Method and apparatus for input cable length indication for SDI signals
View Patent ↗A technique for indicating an input cable length includes measuring within a cable equalizer circuit a differential voltage that varies approximately linearly in proportion to cable length. The measured voltage is translated into a cable length measurement corresponding to the connected input cable. The translated input cable length measurements can be provided on a graphical user interface (GUI) in the form of a graphical representation and/or numerical value.
1. A method for indicating an input cable length comprising:
measuring a voltage differential on input equalizers, wherein the voltage differential varies between first and second values approximately linearly in proportion to the input cable length;
translating the measured differential voltage into a cable length measurement;
performing a calibration using a first measurement for a minimum length cable and a second measurement for a maximum length cable prior to translating the measured differential voltage into a cable length measurement, wherein the measured differential voltage is translated into a cable length measurement by performing a linear approximation based on the first measurement and the second measurement; and
displaying a representation of the measured cable length.
2. The method according to claim 1 , wherein said translating comprises interpolating between a minimum and maximum voltage values corresponding to a minimum and maximum cable lengths.
3. The method according to claim 1 , wherein the first and second values correspond to −1 Volt and +1 Volt, respectively.
4. The method of claim 1 , further comprising displaying a numerical representation of the measured cable length.
5. The method of claim 1 , wherein the input equalizers are operably coupled to at least one input port of an adaptive cable equalizer circuit, wherein the measuring includes measuring a differential voltage change resulting from a connection of the input cable to the at least one input port.
6. The method of claim 5 , wherein when the input port receives a signal from the input cable, the adaptive cable equalizer circuit generates a voltage.
7. The method of claim 1 , wherein the voltage differential comprises an ACC voltage differential.
8. The method of claim 1 , wherein the input cable comprises a serial digital interface (SDI) cable.
9. The method of claim 1 , further comprising:
calibrating between a minimum and maximum cable length prior to performing the measurement.
10. The method of claim 1 , further comprising:
converting the voltage differential to a digital value that interpolated to estimate the input cable length.
11. The method of claim 1 , wherein the voltage differential is measured for a serial digital interface (SDI) signal.
12. The method of claim 1 , wherein the voltage differential is measured between two lines of the equalizer.
13. The method of claim 12 , wherein the voltage differential is measured between two pins of an integrated circuit comprising the equalizer.
14. The method of claim 1 , wherein displaying a representation of the measured cable length comprises:
displaying a graphical user interface showing both a graphical illustration and numerical representation of the measured cable length.
15. An apparatus for indicating an input cable length comprising:
means for measuring a voltage differential on input equalizers, wherein the voltage differential varies between first and second values approximately linearly in proportion to the input cable length;
means translating the measured differential voltage into a cable length measurement;
means for performing a calibration using a first measurement for a minimum length cable and a second measurement for a maximum length cable prior to translating the measured differential voltage into a cable length measurement, wherein the measured differential voltage is translated into a cable length measurement by performing a linear approximation based on the first measurement and the second measurement; and
means for displaying a representation of the measured cable length.
16. The apparatus according to claim 15 , wherein the measuring means includes an analog-to-digital converter configured to convert the voltage differential to a digital value that interpolated to estimate the input cable length.
17. The apparatus according to claim 15 , wherein said means for graphically displaying comprises a display screen having a graphical user interface and an indicator for showing the determined cable length both graphically and numerically on the display screen.
18. The apparatus of claim 15 , further comprising:
means for displaying a numerical representation of the measured cable length.
19. The apparatus of claim 15 , wherein the means for measuring a differential comprise input equalizers operably coupled to at least one input port of an adaptive cable equalizer circuit, wherein the measuring includes measuring a differential voltage change resulting from a connection of the input cable to the at least one input port.
20. The apparatus of claim 19 , wherein when the input port receives a signal from the input cable, the adaptive cable equalizer circuit generates a voltage.
21. The apparatus of claim 15 , wherein the voltage differential comprises an ACC voltage differential.