power_mgt.cpp

#include "FastLED.h"
#include "power_mgt.h"

//// POWER MANAGEMENT

// These power usage values are approximate, and your exact readings
// will be slightly (10%?) different from these.
//
// They were arrived at by actually measuing the power draw of a number
// of different LED strips, and a bunch of closed-loop-feedback testing
// to make sure that if we USE these values, we stay at or under
// the target power consumption.
// Actual power consumption is much, much more complicated and has
// to include things like voltage drop, etc., etc.
// However, this is good enough for most cases, and almost certainly better
// than no power management at all.
//
// You're welcome to adjust these values as needed; there may eventually be an API
// for changing these on the fly, but it saves codespace and RAM to have them
// be compile-time constants.

static const uint8_t gRed_mW   = 16 * 5; // 16mA @ 5v = 80mW
static const uint8_t gGreen_mW = 11 * 5; // 11mA @ 5v = 55mW
static const uint8_t gBlue_mW  = 15 * 5; // 15mA @ 5v = 75mW
static const uint8_t gDark_mW  =  1 * 5; //  1mA @ 5v =  5mW

// Alternate calibration by RAtkins via pre-PSU wattage measurments;
// these are all probably about 20%-25% too high due to PSU heat losses,
// but if you're measuring wattage on the PSU input side, this may
// be a better set of calibrations.  (WS2812B)
//  static const uint8_t gRed_mW   = 100;
//  static const uint8_t gGreen_mW =  48;
//  static const uint8_t gBlue_mW  = 100;
//  static const uint8_t gDark_mW  =  12;


#define POWER_LED 1
#define POWER_DEBUG_PRINT 0


// Power consumed by the MCU
static const uint8_t gMCU_mW  =  25 * 5; // 25mA @ 5v = 125 mW


static uint32_t gMaxPowerInMilliwatts = (uint32_t)(400) * (uint32_t)(5); // 400mA @ 5v default to avoid USB bricking
static uint8_t  gMaxPowerIndicatorLEDPinNumber = 0; // default = Arduino onboard LED pin.  set to zero to skip this.


uint32_t calculate_unscaled_power_mW( const CRGB* ledbuffer, uint16_t numLeds ) //25354
{
    uint32_t red32 = 0, green32 = 0, blue32 = 0;
    const CRGB* firstled = &(ledbuffer[0]);
    uint8_t* p = (uint8_t*)(firstled);
    
    uint16_t count = numLeds;
    
    // This loop might benefit from an AVR assembly version -MEK
    while( count) {
        red32   += *p++;
        green32 += *p++;
        blue32  += *p++;
        count--;
    }
    
    red32   *= gRed_mW;
    green32 *= gGreen_mW;
    blue32  *= gBlue_mW;
    
    red32   >>= 8;
    green32 >>= 8;
    blue32  >>= 8;
    
    uint32_t total = red32 + green32 + blue32 + (gDark_mW * numLeds);
    
    return total;
}



// sets brightness to
//  - no more than target_brightness
//  - no more than max_mW milliwatts
uint8_t calculate_max_brightness_for_power_mW( uint8_t target_brightness, uint32_t max_power_mW)
{
    uint32_t total_mW = gMCU_mW;
    
    CLEDController *pCur = CLEDController::head();
	while(pCur) {
        total_mW += calculate_unscaled_power_mW( pCur->leds(), pCur->size());
		pCur = pCur->next();
	}

#if POWER_DEBUG_PRINT == 1
    Serial.print("power demand at full brightness mW = ");
    Serial.println( total_mW);
#endif
    
    uint32_t requested_power_mW = ((uint32_t)total_mW * target_brightness) / 256;
#if POWER_DEBUG_PRINT == 1
    if( target_brightness != 255 ) {
        Serial.print("power demand at scaled brightness mW = ");
        Serial.println( requested_power_mW);
    }
    Serial.print("power limit mW = ");
    Serial.println( max_power_mW);
#endif
    
    if( requested_power_mW < max_power_mW) {
#if POWER_LED > 0
        if( gMaxPowerIndicatorLEDPinNumber ) {
            digitalWrite(gMaxPowerIndicatorLEDPinNumber, LOW);   // turn the LED off
        }
#endif
#if POWER_DEBUG_PRINT == 1
        Serial.print("demand is under the limit");
#endif
        return target_brightness;
    }
    
    uint8_t recommended_brightness = (uint32_t)((uint8_t)(target_brightness) * (uint32_t)(max_power_mW)) / ((uint32_t)(requested_power_mW));
#if POWER_DEBUG_PRINT == 1
    Serial.print("recommended brightness # = ");
    Serial.println( recommended_brightness);

    uint32_t resultant_power_mW = (total_mW * recommended_brightness) / 256;
    Serial.print("resultant power demand mW = ");
    Serial.println( resultant_power_mW);
    
    Serial.println();
#endif
    
#if POWER_LED > 0
    if( gMaxPowerIndicatorLEDPinNumber ) {
        digitalWrite( gMaxPowerIndicatorLEDPinNumber, HIGH);   // turn the LED on
    }
#endif
    
    return recommended_brightness;
}


void set_max_power_indicator_LED( uint8_t pinNumber)
{
    gMaxPowerIndicatorLEDPinNumber = pinNumber;
}

void set_max_power_in_volts_and_milliamps( uint8_t volts, uint32_t milliamps)
{
    gMaxPowerInMilliwatts = (uint32_t)((uint32_t)(volts) * milliamps);
}

void set_max_power_in_milliwatts( uint32_t powerInmW)
{
    gMaxPowerInMilliwatts = powerInmW;
}

void show_at_max_brightness_for_power()
{
    uint8_t targetBrightness = FastLED.getBrightness();
    uint8_t max = calculate_max_brightness_for_power_mW( targetBrightness, gMaxPowerInMilliwatts);
    
    FastLED.setBrightness( max );
    FastLED.show();
    FastLED.setBrightness( targetBrightness );
}

void delay_at_max_brightness_for_power( uint16_t ms)
{
    uint8_t targetBrightness = FastLED.getBrightness();
    uint8_t max = calculate_max_brightness_for_power_mW( targetBrightness, gMaxPowerInMilliwatts);
    
    FastLED.setBrightness( max );
    FastLED.delay( ms);
    FastLED.setBrightness( targetBrightness );
}