 'pause 1000 serout2 tx, n9600, [10,13] goto main
- It seeems that the numbers jump irregularly but do react to my touch. And the change seems to react to the pressure.
- I tried wheatstone bridge and aso ampifier, but they didnt help.