Measure oscillator frequency of your device

Change Wire pointer to reference

Author: Bolukan

Adafruit_PWMServoDriver.cpp

@@ -30,16 +30,32 @@
 #include "Adafruit_PWMServoDriver.h"
 #include <Wire.h>
 
+/*!
+ *  @brief  Instantiates a new PCA9685 PWM driver chip with the I2C address on a
+ * TwoWire interface
+ */
+Adafruit_PWMServoDriver::Adafruit_PWMServoDriver():
+  _i2caddr(PCA9685_I2C_ADDRESS), _i2c(Wire) {
+}
+
+/*!
+ *  @brief  Instantiates a new PCA9685 PWM driver chip with the I2C address on a
+ * TwoWire interface
+ *  @param  addr The 7-bit I2C address to locate this chip, default is 0x40
+ */
+Adafruit_PWMServoDriver::Adafruit_PWMServoDriver(const uint8_t addr):
+  _i2caddr(addr), _i2c(Wire) {
+}
+
 /*!
  *  @brief  Instantiates a new PCA9685 PWM driver chip with the I2C address on a
  * TwoWire interface
  *  @param  addr The 7-bit I2C address to locate this chip, default is 0x40
- *  @param  i2c  A pointer to a 'Wire' compatible object that we'll use to
- * communicate with
+ *  @param  i2c  A reference to a 'TwoWire' object that we'll use to communicate
+ *  with
  */
-Adafruit_PWMServoDriver::Adafruit_PWMServoDriver(uint8_t addr, TwoWire *i2c) {
-  _i2c = i2c;
-  _i2caddr = addr;
+Adafruit_PWMServoDriver::Adafruit_PWMServoDriver(const uint8_t addr, TwoWire& i2c) :
+  _i2caddr(addr), _i2c(i2c) {
 }
 
 /*!
@@ -48,7 +64,7 @@ Adafruit_PWMServoDriver::Adafruit_PWMServoDriver(uint8_t addr, TwoWire *i2c) {
  *          Sets External Clock (Optional)
  */
 void Adafruit_PWMServoDriver::begin(uint8_t prescale) {
-  _i2c->begin();
+  _i2c.begin();
   reset();
   if (prescale) {
     setExtClk(prescale);
@@ -197,8 +213,8 @@ uint8_t Adafruit_PWMServoDriver::readPrescale(void)
  *  @return requested PWM output value
  */
 uint8_t Adafruit_PWMServoDriver::getPWM(uint8_t num) {
-  _i2c->requestFrom((int)_i2caddr, PCA9685_LED0_ON_L + 4 * num, (int)4);
-  return _i2c->read();
+  _i2c.requestFrom((int)_i2caddr, PCA9685_LED0_ON_L + 4 * num, (int)4);
+  return _i2c.read();
 }
 
 /*!
@@ -217,13 +233,13 @@ void Adafruit_PWMServoDriver::setPWM(uint8_t num, uint16_t on, uint16_t off) {
   Serial.println(off);
 #endif
 
-  _i2c->beginTransmission(_i2caddr);
-  _i2c->write(PCA9685_LED0_ON_L + 4 * num);
-  _i2c->write(on);
-  _i2c->write(on >> 8);
-  _i2c->write(off);
-  _i2c->write(off >> 8);
-  _i2c->endTransmission();
+  _i2c.beginTransmission(_i2caddr);
+  _i2c.write(PCA9685_LED0_ON_L + 4 * num);
+  _i2c.write(on);
+  _i2c.write(on >> 8);
+  _i2c.write(off);
+  _i2c.write(off >> 8);
+  _i2c.endTransmission();
 }
 
 /*!
@@ -263,17 +279,17 @@ void Adafruit_PWMServoDriver::setPin(uint8_t num, uint16_t val, bool invert) {
 }
 
 uint8_t Adafruit_PWMServoDriver::read8(uint8_t addr) {
-  _i2c->beginTransmission(_i2caddr);
-  _i2c->write(addr);
-  _i2c->endTransmission();
+  _i2c.beginTransmission(_i2caddr);
+  _i2c.write(addr);
+  _i2c.endTransmission();
 
-  _i2c->requestFrom((uint8_t)_i2caddr, (uint8_t)1);
-  return _i2c->read();
+  _i2c.requestFrom((uint8_t)_i2caddr, (uint8_t)1);
+  return _i2c.read();
 }
 
 void Adafruit_PWMServoDriver::write8(uint8_t addr, uint8_t d) {
-  _i2c->beginTransmission(_i2caddr);
-  _i2c->write(addr);
-  _i2c->write(d);
-  _i2c->endTransmission();
+  _i2c.beginTransmission(_i2caddr);
+  _i2c.write(addr);
+  _i2c.write(d);
+  _i2c.endTransmission();
 }

Adafruit_PWMServoDriver.h

@@ -75,7 +75,9 @@
  */
 class Adafruit_PWMServoDriver {
  public:
-  Adafruit_PWMServoDriver(uint8_t addr = PCA9685_I2C_ADDRESS, TwoWire *I2C = &Wire);
+  Adafruit_PWMServoDriver();
+  Adafruit_PWMServoDriver(const uint8_t addr);
+  Adafruit_PWMServoDriver(const uint8_t addr, TwoWire& i2c);
   void begin(uint8_t prescale = 0);
   void reset();
   void sleep();
@@ -90,8 +92,7 @@ class Adafruit_PWMServoDriver {
 
  private:
   uint8_t _i2caddr;
-  
-  TwoWire *_i2c;
+  TwoWire& _i2c;
 
   uint8_t read8(uint8_t addr);
   void write8(uint8_t addr, uint8_t d);

examples/gpiotest/gpiotest.ino

@@ -24,7 +24,7 @@ Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver();
 // you can also call it with a different address you want
 //Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver(0x41);
 // you can also call it with a different address and I2C interface
-//Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver(0x40, &Wire);
+//Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver(0x40, Wire);
 
 void setup() {
   Serial.begin(9600);

examples/oscillator/oscillator.ino

@@ -0,0 +1,129 @@
+/***************************************************
+  This is an example for our Adafruit 16-channel PWM & Servo driver
+  to calibrate the frequency of the oscillator clock of the PCA9685.
+
+  CAUTION: DO NOT CONNECT ANY VOLTAGE HIGHER THAN THE BOARD LIMITS.
+  For 3.3V boards, like the ESP8266, remove any 5V input. The setup will
+  feed the voltage back into the board to measure the frequency.
+  KABOEM, SMOKE if you use too much VOLTAGE.
+
+  Connect the PCA9685 with I2C (Ground, VCC, SCL, SCA) and apply
+  voltage on V+. See above not higher than board limits.
+  Connect the signal (yellow pin, PWM) of the PCA9685 to your board:
+  Default is pin 3, last of first block.
+  Default is pin 14 (of your ESP8266).
+
+  Formula for prescale to get the targetted frequency (=update_rate) is:
+  prescale = round ( osc_clock / 4096 * update_rate) - 1
+  rewritten: osc_clock = (prescale + 1) * 4096 * update_rate
+  We will measure the real update_rate to assert the real osc_clock.
+
+  ***************************************************/
+
+#include <Wire.h>
+#include <Adafruit_PWMServoDriver.h>
+
+// called this way, it uses the default address 0x40
+Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver(0x40, Wire);
+// you can also call it with a different address you want
+//Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver(0x40);
+// you can also call it with a different address and I2C interface
+//Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver(0x40, Wire);
+
+#if (defined(ESP8266) || defined(ESP32))
+
+// Applied frequency in the test: can be changed to get the optimal
+// oscillator calibration for your targetted frequency.
+#define FREQUENCY             50
+
+// CAUTION: ONLY CONNECT server and ESP WITHOUT 5V ON V+ or green breakout supply pins. Use 3.3V on V+
+#define PIN_SERVO_FEEDBACK     3 // Connect Yellow PWM pin, 3 = last on first block
+#define PIN_BOARD_FEEDBACK    14 // 14 => D5 on NodeMCU
+
+uint8_t prescale = 0;
+// loop
+#define INTERVAL   1000  // 1 sec
+int32_t lastEvaluation = 0;
+uint16_t frozenCounter = 0;
+uint16_t countDeviations = 0;
+
+uint32_t totalCounter = 0;
+uint32_t totalTime = 0;   // in millis
+uint32_t realOsciFreq = 0;
+uint32_t multiplier = 4096;
+
+// interrupt
+volatile uint16_t interruptCounter = 0;
+
+ICACHE_RAM_ATTR void handleInterrupt() {
+  interruptCounter++;
+}
+
+void setup() {
+  Serial.begin(115200);
+  Serial.println("PCA9685 Oscillator test");
+
+  // set PCA9685
+  pwm.begin();
+  pwm.setPWMFreq(FREQUENCY);             // Set some frequency
+  pwm.setPWM(PIN_SERVO_FEEDBACK,0,2048); // half of time high, half of time low
+  prescale = pwm.readPrescale();         // read prescale
+  Serial.printf("Target frequency: %u\n", FREQUENCY);
+  Serial.printf("Applied prescale: %u\n", prescale);
+
+  // prepare interrupt on ESP pin
+  pinMode(PIN_BOARD_FEEDBACK, INPUT);
+  attachInterrupt(digitalPinToInterrupt(PIN_BOARD_FEEDBACK), handleInterrupt, RISING);
+
+  // take a breath and reset to zero
+  delay(10);
+  interruptCounter = 0;
+  lastEvaluation = millis();
+}
+
+void loop() {
+  if (millis() - lastEvaluation > INTERVAL)
+  {
+    // first freeze counters and adjust for new round
+    frozenCounter = interruptCounter; // first freeze counter
+    interruptCounter -= frozenCounter;
+    lastEvaluation += INTERVAL;
+
+    totalCounter += frozenCounter;
+    totalTime += 1;
+
+    // only print deviations from targetted frequency
+    //if (frozenCounter != FREQUENCY)
+    {
+       multiplier = 4096;
+       realOsciFreq = (prescale + 1) * totalCounter; // first part calcutlation
+       // now follows an ugly hack to have maximum precision in 32 bits
+       while (((realOsciFreq & 0x80000000) == 0) && (multiplier != 1))
+       {
+          realOsciFreq <<= 1;
+          multiplier >>= 1;
+       }
+       realOsciFreq /= totalTime;
+       if (multiplier) realOsciFreq *= multiplier;
+
+       countDeviations++;
+       Serial.printf("%4u", countDeviations);
+       Serial.printf(" Timestamp: %4u ", totalTime);
+       Serial.printf(" Freq: %4u ", frozenCounter);
+       Serial.printf(" Counter: %6u ", totalCounter);
+       Serial.printf(" calc.osci.freq: %9u\n",realOsciFreq);
+    }
+  }
+
+}
+#else
+
+void setup() {
+  Serial.begin(115200);
+  Serial.println("PCA9685 Oscillator test");
+  Serial.println("yet not available for your board."); // please help adapt the code!
+}
+
+void loop() {}
+
+#endif // ESP8266/ESP32

examples/pwmtest/pwmtest.ino

@@ -24,7 +24,7 @@ Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver();
 // you can also call it with a different address you want
 //Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver(0x41);
 // you can also call it with a different address and I2C interface
-//Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver(0x40, &Wire);
+//Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver(0x40, Wire);
 
 void setup() {
   Serial.begin(9600);

examples/servo/servo.ino

@@ -25,7 +25,7 @@ Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver();
 // you can also call it with a different address you want
 //Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver(0x41);
 // you can also call it with a different address and I2C interface
-//Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver(0x40, &Wire);
+//Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver(0x40, Wire);
 
 // Depending on your servo make, the pulse width min and max may vary, you 
 // want these to be as small/large as possible without hitting the hard stop