Thanks for the reply.Hi, and welcome to AAC.
I might be wrong, but...
1) Use transistors on each output as a switch. Then you'll need some extra circuitry.
2) Use the atmega16 ADC function, and read the voltage with analogRead. With this option I do not think you need any additional circuitry.
What you are observing does not match the datasheet. If the behavior of the chip does not match the datasheet there is literally nothing you can do about it, except find a chip that does. Since this is an obsolete chip, it is unlikely that you obtained it from a reputable source. You either need to find a working chip or come up with an alternate solution.Actually I need different 4-bits values i.e (Q1, Q2, Q3 Q4) output of the cm8870 and perform specific task as per the output through the micro controller. But due to low voltage its not detecting 1. for example the output is Q4(0), Q3(1), Q2(0) Q1(0) 1 corresponds to 2v and 0 corresponds to 0V. But to perform a specific task the microcontroller is detection all those inputs as 0. Because it will not detect 1 unless it is close to 3v or higher.
Using ADC I will get only one value. also I can connect only one of the Q1, Q2, Q3 Q4. as Vref.
What you are observing does not match the datasheet. If the behavior of the chip does not match the datasheet there is literally nothing you can do about it, except find a chip that does. Since this is an obsolete chip, it is unlikely that you obtained it from a reputable source. You either need to find a working chip or come up with an alternate solution.
Looks like you lifted the circuit directly from the California Micro devices data sheet, so I won't ask you about the circuit. Only thought would be to confirm that Vcc is actually at 5.0 v during operation.
the StD just goes high whenever a valid dtmf tone is detected and the output pins are latched to the 4-bits binary. Or say it keeps blinking till u send a dtmf tone.If you connected a LED directly to the output it is likely you damaged the chip. You said you changed the chip and it behaves the same. Seems like what you have is a bunch of chips that do not work for one reason or another. What is the purpose of the signal labeled StD? Could it be a Data Strobe? Would you ever expect the data outputs to be High-Impedance or Tri-Stated? How about showing us the full circuit instead of some cartoon version.
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