Create README.md

Author: LuiCat

README.md

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+# ArduinoTaikoController
+
+Sketch for Arduino based taiko game controller circuit
+
+## Circuit Setup
+
+For most of the times, pluging the sensors directly into Arduino's analog pins will work.
+But for most of the times you'd better connect a resistor in parallel or an RC low-pass circuit for each sensor.
+
+For different types of sensors, you have to determine the amplitute of output level on arduino.
+By using a maximum reference voltage and enabling debug info you can see the input voltage level in 1/1024 of the reference voltage.
+Then you should choose a reference voltage wisely, using either pre-built 5V/1.1V or external voltage sources.
+
+## Algorithm
+
+This controller program uses a dynamic threshold of sensor input levels to trigger an input.
+Everytime a sensor gives a significantly higher input level, the algorithm sets the threshold of this sensor to that input level, and gradually lowers the threshold.
+To avoid picking up inputs from other sensors erroneously, when a sensor is recognized as triggered, the threshold level of all other sensors is raised as well.
+Also, a cooldown length will be added to all sensors so to ignore the unstable levels near a drum hit.
+
+## Parameters (with suggested values)
+
+#### min_threshold = 20
+The minimum level that a trigger is recognized for all sensors.
+
+To determine an optimal value for this level, try enabling debug info.
+Usually, this value is only used to ignore sensor noises, but you can use this level as a sensitivity level.
+
+#### cd_length = 8000
+The cooldown length of the triggered sensor, in microseconds (1x10^-6).
+
+While a sensor is in its cooldown period, no input will be generated for it, but the threshold level would still be updated.
+During the cooldown period, the corresponding key of the sensor is kept pressed. When it ended, the key is released.
+
+#### cd_antireso_length = 8000
+The cooldown length of sensors other than the triggered one, in microseconds.
+
+When there's a drum hit on one part of the drum, other parts will still have fluctuations in sensor levels.
+By using cooldown periods for sensors other than the triggered one, we are able to let these sensors settle down and also get their threshold level updated,
+so that there will not be any mistrigger after the cooldown period expires.
+
+#### k_antireso = 0.85
+How much the thresholds of every sensor other than the triggered one are raised to, in ratio to the threshold of the triggered sensor.
+
+#### k_decay = 0.96
+How fast every threshold level decays, in ratio.
+
+For approximately every millisecond the threshold is lowered by k_decay.
+
+#### pin[4] = {A3, A0, A2, A1}
+The analog input pins of four sensors.
+
+#### key[4] = {'d', 'f', 'j', 'k'}
+The key mapping of four sensors.
+
+## Debug Info
+
+If the macro ```DEBUG_OUTPUT``` is enabled, there will be debug info printed via serial. Take a look at your serial monitor.
+
+The first 4 rows indicates current vibration level of the four sensors, and the last 4 rows indicates the minimum level for a sensor to trigger a input;
+the symbols in the middle shows current status of the sensors, # for input triggered and * for anti-resonance state.
+
+A typical output could be:
+
+```
+0  3  13 63 |         | 0  0  0  0
+51 2  11 58 | * * * # | 53 53 53 63
+83 5  9  24 | # * * # | 83 70 70 70
+```
+