picorv32/scripts/icestorm/firmware.c

29 lines
583 B
C
Raw Normal View History

2015-07-19 22:09:19 +08:00
#include <stdint.h>
#define SHIFT_COUNTER_BITS 16
void output(uint8_t c)
{
*(volatile char*)0x10000000 = c;
}
void output_gray(uint8_t c)
{
unsigned int in_buf = c, out_buf = 0;
for (int i = 0; i < 8; i++) {
unsigned int bit = (in_buf & 1) ^ ((in_buf >> 1) & 1);
in_buf = in_buf >> 1;
out_buf = (out_buf << 1) | bit;
}
output(out_buf);
}
void main()
{
for (uint32_t counter = (2+4+32+64) << SHIFT_COUNTER_BITS;; counter++) {
asm volatile ("" : : "r"(counter));
if ((counter & ~(~0 << SHIFT_COUNTER_BITS)) == 0)
output_gray(counter >> SHIFT_COUNTER_BITS);
}
}