I would be grateful if someone can explain this apparent contradiction. Obviously the code does work, and I'm just not seeing something. So how can this work? Those 2 bits should go to PH6,5 not PE1,0.įurthermore, PE1,0 are used for TXD and RXD, so those bits can't be used for the display. The shield uses the D9 and D8 pins for these bits, but they are connected to PH6 and PH5. This makes sense except for the two least significant data bits, which the code above is setting into port bits PE1 and PE0. This is done in the UTFT library for the MEGA board, using this code:. Therefore, code that writes to these shields must splatter the data bits to the appropriate AVR port bits, before strobing the shield's WR line. These pins don't connect to a single AVR 8 bit port, but are split amongst 2 or 3 ports. On these shields, the 8 data lines for bits 7.0 connect to Arduino pins D7.D2,D9,D8 on both UNO and MEGA. The animation given below shows Proteus simulation for variable duty cycle PWM signal from Arduino pin D10.I'm experimenting with TFT LCD display shields designed for UNOs, but which can alsoīe used with the MEGA 2560 board, and I'm confused by an apparent contradiction. PinMode(A0,INPUT) /* ser pin A0 as a input pin */ PinMode(pwm_pin,OUTPUT) /* set pin 10 as a output pin */ *two interger type variables to store digital value and duty cycle value */ This code generates 0-100% variable duty cycle with the default frequency of D10 pin of Arduino. Also, connect an oscilloscope to D10 of Arduino.Ī=analogRead(A0) /* take analog sample from A0 and store result in variable 'a'*/ī= map(a,0,1023,0,255) /* map the digital value to duty cycle range 0-255 */ĪnalogWrite(pwm_pin,b) /* generate pwm signal on pin10 with duty cycle value of b */ Make connections with Arduino and POT according to this schematic diagram. In other words, we will map the digital value measured with analogRead() function into duty cycle. To control duty cycle, we will use a potentiometer with analog channel zero of Arduino. We will use D10 pin of Arduino to get output signal. In this section, we will learn to generate variable duty cycle PWM. } Proteus Simulation Output Variable Duty Cycle PWM Arduino TCCR1B=_BV(WGM13)|_BV(CS11) /* Activate PWM Phase, frequency correction Mode */įloat frequency=0 /* initially set frequency to zero */ TCCR1A=_BV(COM1A1)|_BV(COM1B1) /* set Fast PWM Mode */ PinMode(outputpin, OUTPUT) /* set as a output put */ * Perform initialization and declarations inside setup() */ void loop()Ĭomplete Code int outputpin=9 /* Assign symbolic name outputpin to D9 PWM pin of Arduino */ The value of frequency gets updated on the PWM pin after every one second. The potentiometer which connects with analog channel zero (A0) of Arduino is used to control set the frequency of the PWM signal. 0.0113 is a factor that restricts the count variable in the range of 10000 to 100000 which results in a frequency range of 10 Hz to 100Hz. Similarly, analogRead() functions reads 0 when voltage is 0V. The analogRead() function reads 1023 when voltage is 5V at the analog pin. Inside the loop() function, the value of OCR1A is being calculated stepwise according to the required frequency formula given above.
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