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Diffstat (limited to 'firmware/libs-device/osctune.h')
| -rw-r--r-- | firmware/libs-device/osctune.h | 88 |
1 files changed, 0 insertions, 88 deletions
diff --git a/firmware/libs-device/osctune.h b/firmware/libs-device/osctune.h deleted file mode 100644 index c751648..0000000 --- a/firmware/libs-device/osctune.h +++ /dev/null @@ -1,88 +0,0 @@ -/* Name: osctune.h - * Author: Christian Starkjohann - * Creation Date: 2008-10-18 - * 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: osctune.h 692 2008-11-07 15:07:40Z cs $ - */ - -/* -General Description: -This file is declared as C-header file although it is mostly documentation -how the RC oscillator can be kept in sync to the USB frame rate. The code -shown here must be added to usbconfig.h or this header file is included from -there. This code works only if D- is wired to the interrupt, not D+!!! - -This is an alternative to the osccal routine in osccal.c. It has the advantage -that the synchronization is done continuously and that it has more compact -code size. The disadvantages are slow synchronization (it may take a while -until the driver works), that messages immediately after the SOF pulse may be -lost (and need to be retried by the host) and that the interrupt is on D- -contrary to most examples. - -You may want to store a good calibration value in EEPROM for the next startup. -You know that the calibration value is good when the first USB message is -received. Do not store the value on every received message because the EEPROM -has a limited endurance. - -Notes: -(*) You must declare the global character variable "lastTimer0Value" in your -main code. - -(*) Timer 0 must be free running (not written by your code) and the prescaling -must be consistent with the TIMER0_PRESCALING define. - -(*) Good values for Timer 0 prescaling depend on how precise the clock must -be tuned and how far away from the default clock rate the target clock is. -For precise tuning, choose a low prescaler factor, for a broad range of tuning -choose a high one. A prescaler factor of 64 is good for the entire OSCCAL -range and allows a precision of better than +/-1%. A prescaler factor of 8 -allows tuning to slightly more than +/-6% of the default frequency and is -more precise than one step of OSCCAL. It is therefore not suitable to tune an -8 MHz oscillator to 12.5 MHz. - -Thanks to Henrik Haftmann for the idea to this routine! -*/ - -#define TIMER0_PRESCALING 64 /* must match the configuration for TIMER0 in main */ -#define TOLERATED_DEVIATION_PPT 5 /* max clock deviation before we tune in 1/10 % */ -/* derived constants: */ -#define EXPECTED_TIMER0_INCREMENT ((F_CPU / (1000 * TIMER0_PRESCALING)) & 0xff) -#define TOLERATED_DEVIATION (TOLERATED_DEVIATION_PPT * F_CPU / (1000000 * TIMER0_PRESCALING)) - -#ifdef __ASSEMBLER__ -macro tuneOsccal - push YH ;[0] - in YL, TCNT0 ;[2] - lds YH, lastTimer0Value ;[3] - sts lastTimer0Value, YL ;[5] - sub YL, YH ;[7] time passed since last frame - subi YL, EXPECTED_TIMER0_INCREMENT ;[8] -#if OSCCAL > 0x3f /* outside I/O addressable range */ - lds YH, OSCCAL ;[6] -#else - in YH, OSCCAL ;[6] assembler modle uses __SFR_OFFSET == 0 -#endif - cpi YL, TOLERATED_DEVIATION + 1 ;[10] - brmi notTooHigh ;[11] - subi YH, 1 ;[12] clock rate was too high -; brcs tuningOverflow ; optionally check for overflow - rjmp osctuneDone ;[13] -notTooHigh: - cpi YL, -TOLERATED_DEVIATION ;[13] - brpl osctuneDone ;[14] not too low - inc YH ;[15] clock rate was too low -; breq tuningOverflow ; optionally check for overflow -osctuneDone: -#if OSCCAL > 0x3f /* outside I/O addressable range */ - sts OSCCAL, YH ;[12-13] store tuned value -#else - out OSCCAL, YH ;[12-13] store tuned value -#endif -tuningOverflow: - pop YH ;[17] - endm ;[19] max number of cycles -#endif - -#define USB_SOF_HOOK tuneOsccal |