TTL input - 3rd states possible?

[sougata]

Hi,

It is possible. Did you connect your PIC according to the schematic I provided. <img src="http://www.picbasic.co.uk/forum/attachment.php?attachmentid=1507&d=1175158348" align="absmiddle">Try increasing the pause. Please post your entire code and schematic. It is possible in one way or the other. I have chosen the Digital way. Detecting multiple switches with one pin is also possible using the ADC. By the way the circuit doesn't work when both the switches are pressed simultaneously. The 1K resistors are provided for that purpose so that you don't blow up your PS. When both are pressed most likely your PIC would read a logic high. As you get 1/2VDD and @ 5 volts it is good enough to be a logic 1. In any TTL/CMOS gate your cannot have anything other than 0 or 1 in your output whether your inout is at 0,1 or Z. So software tricks does it. By switching your port pin between input and output and detecting the holding capacitors state. I repeat please post your exact code and schematic and it should work.
Let me clarify my understanding about your requirement.

• You need to use only one pin of your PIC.
• You need to connect 2 switches to that.
• You need to determine whether your input is hanging idle (Z)
• Switch connected to VDD was pressed (H)
• Switch connected to VSS was pressed (L)

I am waiting.