[Q]HOW to measure the square wave length ??

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eos33

Joined: 24 Mar 2004
Posts: 2

06 Nov 2004 3:26 [Q]HOW to measure the square wave length ??

Dear all,
I 'd like to make a square wave measurement circuit to record the serial signal from
infrared remote control or radio control encoder.

Refer to the figure I attached~~

T1 : Signal A High Time
T2 : Signal A Low Time
T3 : Signal A High Time

I have a standard 8951 single chip and a Lattice 4032 CPLD.
Could you please give me some suggestions or ideas for implement?

Thank you for your kindly help.

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IanP

Joined: 05 Oct 2004
Posts: 6490
Helped: 1542
Location: West Coast

06 Nov 2004 3:35 Re: [Q]HOW to measure the square wave length ??

This is only an example how can you do it...

Connect this signal to Int0.
This will be activated on the falling edge.
Negate this signal and connect to Int1.
This will be activated on the rising edge of your original signal.
Start software counter1 on Interrupt 0 .. stop it on Interrupt 1.. start software counter2 on Interrupt 1 and stop it on interrupt 0 ...and so on

cetc1525

Joined: 08 Oct 2004
Posts: 177
Helped: 3

06 Nov 2004 10:24 [Q]HOW to measure the square wave length ??

can you use square pulse to test the length?

masai_mara

Joined: 13 Aug 2004
Posts: 118
Helped: 6

10 Nov 2004 8:12 Re: [Q]HOW to measure the square wave length ??

You can also do this way- make a counter(hardware) and enable it to run whenever the signal A is high. But you have to run this counter with a clock frequency much higher than signal A frequency.

IanP

Joined: 05 Oct 2004
Posts: 6490
Helped: 1542
Location: West Coast

10 Nov 2004 9:01 Re: [Q]HOW to measure the square wave length ??

It looks like you will need two counters: one to count T1, T3.. and second to count T2, T4...
They can be fed of the same generator. Your problem will be how to capture the count as next pulse,T3, will overwrite count of T1.

You see, with a microcontroller you can capture the whole sequence and then read it from the micro memory; harware solution is also possible but not feasible and quite tricky...