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Diffstat (limited to 'firmware/libs-device/osccal.c')
| -rw-r--r-- | firmware/libs-device/osccal.c | 183 |
1 files changed, 0 insertions, 183 deletions
diff --git a/firmware/libs-device/osccal.c b/firmware/libs-device/osccal.c deleted file mode 100644 index 8debe49..0000000 --- a/firmware/libs-device/osccal.c +++ /dev/null @@ -1,183 +0,0 @@ -/* Name: osccal.c - * Author: Christian Starkjohann - * Creation Date: 2008-04-10 - * Tabsize: 4 - * Copyright: (c) 2008 by OBJECTIVE DEVELOPMENT Software GmbH - * License: GNU GPL v2 (see License.txt), GNU GPL v3 or proprietary (CommercialLicense.txt) - * This Revision: $Id: osccal.c 762 2009-08-12 17:10:30Z cs $ - */ - -#include <avr/io.h> -#include <avr/interrupt.h> -#ifndef uchar -#define uchar unsigned char -#endif - -int usbMeasureFrameLengthDecreasing(int); - -/* ------------------------------------------------------------------------- */ -/* ------------------------ Oscillator Calibration ------------------------- */ -/* ------------------------------------------------------------------------- */ - -/* Calibrate the RC oscillator. Our timing reference is the Start Of Frame - * signal (a single SE0 bit) repeating every millisecond immediately after - * a USB RESET. - * - * - * Optimized version by cpldcpu@gmail.com, Nov 3rd 2013. - * - * Benefits: - * - Codesize reduced by 54 bytes. - * - Improved robustness due to removing timeout from frame length measurement and - * inserted NOP after OSCCAL writes. - * - * Changes: - * - The new routine performs a combined binary and neighborhood search - * in a single loop. - * Note that the neighborhood search is necessary due to the quasi-monotonic - * nature of OSCCAL. (See Atmel application note AVR054). - * - Inserted NOP after writes to OSCCAL to avoid CPU errors during oscillator - * stabilization. - * - Implemented new routine to measure frame time "usbMeasureFrameLengthDecreasing". - * This routine takes the target time as a parameter and returns the deviation. - * - usbMeasureFrameLengthDecreasing measures in multiples of 5 cycles and is thus - * slighly more accurate. - * - usbMeasureFrameLengthDecreasing does not support time out anymore. The original - * implementation returned zero in case of time out, which would have caused the old - * calibrateOscillator() implementation to increase OSSCAL to 255, effictively - * overclocking and most likely crashing the CPU. The new implementation will enter - * an infinite loop when no USB activity is encountered. The user program should - * use the watchdog to escape from situations like this. - * - * This routine will work both on controllers with and without split OSCCAL range. - * The first trial value is 128 which is the lowest value of the upper OSCCAL range - * on Attiny85 and will effectively limit the search to the upper range, unless the - * RC oscillator frequency is unusually high. Under normal operation, the highest - * tested frequency setting is 192. This corresponds to ~20 Mhz core frequency and - * is still within spec for a 5V device. - */ - -void calibrateOscillator(void) -{ - uchar step, trialValue, optimumValue; - int x, targetValue; - uchar optimumDev; - uchar i,xl; - - targetValue = (unsigned)((double)F_CPU * 999e-6 / 5.0 + 0.5); /* Time is measured in multiples of 5 cycles. Target is 0.999µs */ - optimumDev = 0xff; - // optimumValue = OSCCAL; - step=64; - trialValue = 128; - - cli(); // disable interrupts - - /* - Performs seven iterations of a binary search (stepwidth decreasing9 - with three additional steps of a neighborhood search (step=1, trialvalue will oscillate around target value to find optimum) - */ - - for(i=0; i<10; i++){ - OSCCAL = trialValue; - asm volatile(" NOP"); - - x = usbMeasureFrameLengthDecreasing(targetValue); - - if(x < 0) /* frequency too high */ - { - trialValue -= step; - xl=(uchar)-x; - } - else /* frequency too low */ - { - trialValue += step; - xl=(uchar)x; - } - - /* - Halve stepwidth to perform binary search. Logical oring with 1 to ensure step is never equal to zero. - This results in a neighborhood search with stepwidth 1 after binary search is finished. - Once the neighbourhood search stage is reached, x will be smaller than +-255, hence more code can be - saved by only working with the lower 8 bits. - */ - - step >>= 1; - - if (step==0) - { - step=1; - if(xl <= optimumDev){ - optimumDev = xl; - optimumValue = OSCCAL; - } - } - - } - - OSCCAL = optimumValue; - asm volatile(" NOP"); - - sei(); // enable interrupts -} - -void calibrateOscillator_old(void) -{ - uchar step, trialValue, optimumValue; - int x, optimumDev, targetValue; - uchar i; - - targetValue = (unsigned)((double)F_CPU * 999e-6 / 5.0 + 0.5); /* Time is measured in multiples of 5 cycles. Target is 0.999µs */ - optimumDev = 0x7f00; // set to high positive value - optimumValue = OSCCAL; - step=64; - trialValue = 128; - - /* - Performs seven iterations of a binary search (stepwidth decreasing9 - with three additional steps of a neighborhood search (step=1, trialvalue will oscillate around target value to find optimum) - */ - - for(i=0; i<10; i++){ - OSCCAL = trialValue; - asm volatile(" NOP"); - - x = usbMeasureFrameLengthDecreasing(targetValue); - - if(x < 0) /* frequency too high */ - { - trialValue -= step; - x = -x; - } - else /* frequency too low */ - { - trialValue += step; - } - - /* - Halve stepwidth to perform binary search. Logical oring with 1 to ensure step is never equal to zero. - This results in a neighborhood search with stepwidth 1 after binary search is finished. - */ - - step >>= 1; - step |=1; - - if(x < optimumDev){ - optimumDev = x; - optimumValue = OSCCAL; - } - } - - OSCCAL = optimumValue; - asm volatile(" NOP"); -} - -/* -Note: This calibration algorithm may try OSCCAL values of up to 192 even if -the optimum value is far below 192. It may therefore exceed the allowed clock -frequency of the CPU in low voltage designs! -You may replace this search algorithm with any other algorithm you like if -you have additional constraints such as a maximum CPU clock. -For version 5.x RC oscillators (those with a split range of 2x128 steps, e.g. -ATTiny25, ATTiny45, ATTiny85), it may be useful to search for the optimum in -both regions. -*/ |