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Fix PIO count (#211)

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Works fine currently for low frequency, breaks down at higher frequency e.g. 1MHz

Chased down with a scope to the 3 extra cycles needed for wait+1; mov; jmp
so account for these in demo program
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Graeme Winter 2022-05-16 21:17:42 +01:00 committed by GitHub
parent 4d1d533122
commit 72e41ad66f
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1 changed files with 4 additions and 1 deletions
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5
pio/pio_blink/blink.c
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@ -31,5 +31,8 @@ void blink_pin_forever(PIO pio, uint sm, uint offset, uint pin, uint freq) {
pio_sm_set_enabled(pio, sm, true); pio_sm_set_enabled(pio, sm, true);
printf("Blinking pin %d at %d Hz\n", pin, freq); printf("Blinking pin %d at %d Hz\n", pin, freq);
pio->txf[sm] = clock_get_hz(clk_sys) / (2 * freq);
// PIO counter program takes 3 more cycles in total than we pass as
// input (wait for n + 1; mov; jmp)
pio->txf[sm] = (clock_get_hz(clk_sys) / (2 * freq)) - 3;
} }