I am interfacing a radio receiver to an Arduino. There is a node in the receiver squelch circuit that switches when the receiver detects a RF carrier. No-signal voltage is 7.77V, and it switches (rather slowly, with some jitter) to 4.22V when a RF signal is received. It is a high-Z node, so I cant load it without buffering, likely not more than a few uA.
I want to convert this to a logic level for an Arduino input port pin, using a Schmitt Trigger level-shifter to eliminate multiple transitions with about 100mV of hysteresis. The trip points should be ~ 7.0V and 6.9V. The voltage levels at the Arduino pin should be near 0V and near 5V, not over 5.3V, logic polarity not important because it is trivial to invert the logic later...
Arduino is powered with 5.0V. The radio is powered with 9.0V, so either or both of these well-regulated supplies are available to power the Schmitt Trigger.
I have some ideas, but I'd like some suggestions from the forum for a stable circuit with a low parts count...
I want to convert this to a logic level for an Arduino input port pin, using a Schmitt Trigger level-shifter to eliminate multiple transitions with about 100mV of hysteresis. The trip points should be ~ 7.0V and 6.9V. The voltage levels at the Arduino pin should be near 0V and near 5V, not over 5.3V, logic polarity not important because it is trivial to invert the logic later...
Arduino is powered with 5.0V. The radio is powered with 9.0V, so either or both of these well-regulated supplies are available to power the Schmitt Trigger.
I have some ideas, but I'd like some suggestions from the forum for a stable circuit with a low parts count...