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https://github.com/digistump/DigistumpArduino.git
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change folder names, remove duplicate DigiJoystick folder
This commit is contained in:
Erik Tylek Kettenburg
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This is the Readme file for the libs-device directory. This directory contains
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code snippets which may be useful for USB device firmware.
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WHAT IS INCLUDED IN THIS DIRECTORY?
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===================================
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osccal.c and osccal.h
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This module contains a function which calibrates the AVR's built-in RC
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oscillator based on the USB frame clock. See osccal.h for a documentation
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of the API.
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osctune.h
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This header file contains a code snippet for usbconfig.h. With this code,
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you can keep the AVR's internal RC oscillator in sync with the USB frame
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clock. This is a continuous synchronization, not a single calibration at
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USB reset as with osccal.c above. Please note that this code works only
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if D- is wired to the interrupt, not D+.
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----------------------------------------------------------------------------
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(c) 2008 by OBJECTIVE DEVELOPMENT Software GmbH.
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http://www.obdev.at/
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/* Name: osccal.c
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* Author: Christian Starkjohann
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* Creation Date: 2008-04-10
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* Tabsize: 4
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* Copyright: (c) 2008 by OBJECTIVE DEVELOPMENT Software GmbH
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* License: GNU GPL v2 (see License.txt), GNU GPL v3 or proprietary (CommercialLicense.txt)
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* This Revision: $Id: osccal.c 762 2009-08-12 17:10:30Z cs $
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*/
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#include <avr/io.h>
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#ifndef uchar
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#define uchar unsigned char
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#endif
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/* ------------------------------------------------------------------------- */
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/* ------------------------ Oscillator Calibration ------------------------- */
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/* ------------------------------------------------------------------------- */
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/* Calibrate the RC oscillator. Our timing reference is the Start Of Frame
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* signal (a single SE0 bit) repeating every millisecond immediately after
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* a USB RESET. We first do a binary search for the OSCCAL value and then
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* optimize this value with a neighboorhod search.
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*/
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void calibrateOscillator(void)
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{
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uchar step = 128;
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uchar trialValue = 0, optimumValue;
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int x, optimumDev, targetValue = (unsigned)(1499 * (double)F_CPU / 10.5e6 + 0.5);
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/* do a binary search: */
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do{
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OSCCAL = trialValue + step;
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x = usbMeasureFrameLength(); /* proportional to current real frequency */
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if(x < targetValue) /* frequency still too low */
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trialValue += step;
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step >>= 1;
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}while(step > 0);
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/* We have a precision of +/- 1 for optimum OSCCAL here */
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/* now do a neighborhood search for optimum value */
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optimumValue = trialValue;
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optimumDev = x; /* this is certainly far away from optimum */
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for(OSCCAL = trialValue - 1; OSCCAL <= trialValue + 1; OSCCAL++){
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x = usbMeasureFrameLength() - targetValue;
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if(x < 0)
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x = -x;
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if(x < optimumDev){
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optimumDev = x;
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optimumValue = OSCCAL;
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}
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}
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OSCCAL = optimumValue;
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}
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/*
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Note: This calibration algorithm may try OSCCAL values of up to 192 even if
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the optimum value is far below 192. It may therefore exceed the allowed clock
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frequency of the CPU in low voltage designs!
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You may replace this search algorithm with any other algorithm you like if
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you have additional constraints such as a maximum CPU clock.
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For version 5.x RC oscillators (those with a split range of 2x128 steps, e.g.
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ATTiny25, ATTiny45, ATTiny85), it may be useful to search for the optimum in
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both regions.
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*/
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GAS LISTING C:\Users\Erik\AppData\Local\Temp/ccabieCZ.s page 1
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1 .file "osccal.c"
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2 __SREG__ = 0x3f
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3 __SP_H__ = 0x3e
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4 __SP_L__ = 0x3d
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5 __CCP__ = 0x34
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6 __tmp_reg__ = 0
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7 __zero_reg__ = 1
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8 .text
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9 .global calibrateOscillator
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10 .type calibrateOscillator, @function
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11 calibrateOscillator:
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12 0000 FF92 push r15
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13 0002 0F93 push r16
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14 0004 1F93 push r17
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15 0006 CF93 push r28
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16 0008 DF93 push r29
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17 /* prologue: function */
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18 /* frame size = 0 */
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19 000a 80E8 ldi r24,lo8(-128)
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20 000c F82E mov r15,r24
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21 000e 00E0 ldi r16,lo8(0)
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22 0010 C0E0 ldi r28,lo8(0)
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23 0012 D0E0 ldi r29,hi8(0)
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24 .L4:
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25 0014 102F mov r17,r16
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26 0016 1F0D add r17,r15
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27 0018 11BF out 81-32,r17
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28 001a 00D0 rcall usbMeasureFrameLength
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29 001c 29E0 ldi r18,hi8(2356)
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30 001e 8433 cpi r24,lo8(2356)
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31 0020 9207 cpc r25,r18
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32 0022 04F0 brlt .L2
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33 0024 102F mov r17,r16
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34 .L2:
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35 0026 F694 lsr r15
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36 0028 2196 adiw r28,1
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37 002a C830 cpi r28,8
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38 002c D105 cpc r29,__zero_reg__
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39 002e 01F0 breq .L3
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40 0030 012F mov r16,r17
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41 0032 00C0 rjmp .L4
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42 .L3:
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43 0034 1150 subi r17,lo8(-(-1))
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44 0036 11BF out 81-32,r17
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45 0038 1F5F subi r17,lo8(-(1))
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46 003a 012F mov r16,r17
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47 003c EC01 movw r28,r24
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48 003e 00C0 rjmp .L5
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49 .L8:
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50 0040 00D0 rcall usbMeasureFrameLength
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51 0042 8453 subi r24,lo8(-(-2356))
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52 0044 9940 sbci r25,hi8(-(-2356))
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53 0046 97FF sbrs r25,7
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54 0048 00C0 rjmp .L6
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55 004a 9095 com r25
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56 004c 8195 neg r24
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57 004e 9F4F sbci r25,lo8(-1)
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GAS LISTING C:\Users\Erik\AppData\Local\Temp/ccabieCZ.s page 2
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58 .L6:
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59 0050 8C17 cp r24,r28
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60 0052 9D07 cpc r25,r29
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61 0054 04F4 brge .L7
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62 0056 01B7 in r16,81-32
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63 0058 EC01 movw r28,r24
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64 .L7:
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65 005a 81B7 in r24,81-32
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66 005c 8F5F subi r24,lo8(-(1))
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67 005e 81BF out 81-32,r24
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68 .L5:
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69 0060 21B7 in r18,81-32
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70 0062 30E0 ldi r19,lo8(0)
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71 0064 812F mov r24,r17
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72 0066 90E0 ldi r25,lo8(0)
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73 0068 0196 adiw r24,1
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74 006a 8217 cp r24,r18
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75 006c 9307 cpc r25,r19
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76 006e 04F4 brge .L8
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77 0070 01BF out 81-32,r16
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78 /* epilogue start */
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79 0072 DF91 pop r29
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80 0074 CF91 pop r28
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81 0076 1F91 pop r17
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82 0078 0F91 pop r16
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83 007a FF90 pop r15
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84 007c 0895 ret
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85 .size calibrateOscillator, .-calibrateOscillator
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GAS LISTING C:\Users\Erik\AppData\Local\Temp/ccabieCZ.s page 3
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DEFINED SYMBOLS
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*ABS*:00000000 osccal.c
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C:\Users\Erik\AppData\Local\Temp/ccabieCZ.s:2 *ABS*:0000003f __SREG__
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C:\Users\Erik\AppData\Local\Temp/ccabieCZ.s:3 *ABS*:0000003e __SP_H__
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C:\Users\Erik\AppData\Local\Temp/ccabieCZ.s:4 *ABS*:0000003d __SP_L__
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C:\Users\Erik\AppData\Local\Temp/ccabieCZ.s:5 *ABS*:00000034 __CCP__
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C:\Users\Erik\AppData\Local\Temp/ccabieCZ.s:6 *ABS*:00000000 __tmp_reg__
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C:\Users\Erik\AppData\Local\Temp/ccabieCZ.s:7 *ABS*:00000001 __zero_reg__
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C:\Users\Erik\AppData\Local\Temp/ccabieCZ.s:11 .text:00000000 calibrateOscillator
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UNDEFINED SYMBOLS
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usbMeasureFrameLength
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/* Name: osccal.h
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* Author: Christian Starkjohann
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* Creation Date: 2008-04-10
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* Tabsize: 4
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* Copyright: (c) 2008 by OBJECTIVE DEVELOPMENT Software GmbH
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* License: GNU GPL v2 (see License.txt), GNU GPL v3 or proprietary (CommercialLicense.txt)
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* This Revision: $Id: osccal.h 762 2009-08-12 17:10:30Z cs $
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*/
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/*
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General Description:
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This module contains a function which calibrates the AVR's internal RC
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oscillator so that the CPU runs at F_CPU (F_CPU is a macro which must be
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defined when the module is compiled, best passed in the compiler command
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line). The time reference is the USB frame clock of 1 kHz available
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immediately after a USB RESET condition. Timing is done by counting CPU
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cycles, so all interrupts must be disabled while the calibration runs. For
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low level timing measurements, usbMeasureFrameLength() is called. This
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function must be enabled in usbconfig.h by defining
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USB_CFG_HAVE_MEASURE_FRAME_LENGTH to 1. It is recommended to call
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calibrateOscillator() from the reset hook in usbconfig.h:
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*/
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#ifndef __ASSEMBLER__
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#include <avr/interrupt.h> // for sei()
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extern void calibrateOscillator(void);
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#endif
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#define USB_RESET_HOOK(resetStarts) if(!resetStarts){cli(); calibrateOscillator(); sei();}
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/*
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This routine is an alternative to the continuous synchronization described
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in osctune.h.
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Algorithm used:
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calibrateOscillator() first does a binary search in the OSCCAL register for
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the best matching oscillator frequency. Then it does a next neighbor search
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to find the value with the lowest clock rate deviation. It is guaranteed to
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find the best match among neighboring values, but for version 5 oscillators
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(which have a discontinuous relationship between OSCCAL and frequency) a
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better match might be available in another OSCCAL region.
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Limitations:
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This calibration algorithm may try OSCCAL values of up to 192 even if the
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optimum value is far below 192. It may therefore exceed the allowed clock
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frequency of the CPU in low voltage designs!
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Precision depends on the OSCCAL vs. frequency dependency of the oscillator.
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Typical precision for an ATMega168 (derived from the OSCCAL vs. F_RC diagram
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in the data sheet) should be in the range of 0.4%. Only the 12.8 MHz and
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16.5 MHz versions of V-USB (with built-in receiver PLL) can tolerate this
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deviation! All other frequency modules require at least 0.2% precision.
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*/
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#ifndef __OSCCAL_H_INCLUDED__
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#define __OSCCAL_H_INCLUDED__
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//void calibrateOscillator(void);
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/* This function calibrates the RC oscillator so that the CPU runs at F_CPU.
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* It MUST be called immediately after the end of a USB RESET condition!
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* Disable all interrupts during the call!
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* It is recommended that you store the resulting value in EEPROM so that a
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* good guess value is available after the next reset.
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*/
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#endif /* __OSCCAL_H_INCLUDED__ */
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Binary file not shown.
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/* Name: osctune.h
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* Author: Christian Starkjohann
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* Creation Date: 2008-10-18
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* Tabsize: 4
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* Copyright: (c) 2008 by OBJECTIVE DEVELOPMENT Software GmbH
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* License: GNU GPL v2 (see License.txt), GNU GPL v3 or proprietary (CommercialLicense.txt)
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* This Revision: $Id: osctune.h 692 2008-11-07 15:07:40Z cs $
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*/
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/*
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General Description:
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This file is declared as C-header file although it is mostly documentation
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how the RC oscillator can be kept in sync to the USB frame rate. The code
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shown here must be added to usbconfig.h or this header file is included from
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there. This code works only if D- is wired to the interrupt, not D+!!!
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This is an alternative to the osccal routine in osccal.c. It has the advantage
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that the synchronization is done continuously and that it has more compact
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code size. The disadvantages are slow synchronization (it may take a while
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until the driver works), that messages immediately after the SOF pulse may be
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lost (and need to be retried by the host) and that the interrupt is on D-
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contrary to most examples.
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You may want to store a good calibration value in EEPROM for the next startup.
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You know that the calibration value is good when the first USB message is
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received. Do not store the value on every received message because the EEPROM
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has a limited endurance.
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Notes:
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(*) You must declare the global character variable "lastTimer0Value" in your
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main code.
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(*) Timer 0 must be free running (not written by your code) and the prescaling
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must be consistent with the TIMER0_PRESCALING define.
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(*) Good values for Timer 0 prescaling depend on how precise the clock must
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be tuned and how far away from the default clock rate the target clock is.
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For precise tuning, choose a low prescaler factor, for a broad range of tuning
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choose a high one. A prescaler factor of 64 is good for the entire OSCCAL
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range and allows a precision of better than +/-1%. A prescaler factor of 8
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allows tuning to slightly more than +/-6% of the default frequency and is
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more precise than one step of OSCCAL. It is therefore not suitable to tune an
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8 MHz oscillator to 12.5 MHz.
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Thanks to Henrik Haftmann for the idea to this routine!
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*/
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#define TIMER0_PRESCALING 64 /* must match the configuration for TIMER0 in main */
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#define TOLERATED_DEVIATION_PPT 5 /* max clock deviation before we tune in 1/10 % */
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/* derived constants: */
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#define EXPECTED_TIMER0_INCREMENT ((F_CPU / (1000 * TIMER0_PRESCALING)) & 0xff)
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#define TOLERATED_DEVIATION (TOLERATED_DEVIATION_PPT * F_CPU / (1000000 * TIMER0_PRESCALING))
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#ifdef __ASSEMBLER__
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macro tuneOsccal
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push YH ;[0]
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in YL, TCNT0 ;[2]
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lds YH, lastTimer0Value ;[3]
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sts lastTimer0Value, YL ;[5]
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sub YL, YH ;[7] time passed since last frame
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subi YL, EXPECTED_TIMER0_INCREMENT ;[8]
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#if OSCCAL > 0x3f /* outside I/O addressable range */
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lds YH, OSCCAL ;[6]
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#else
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in YH, OSCCAL ;[6] assembler modle uses __SFR_OFFSET == 0
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#endif
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cpi YL, TOLERATED_DEVIATION + 1 ;[10]
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brmi notTooHigh ;[11]
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subi YH, 1 ;[12] clock rate was too high
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; brcs tuningOverflow ; optionally check for overflow
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rjmp osctuneDone ;[13]
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notTooHigh:
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cpi YL, -TOLERATED_DEVIATION ;[13]
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brpl osctuneDone ;[14] not too low
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inc YH ;[15] clock rate was too low
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; breq tuningOverflow ; optionally check for overflow
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osctuneDone:
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#if OSCCAL > 0x3f /* outside I/O addressable range */
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sts OSCCAL, YH ;[12-13] store tuned value
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#else
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out OSCCAL, YH ;[12-13] store tuned value
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#endif
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tuningOverflow:
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pop YH ;[17]
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endm ;[19] max number of cycles
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#endif
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#define USB_SOF_HOOK tuneOsccal
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Block a user