Sensors, autonomous sensors and related systems, methods and devices
Disclosed embodiments relate to sensing states and changes of states of a signal and sensors for the same, including but not limited to, autonomous sensors. Such sensor may include an analog signal threshold detection circuit, a state detection circuit, and a measurement circuit. The analog signal threshold detection circuit may be configured to alternately assert and de-assert a threshold detected indication in response to an input signal and a state thereof. The state detection circuit may be configured to generate a signal state indication about a state of the input signal. The measurement circuit may be configured to generate a measurement in response to assertions of the threshold detected indication and the signal state indication, such as a count, a slew rate, or a frequency. In some embodiments, disclosed sensors may have programmable thresholds for sensing the signal states and changes therein.
1. A sensor, comprising:
a state detection circuit to generate a signal state indication about a state of an observed signal;
an analog signal threshold detection circuit to alternately assert and de-assert a threshold detected indication responsive to the observed signal and the signal state indication; and
a measurement circuit to generate a measurement responsive to assertions and de-assertions of the threshold detected indication and the signal state indication, wherein the measurement circuit comprises:
a start/stop logic to alternately generate a start signal or a stop signal responsive to the threshold detected indication and the signal state indication; and
a counter to increment a count during a time defined between a generated start signal and a generated stop signal.
2. The sensor of claim 1 , wherein the state detection circuit is to generate the signal state indication responsive to assertions and de-assertions of the threshold detection indication and a previous state of the observed signal.
3. The sensor of claim 1 , wherein the counter is to increment the count responsive to a countable element, the countable element including one of: a clock cycle, a rising edge of a clock, or a falling edge of a clock.
4. The sensor of claim 1 , wherein the measurement is one of the count, a slew rate, or a frequency.
5. The sensor of claim 1 , wherein the measurement circuit comprises a rising or falling edge indicator.
6. The sensor of claim 1 , further comprising an upper signal threshold register and a lower signal threshold register.
7. The sensor of claim 6 , wherein the upper and lower signal threshold registers are respectively coupled to the analog signal threshold detection circuit.
8. The sensor of claim 1 , further comprising a measurement register.
9. The sensor of claim 8 , wherein the measurement register is coupled to the measurement circuit.
10. A method, comprising:
selecting a first reference signal responsive to an indicated signal state of an observed signal being a first signal state;
observing a first relationship between a signal level of the observed signal and a signal level of the first reference signal;
setting the indicated signal state of the observed signal to a second signal state responsive to a previously indicated signal state and the observed first relationship between the signal level of the observed signal and the signal level of the first reference signal, the second signal state different than the first signal state;
starting a counter responsive to the indicated signal state of the observed signal being the second signal state;
selecting a second reference signal responsive to the indicated signal state of the observed signal being the second signal state;
observing a second relationship between the signal level of the observed signal and a signal level of the second reference signal;
setting the indicated signal state of the observed signal to the first signal state responsive to the previously indicated signal state and the observed second relationship between the signal level of the observed signal and the signal level of the second reference signal;
stopping the counter responsive to the indicated signal state of the observed signal being the first signal state; and
storing a measurement of the observed signal responsive to a transition time between observing the first relationship and the second relationship indicated by a value of the counter.
11. The method of claim 10 , wherein the observed signal is a discrete signal.
12. The method of claim 10 , providing a first and second fixed-level reference signals as the first reference signal and the second reference signal, respectively.
13. The method of claim 10 , further comprising:
determining states of the observed signal responsive to previous states of the observed signal and indications of relationships between signal levels of the observed signal and signal thresholds; and
providing a signal state indication associated with the observed signal responsive to the determined states of the observed signal.
14. The method of claim 13 , further comprising detecting an initial state of the observed signal.
15. The method of claim 13 , further comprising receiving values for the signal thresholds.
16. A computing system, comprising:
a processor; and
a memory storage having thereon machine-executable code adapted to permanently configure logic circuitry of the processor to:
select a first reference signal responsive to an indicated signal state of an observed signal being a first signal state;
observe a first relationship between a signal level of the observed signal and a signal level of the first reference signal;
set the indicated signal state of the observed signal to a second signal state responsive to a previously indicated signal state and the observed first relationship between the signal level of the observed signal and the signal level of the first reference signal, the second signal state different than the first signal state;
start a counter responsive to the indicated signal state of the observed signal being the second signal state;
select a second reference signal responsive to the signal state of the observed signal being the second signal state;
observe a second relationship between the signal level of the observed signal and a signal level of the second reference signal;
set the indicated signal state of the observed signal to the first signal state responsive to the previously indicated signal state and the observed second relationship between the signal level of the observed signal and the signal level of the second reference signal;
stop the counter responsive to the indicated signal state of the observed signal being the first signal state; and
store a measurement of the observed signal responsive to a transition time between observing the first relationship and the second relationship indicated by a value of the counter.