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diff --git a/libs-device/osccal.h b/libs-device/osccal.h
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+/* Name: osccal.h
+ * 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) or proprietary (CommercialLicense.txt)
+ * This Revision: $Id$
+ */
+
+/*
+General Description:
+This module contains a function which calibrates the AVR's internal RC
+oscillator so that the CPU runs at F_CPU (F_CPU is a macro which must be
+defined when the module is compiled, best passed in the compiler command
+line). The time reference is the USB frame clock of 1 kHz available
+immediately after a USB RESET condition. Timing is done by counting CPU
+cycles, so all interrupts must be disabled while the calibration runs. For
+low level timing measurements, usbMeasureFrameLength() is called. This
+function must be enabled in usbconfig.h by defining
+USB_CFG_HAVE_MEASURE_FRAME_LENGTH to 1.
+
+Algorithm used:
+calibrateOscillator() first does a binary search in the OSCCAL register for
+the best matching oscillator frequency. Then it does a next neighbor search
+to find the value with the lowest clock rate deviation. It is guaranteed to
+find the best match among neighboring values, but for version 5 oscillators
+(which have a discontinuous relationship between OSCCAL and frequency) a
+better match might be available in another OSCCAL region.
+
+Limitations:
+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!
+Precision depends on the OSCCAL vs. frequency dependency of the oscillator.
+Typical precision for an ATMega168 (derived from the OSCCAL vs. F_RC diagram
+in the data sheet) should be in the range of 0.4%. Only the 16.5 MHz version
+of AVR-USB (with built-in receiver PLL) can tolerate this deviation! All other
+frequency modules require at least 0.3% precision.
+*/
+
+#ifndef __OSCCAL_H_INCLUDED__
+#define __OSCCAL_H_INCLUDED__
+
+void    calibrateOscillator(void);
+/* This function calibrates the RC oscillator so that the CPU runs at F_CPU.
+ * It MUST be called immediately after the end of a USB RESET condition!
+ * Disable all interrupts during the call!
+ * It is recommended that you store the resulting value in EEPROM so that a
+ * good guess value is available after the next reset.
+ */
+
+
+#endif /* __OSCCAL_H_INCLUDED__ */