kneeAngleDataLogger.ino

#include <arduino-timer.h>

int pinA = 4; // Pin for Encoder Channel A.
int pinB = 2; // Pin for Encoder Channel B.

bool oldA; // Old Encoder Channel A signal.
bool oldB; // Old Encoder Channel B signal.

bool newA; // New Encoder Channel A signal.
bool newB; // New Encoder Channel B signal.

float numDegrees = 0; // Current knee angle (relative — incremental encoder) (0.5° resolution).

// strDegrees = "±XXX.X\n"
char strDegrees[7]; // charsPerMessage = 7

int bitsPerSecond = 9600; // Default baud (data transfer) rate.
// Reliable over Bluetooth.

\(\small \; \vdots\)

\(\small \: \bullet \quad \quad \text{bits per second} = 9\,600\)

\(\small \: \bullet \quad \quad \text{start bits per character} = 1\)

\(\small \: \bullet \quad \quad \; \! \text{data bits per character} = 8\)

\(\small \: \bullet \quad \quad \: \text{stop bits per character} = 1\)

\(\small \: \bullet \quad \quad \text{bits per character} = ( \text{start bits} + \text{data bits} + \text{stop bits} ) \ \text{per character} = 10\)

\(\small \: \bullet \quad \quad \text{seconds per character ($\,T_\textsf{character}$)} = \text{bits per character} \: / \: \text{bits per second} \approx 0.001\,04\)

\(\small \: \bullet \quad \quad \text{characters per message} = 7\)

\(\small \: \bullet \quad \quad \text{seconds per message ($\,T_\textsf{message}$)} = \text{seconds per character} \, \cdot \: \text{characters per message} \approx 0.007\,3\)

\(\small \: \bullet \quad \quad \text{milliseconds per message} = \lceil \, \text{seconds per message} \: \cdot \, 10^3 \, \rceil = \lceil \, 7.3 \, \rceil = 8 \longrightarrow \boxed{10}\)

\(\small \; \vdots\)

/*
 * int startBitsPerChar = 1;
 * int  dataBitsPerChar = 8;
 * int  stopBitsPerChar = 1;
 *
 * int bitsPerChar = startBitsPerChar + dataBitsPerChar + stopBitsPerChar;
 *
 * float secondsPerChar = bitsPerChar / bitsPerSecond;
 *
 * int charsPerMessage = 7;
 *
 * float secondsPerMessage = secondsPerChar * charsPerMessage;
 *
 * int millisPerMessage = ceil(secondsPerMessage * 1e3);
 *
 */

int millisPerMessage = 10;

Timer<1, millis, char *> timer;

void setup()
{
    pinMode(pinA, INPUT_PULLUP);
    pinMode(pinB, INPUT_PULLUP);
    pinMode(5,    INPUT_PULLUP);

    oldA = digitalRead(pinA);
    oldB = digitalRead(pinB);

    Serial.begin(bitsPerSecond);

    timer.every(millisPerMessage, [](char *strDegrees) -> bool { Serial.println(strDegrees); return true; }, strDegrees);
}
void loop()
{
    if (digitalRead(5))
    {
        timer.tick();
    }

    dtostrf(numDegrees, 3, 1, strDegrees);

    newA = digitalRead(pinA);
    newB = digitalRead(pinB);

    if ((!oldA && newB || oldA && !newB) &&
    (!oldB && !newA || oldB && newA))
    {
        numDegrees += 0.5;
    }
    if ((oldA && newB || !oldA && !newB) &&
    (!oldB && newA || oldB && !newA))
    {
        numDegrees -= 0.5;
    }
    oldA = newA;
    oldB = newB;
}

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