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Hi folks, does anybody know where I can find VHDL source for a quadrature decoder ? Also, I have a doubt about encoders' voltage levels: I think unipolar encoders are TTL compatible, so I can input their values directly into a FPGA, whereas I have no idea about how to interface bipolar encoders. Can anybody give me a hint ? Thanks, Guido following fits in a GAL 22V10. It generates an UP or DOWN
pulse from a quadrature signal.
There is one pulse on every edge of the encoder, so the
actual pulses per revolution are multiplied by 4.
I hope this wil help you. Any further questions, mail me
...
Luc Vercruysse
; pin assignments
PIN 2 CLK ; clock pin
PIN 3 A ; Channel A
PIN 4 B ; Channel B
PIN 20 S1
PIN 21 S2
PIN 23 S3 ;
PIN 24 S4 ;
PIN 17 UP
PIN 18 DOWN
PIN 19 PULSE
PIN 26 PHI0
PIN 27 PHI90
; Boolean equations for registers
EQUATIONS
PHI0 := A
PHI90 := B
/S1 := /PHI0
/S2 := /S1
/S3 := /PHI90
/S4 := /S3
DOWN = S1 * S2 * S3 * /S4 * PHI0 * PHI90
+ /S1 * /S2 * /S3 * S4 * /PHI0 * /PHI90
+ S1 * /S2 * /S3 * /S4 * PHI0 * /PHI90
+ /S1 * S2 * S3 * S4 * /PHI0 * PHI90
UP = /S1 * /S2 * S3 * /S4 * /PHI0 * PHI90
+ S1 * S2 * /S3 * S4 * PHI0 * /PHI90
+ S1 * /S2 * S3 * S4 * PHI0 * PHI90
+ /S1 * S2 * /S3 * /S4 * /PHI0 *
/PHI90
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