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ubb-vga.c (delay): try to compensate for APB jitter (experimental)
First, we extend all deadlines a litte to make sure we never have to wait negative time. Second, we get the timer value at the end of the wait and CPU-loop for the difference between the actual value and the ideal (extended) value.
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@ -244,11 +244,17 @@ static void cleanup(void)
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static void delay(uint16_t cycles)
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{
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static uint16_t next = 0;
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uint16_t t;
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next += cycles;
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TDHR(TIMER) = next;
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TFCR = 1 << (TIMER+16);
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while (!(TFR & (1 << (TIMER+16))));
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t = next+24-TCNT(TIMER);
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t >>= 1;
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while (t--)
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asm("");
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}
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