mirror of https://github.com/YosysHQ/picorv32.git
58 lines
1.1 KiB
C
58 lines
1.1 KiB
C
#include <stdint.h>
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// use SHIFT_COUNTER_BITS=4 for simulation
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#define SHIFT_COUNTER_BITS 18
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void output(uint8_t c)
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{
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*(volatile char*)0x10000000 = c;
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}
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uint8_t gray_encode_simple(uint8_t c)
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{
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return c ^ (c >> 1);
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}
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uint8_t gray_encode_bitwise(uint8_t c)
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{
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unsigned int in_buf = c, out_buf = 0, bit = 1;
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for (int i = 0; i < 8; i++) {
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if ((in_buf & 1) ^ ((in_buf >> 1) & 1))
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out_buf |= bit;
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in_buf = in_buf >> 1;
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bit = bit << 1;
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}
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return out_buf;
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}
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uint8_t gray_decode(uint8_t c)
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{
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uint8_t t = c >> 1;
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while (t) {
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c = c ^ t;
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t = t >> 1;
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}
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return c;
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}
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void gray(uint8_t c)
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{
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uint8_t gray_simple = gray_encode_simple(c);
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uint8_t gray_bitwise = gray_encode_bitwise(c);
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uint8_t gray_decoded = gray_decode(gray_simple);
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if (gray_simple != gray_bitwise || gray_decoded != c)
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while (1) asm volatile ("sbreak");
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output(gray_simple);
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}
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void main()
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{
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for (uint32_t counter = (2+4+32+64) << SHIFT_COUNTER_BITS;; counter++) {
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asm volatile ("" : : "r"(counter));
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if ((counter & ~(~0 << SHIFT_COUNTER_BITS)) == 0)
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gray(counter >> SHIFT_COUNTER_BITS);
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}
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}
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