Subject:
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Re: Piezo Rate Gyro and HB
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Thu, 9 Dec 1999 17:53:49 GMT
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Original-From:
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Thomas Hauri <thomas.hauri@zhwinAVOIDSPAM.ch>
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Viewed:
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3754 times
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Hi Jan
good job. I've done exactly the same thing :)))) I only use some assembler code to measure the time. In fact I have
some code, that lets you measure a frequency or a pulsewidth ranging from about 30 Hz to 30kHz.
If anyone wants the code (i've supplied it many times to other people from ths list) just send me a mail.
Unfortunately Fred hasn't put the code on the HB home page yet, maybe sometime he will :)))) (hi Fred)
cu
Tom
Jan Liphardt wrote:
> Hi,
>
> FYI, it is possible (and indeed pretty easy) to attach a small piezo
> rate
> gyro to the HB. I used the hitec GY-130 (availible for about 100$ from
> Tower Hobbies). It modifies a PWM signal - the pulse width increases or
> decreases depending on the rate of rotation around the gyro axis.
>
> I used one servo port on the extension board to provide the
> PWM signal:
>
> init_expbd_servos(action) ; /*initialize servos*/
>
> pos_servo_0 = 1500; /* 0 to 3000 are valid */
>
> and measured the pulse width with TIC3:
>
> while(1)
> {
> temp = gyro_sample();
> if((temp < 5000) && (temp > 100)) {printf("gyro rate: %d\n",temp)}
> sleep(0.1);
> }
>
> int gyro_sample() {
> int start_pulse;
> int end_pulse;
>
> int TFLG1 = 0x1023; /* Timer flags, 8-bit reg*/
> int TMSK1= 0x1022; /* Timer Interrupt Masks, 8-bit reg*/
> int TCTL2 = 0x1021; /* Timer control 2, 8-bit reg, interupt
> edge*/
>
> bit_set(TCTL2, 1); /* at tctl2, */
> bit_clear(TCTL2, 2); /* set tic3 for rising edge */
>
> poke(TFLG1, 1); /* clear tic3 flag */
>
> while (!(peek(0x1000) & 0x1)) { /*do nothing*/; }
>
> start_pulse = peekword(0x1014); /* tic3 has time of echo */
>
> bit_set(TCTL2, 2); /* at tctl2, */
> bit_clear(TCTL2, 1); /* set tic3 for falling edge */
> poke(TFLG1, 1); /* clear tic3 flag*/
>
> while (peekword(0x1014) == start_pulse){ /*do nothing until 0x1014
> actually changes*/; }
>
> end_pulse = peekword(0x1014); /* tic3 has time of echo */
>
> if ((end_pulse <0) && (start_pulse < 0 ))
> { return (end_pulse + (- start_pulse));}
>
> if ((end_pulse > 0) && (start_pulse > 0 ))
> { return(end_pulse - start_pulse); }
>
> if ((end_pulse <0) && (start_pulse > 0))
> {return( (32767 + end_pulse) + (32767 - start_pulse) );}
>
> if ((end_pulse >0) && (start_pulse < 0 ))
> {return ( (end_pulse) + (- start_pulse) ); }
>
> }
>
> Sorry about the terrible code - I've only had my HB since yesterday! It
> does work,
> though.
>
> Jan
>
> Jan Liphardt
> Dept. of Physics
> UC Berkeley
> (510) 642 1440
--
Thomas Hauri
ZHW Zuercher Hochschule Winterthur
Zurich University of applied sciences
IMS Institute of Mechatronic Systems
Technikumstr.9 /PF
CH-8401 Winterthur
Switzerland
Phone : +41 52 267 74 79
Fax : +41 52 268 74 79
Mail : Thomas.Hauri@zhwin.ch
HP : http://www.zhwin.ch
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