46 lines
1.9 KiB
C
46 lines
1.9 KiB
C
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#ifndef ROWDELAY_H
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#define ROWDELAY_H
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#include <Arduino.h>
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#include <inttypes.h>
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/* RowDelay() delay's scan to give switches time to debounce.
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For fastest response time, RowDelay() should be placed before scan() or after pressRelease()
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(RowDelay() between scan and send would unnecessarily delay send).
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DELAY_MICROSECONDS explained
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----------------------------
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A keyboard with a faster scan rate responds faster.
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Follow these step to tune DELAY_MICROSECONDS for maximum scan rate for a given SAMPLE_COUNT:
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Initialize DELAY_MICROSECONDS in your sketch:
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const unsigned int RowDelay::DELAY_MICROSECONDS = 1000;
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Add this to the sketch's loop() function:
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debug.print_microseconds_per_scan();
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Compile and load the sketch into the microcontroller; microseconds_per_scan is printed every second.
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Adjust the value of DELAY_MICROSECONDS and repeat until:
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debug.print_microseconds_per_scan() <= DEBOUNCE_TIME / SAMPLE_COUNT
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DEBOUNCE_TIME can be obtained from the switch's datasheet. Some switch bounce times are:
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Cherry MX specifies 5msec bounce time http://www.cherrycorp.com/english/switches/key/mx.htm
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hasu measured Cherry MX bounce times .3ms to 1.4ms http://geekhack.org/index.php?topic=42385.0
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Tactile switch MJTP series bounce 10 ms http://www.apem.com/files/apem/brochures/MJTP_6MM.pdf
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Avoid sampling the switch input at a rate synchronous to events in the environment
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that might create periodic EMI. For instance, 50 and 60 Hz.
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The largest allowable DELAY_MICROSECONDS is 65535 (.065535 seconds).
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Polling I2C may slow the scan rate enough so that no additional delay is needed:
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const unsigned int RowDelay::DELAY_MICROSECONDS = 0;
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DELAY_MICROSECONDS is static so multiple row types can share it.
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For example, primary and secondary matrices would share the same DELAY_MICROSECONDS.
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*/
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class RowDelay
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{
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private:
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static const unsigned int DELAY_MICROSECONDS; //delay between each Row scan for debouncing
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public:
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void delay();
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};
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#endif
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