2

I am trying to convert the following code to output to pin 7 (PH4, OC4B) on an Arduino Mega. The code outputs to pin 6. This code is from a GitHub for the GRBL on the Mega "https://github.com/fra589/grbl-Mega-5X" out of the cpu_map.h It is clear that PH6 and PH7 are on the same PORTH but I just do not know what bits need changing to get GRBL to output on pin 7.Any help would be welcome.

#elif defined (SPINDLE_PWM_ON_D6)

// Set Timer up to use TIMER4C which is attached to Digital Pin 6 - Ramps Servo 2
#define SPINDLE_PWM_MAX_VALUE     255.0 // Translates to about 1.9 kHz PWM frequency at 1/8 prescaler
#ifndef SPINDLE_PWM_MIN_VALUE
  #define SPINDLE_PWM_MIN_VALUE   1   // Must be greater than zero.
#endif
#define SPINDLE_PWM_OFF_VALUE     0
#define SPINDLE_PWM_RANGE         (SPINDLE_PWM_MAX_VALUE-SPINDLE_PWM_MIN_VALUE)

//Control Digital Pin 6 which is Servo 2 signal pin on Ramps 1.4 board
#define SPINDLE_TCCRA_REGISTER    TCCR4A
#define SPINDLE_TCCRB_REGISTER    TCCR4B
#define SPINDLE_OCR_REGISTER      OCR4A
#define SPINDLE_COMB_BIT          COM4A1

// 1/8 Prescaler, 16-bit Fast PWM mode
#define SPINDLE_TCCRA_INIT_MASK (1<<WGM41)
#define SPINDLE_TCCRB_INIT_MASK ((1<<WGM42) | (1<<WGM43) | (1<<CS41))
#define SPINDLE_OCRA_REGISTER   ICR4 // 8-bit Fast PWM mode requires top reset value stored here.
#define SPINDLE_OCRA_TOP_VALUE  0xFF // PWM counter reset value. Should be the same as PWM_MAX_VALUE in hex.

// Define spindle output pins.
#define SPINDLE_PWM_DDR   DDRH
#define SPINDLE_PWM_PORT  PORTH
#define SPINDLE_PWM_BIT   3 // MEGA2560 Digital Pin 6
jsotola
  • 1,554
  • 2
  • 12
  • 20
Mr.Spriggs
  • 21
  • 1

1 Answers1

1

You want to replace pin 6 (PH3, OC4A) with pin 7 (PH4, OC4B). There are three things you have to change. First, the output compare register, which is OCR4A for pin OC4A and OCR4B for pin OC4B. Thus:

-#define SPINDLE_OCR_REGISTER      OCR4A
+#define SPINDLE_OCR_REGISTER      OCR4B

Then, the configuration bit that enables the output:

-#define SPINDLE_COMB_BIT          COM4A1
+#define SPINDLE_COMB_BIT          COM4B1

Last, the bit to set in the data direction register, which is 3 for PH3 and 4 for PH4:

-#define SPINDLE_PWM_BIT   3 // MEGA2560 Digital Pin 6
+#define SPINDLE_PWM_BIT   4 // MEGA2560 Digital Pin 7

Note: as in diff -u format, the prefix - means “remove this”, the prefix + means “add this”.

Edgar Bonet
  • 45,094
  • 4
  • 42
  • 81