TSL237 light to frequency detector
ratronic
Posts: 1,451
I decided to check out Parallax's light sensor and wrote a simple program to display the output frequency to the serial terminal. Sitting indoors @ ~5:00 with the TV's on lights off I get around 3 - 4 kHz.
With the room light turned on I get ~ 53 khz. Since this is so sensitive I am averaging 512 samples to smooth it out. I seem to remember reading another thread were I think people were saying
that they usually don't reset the phsa in their program. I'm doing it here and it seems to work ok.
With the room light turned on I get ~ 53 khz. Since this is so sensitive I am averaging 512 samples to smooth it out. I seem to remember reading another thread were I think people were saying
that they usually don't reset the phsa in their program. I'm doing it here and it seems to work ok.
Con 'capture frequency output from tsl237 to serial terminal (run tsl237 from 3.3v)
'assembly routine sets counter to capture clk cycles while APIN is low and return full clock freq averaged 512 times
_CLKMODE = XTAL1 + PLL16X
_XINFREQ = 5_000_000
APIN = 2 'propeller port connected to tsl237 output pin
Var
long freq
Obj
pst : "parallax serial terminal"
Pub Main
pst.start(9600)
cognew(@entry, @freq)
repeat
pst.char(1)
pst.str(string("Frequency = "))
pst.dec(clkfreq / freq)
pst.chars(32, 10)
Dat
org 0
Entry
mov t1, cntr 'set t1 loop counter
movs ctra, #APIN 'set counter Apin
movi ctra, #101_000 'set counter to accumulate when counter Apin is low
waitpne pin, pin 'wait for counter Apin to be low
waitpeq pin, pin 'wait for counter Apin to be high
mov frqa, #1 'start accumulating in phsa when counter Apin/condition is met
:loop
waitpne pin, pin 'wait for counter Apin to go low
waitpeq pin, pin 'wait for counter Apin to go high
add t2, phsa 'add # clk cycles Apin was low in t2
mov phsa, #0 'reset accumulator to 0
djnz t1, #:loop 'repeat this loop t1(cntr) times
sar t2, #9 'divide t2 by 512 to get average of A pin low lengths
shl t2, #1 'multiply t2 by 2 to represent a full clock length (high & low)
wrlong t2, par 'write t2 to hub variable freq
mov t1, cntr 'set t1 loop counter
jmp #:loop 'start loop again
pin long 1 << APIN 'pinmask for counter Apin
cntr long 512 '# of times to average output
t1 res 1 'temp var used for averaging loop counter
t2 res 1 'temp var used for processing and writing to hub clk length freq
zip
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