--- /dev/null
+/* Name: osccalASM.S
+ * Author: cpldcpu@gmail.com
+ * Creation Date: 2013-11-3
+ * Tabsize: 4
+ * License: GNU GPL v2 (see License.txt), GNU GPL v3 or proprietary (CommercialLicense.txt)
+ */
+
+/* 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.
+ *
+ *
+ * Benefits:
+ * - Codesize reduced by 90 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.
+ */
+
+
+#define __SFR_OFFSET 0 /* used by avr-libc's register definitions */
+#include "./usbdrv/usbdrv.h" /* for common defs */
+
+#ifdef __IAR_SYSTEMS_ASM__
+/* Register assignments for usbMeasureFrameLengthDecreasing on IAR cc */
+/* Calling conventions on IAR:
+ * First parameter passed in r16/r17, second in r18/r19 and so on.
+ * Callee must preserve r4-r15, r24-r29 (r28/r29 is frame pointer)
+ * Result is passed in r16/r17
+ * In case of the "tiny" memory model, pointers are only 8 bit with no
+ * padding. We therefore pass argument 1 as "16 bit unsigned".
+ */
+
+//Untested
+
+# define i r20
+# define opV r19
+# define opD r18
+# define try r21
+# define stp r22
+
+# define cnt16L r30
+# define cnt16H r31
+
+
+#else /* __IAR_SYSTEMS_ASM__ */
+/* Register assignments for usbMeasureFrameLength on gcc */
+/* Calling conventions on gcc:
+ * First parameter passed in r24/r25, second in r22/23 and so on.
+ * Callee must preserve r1-r17, r28/r29
+ * Result is passed in r24/r25
+ */
+
+# define i r20
+# define opV r19
+# define opD r18
+# define try r27
+# define stp r26
+# define cnt16L r24
+# define cnt16H r25
+#endif
+# define cnt16 cnt16L
+
+; extern void calibrateOscillatorASM(void);
+
+.global calibrateOscillatorASM
+calibrateOscillatorASM:
+
+ cli
+ ldi opD, 255
+
+ ldi try, 128 ; calibration start value
+ ldi stp, 64 ; initial step width
+ ldi i, 10 ; 10 iterations
+
+usbCOloop:
+
+ out OSCCAL, try
+ nop
+
+ ; Delay values = F_CPU * 999e-6 / 5 + 0.5
+
+#if (F_CPU == 16500000)
+ ldi cnt16L, lo8(3297)
+ ldi cnt16H, hi8(3297)
+#elif (F_CPU == 12800000)
+ ldi cnt16L, lo8(2557)
+ ldi cnt16H, hi8(2557)
+#else
+ #error "calibrateOscillatorASM: no delayvalues defined for this F_CPU setting"
+#endif
+
+usbCOWaitStrobe: ; first wait for D- == 0 (idle strobe)
+ sbic USBIN, USBMINUS ;
+ rjmp usbCOWaitStrobe ;
+usbCOWaitIdle: ; then wait until idle again
+ sbis USBIN, USBMINUS ;1 wait for D- == 1
+ rjmp usbCOWaitIdle ;2
+usbCOWaitLoop:
+ sbiw cnt16,1 ;[0] [5]
+ sbic USBIN, USBMINUS ;[2]
+ rjmp usbCOWaitLoop ;[3]
+
+ sbrs cnt16H, 7 ;delay overflow?
+ rjmp usbCOclocktoolow
+ sub try, stp
+ neg cnt16L
+ rjmp usbCOclocktoohigh
+usbCOclocktoolow:
+ add try, stp
+usbCOclocktoohigh:
+ lsr stp
+ brne usbCOnoneighborhoodsearch
+ cp opD, cnt16L
+ brcs usbCOnoimprovement
+ in opV, OSCCAL
+ mov opD, cnt16L
+usbCOnoimprovement:
+ ldi stp, 1
+usbCOnoneighborhoodsearch:
+ subi i, 1
+ brne usbCOloop
+
+ out OSCCAL, opV
+ nop
+ sei
+ ret
+
+#undef i
+#undef opV
+#undef opD
+#undef try
+#undef stp
+#undef cnt16
+#undef cnt16L
+#undef cnt16H
+
+/* ------------------------------------------------------------------------- */
+/* ------ Original C Implementation of improved calibrateOscillator -------- */
+/* ---------------------- for Reference only ----------------------------- */
+/* ------------------------------------------------------------------------- */
+
+#if 0
+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. At step=1 the mode changes to neighbourhood search.
+ 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) // Enter neighborhood search mode
+ {
+ step=1;
+ if(xl <= optimumDev){
+ optimumDev = xl;
+ optimumValue = OSCCAL;
+ }
+ }
+ }
+
+ OSCCAL = optimumValue;
+ asm volatile(" NOP");
+
+ sei(); // enable interrupts
+}
+#endif
projects / energenie-attiny.git / blobdiff