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match the latest core code #46

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Merged
merged 3 commits into from
May 6, 2022
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match the latest core code #46

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3a9a028
match the latest core code
jepler May 6, 2022
387abbb
Add neopixel background example
jepler May 6, 2022
079fe9e
Fix comments based on review notes
jepler May 6, 2022
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21 changes: 12 additions & 9 deletions examples/pioasm_neopixel.py
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Original file line number Diff line number Diff line change
Expand Up @@ -8,19 +8,22 @@
import microcontroller
import adafruit_pioasm

# NeoPixels are 800khz bit streams. Zeroes are 1/3 duty cycle (~416ns) and ones
# are 2/3 duty cycle (~833ns).
# NeoPixels are 800khz bit streams. We are choosing zeros as <312ns hi, 936 lo> and ones
# and ones as <700 ns hi, 556 ns lo>.
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Looks like a repetition of "and ones"

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@dhalbert will want to fix this in the core, I think I faithfully copy-pasted it 😀

# cycle. The first two instructions always run while only one of the two final
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I think "cycle" may be a carryover from the old text?

# instructions run per bit. We start with the low period because it can be
# longer while waiting for more data.
program = """
.program ws2812
.side_set 1
.wrap_target
bitloop:
out x 1 side 0 [1]; Side-set still takes place when instruction stalls
jmp !x do_zero side 1 [1]; Branch on the bit we shifted out. Positive pulse
do_one:
jmp bitloop side 1 [1]; Continue driving high, for a long pulse
do_zero:
nop side 0 [1]; Or drive low, for a short pulse
out x 1 side 0 [6]; Drive low. Side-set still takes place before instruction stalls.
jmp !x do_zero side 1 [3]; Branch on the bit we shifted out previous delay. Drive high.
do_one:
jmp bitloop side 1 [4]; Continue driving high, for a one (long pulse)
do_zero:
nop side 0 [4]; Or drive low, for a zero (short pulse)
.wrap
"""

Expand All @@ -35,7 +38,7 @@

sm = rp2pio.StateMachine(
assembled,
frequency=800000 * 6, # 800khz * 6 clocks per bit
frequency=12_800_000, # to get appropriate sub-bit times in PIO program
first_sideset_pin=NEOPIXEL,
auto_pull=True,
out_shift_right=False,
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