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cosmic frog
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Posted: 07:55am 20 Apr 2020

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On the 28 pin Micromite I'm using PWM 2,freq,2A.
This should send a frequency to Pin26.
If I added ,2B (ie. PWM 2,freq,2A,2B) this should send a frequency to Pin26 and Pin24.
I seem to be getting something on Pin24 just by using 2A. I know this because I have a 16x2 LCD connected to this pin and when I send a frequency to Pin26 it effects Pin 24 and corrupts the display.

From page 44 of the manual- "The specified I/O pin will be automatically configured as outputs while any others will be unaffected and can be used for other duties."

I'm using v5.05.02

Thanks.

Dave.
Edited 2020-04-20 18:00 by cosmic frog

goc30

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Posted: 08:43am 20 Apr 2020

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Hi cosmic

PWM 2B use pin24 for output. for that, you send "something" on this pin when you declare PWM2B

cosmic frog
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Posted: 08:59am 20 Apr 2020

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goc30 said Hi cosmic

PWM 2B use pin24 for output. for that, you send "something" on this pin when you declare PWM2B

Hi Goc.
I am only sending output to 2A (pin26)
I'm not sending anything to 2B (pin24)

Thanks.

Dave.

goc30

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Posted: 09:34am 20 Apr 2020

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cosmic frog said

Hi Goc.
I am only sending output to 2A (pin26)
I'm not sending anything to 2B (pin24)

Thanks.

Dave.

but you put "PWM 2,freq,2A,2B" in your prog
in this case proc send pulses on pin 26 and pin 24 (with same freq and same cycle)

matherp
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Posted: 09:48am 20 Apr 2020

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I've checked the code and no apparent bug

Try the following

Connect pin 24 to pin 15 and run the code:

SETPIN 15,CIN,PULLUP
PWM 2,1000,50
PAUSE 1000
PRINT PIN(15)

cosmic frog
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Posted: 05:18pm 20 Apr 2020

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goc30 said

cosmic frog said

Hi Goc.
I am only sending output to 2A (pin26)
I'm not sending anything to 2B (pin24)

Thanks.

Dave.

but you put "PWM 2,freq,2A,2B" in your prog
in this case proc send pulses on pin 26 and pin 24 (with same freq and same cycle)

You need to re-read my post.

cosmic frog
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Posted: 05:20pm 20 Apr 2020

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matherp said I've checked the code and no apparent bug

Try the following

Connect pin 24 to pin 15 and run the code:

SETPIN 15,CIN,PULLUP
PWM 2,1000,50
PAUSE 1000
PRINT PIN(15)

I'll give it a try. Thanks.

panky

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Posted: 05:17am 21 Apr 2020

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@cosmic frog,

I can not see any issue with any crosstalk between the two outputs of PWM channel 2 on a 28 Micromite running 5.05.02. Have you checked that you don't have either a short somewhere between pins 24 and 26?

The only issue I can see is that once a PWM channel starts, it continues to output until a PWM channel,STOP is issued. So, if for example, you issue the command

PWM 2,1000,50,30

... you get a 50% square wave on pin 26 (2A) and a 30% (2B) square wave on pin 24, which is of course, correct operation. If you now decide to use the first output (pin 26 or 2A) only for PWM and now issue the command

PWM 2,1000,10

... you get a 10% sqaure wave on pin 26 but the output on pin 24 (the 30% square wave) continues until you either reset the MM or issue a PWM 2,STOP command. Note that this will kill BOTH 2A and 2B outputs (pins 26 and 24 respectively).

As an aside, there does not appear to be a way to utilise the 2B output only as the command

PWM 2,1000,,50 throws a syntax error.

So a question for Geoff or Peter is, how can the second output of PWM channel 2 on pin 24 (2B) be utilised for PWM action while using the primary output (2A on pin 26) for some other I/O function?

panky

... almost all of the Maximites, the MicromMites, the MM Extremes, the ArmMites, the PicoMite and loving it!

cosmic frog
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Posted: 08:15am 21 Apr 2020

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Hi Panky and thanks for the reply.
Just been doing some more tests and found that the 'bug' happens when you
use PWM 2,STOP.
So there is no signal on pin24 with PWM 2,freq,50 but if I try to stop it with
PWM 2,STOP I see corruption on my LCD.

The workaround for this is to use something like PWM 2,90000,0 insted of PWM 2,STOP.

I think what is happening is, it assigns pins 26 and 24 with PWM 2 and with PWM 2,STOP it releases the pins back to a undetermined state, corrupting the LCD. Maybe?

Thanks.

Dave.

Edit.
Just putting PWM 2,STOP in my program corrupts the LCD.
Edited 2020-04-21 18:21 by cosmic frog

matherp
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Posted: 08:50am 21 Apr 2020

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This does look like a bug in PWM stop- I'll email Geoff

goc30

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Posted: 09:39am 21 Apr 2020

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matherp said This does look like a bug in PWM stop- I'll email Geoff

is it possible that it is same pb as I have with digital pot and values not correct ?? (see https://www.thebackshed.com/forum/ViewTopic.php?FID=16&TID=12049&LastEntry=Y#145116)

matherp
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Posted: 02:03pm 21 Apr 2020

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Quote is it possible that it is same pb as I have with digital pot and values not correct

Only if you are using PWM pins other than the first one for a specific purpose and have issued a PWM STOP command for that channel

goc30

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Posted: 02:27am 22 Apr 2020

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matherp said

Only if you are using PWM pins other than the first one for a specific purpose and have issued a PWM STOP command for that channel

Sorry but I have changed my CS pin (pin22 in place of pin26). and I have same probl�me

goc30

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Posted: 11:20pm 22 Apr 2020

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matherp said

Only if you are using PWM pins other than the first one for a specific purpose and have issued a PWM STOP command for that channel

I found the origin of my value imprecision problem with digital pot.
this comes from the fact that I had not wired the 8Mghz quartz (with 2x22pf), so everything was more or less unstable. With quartz it became correct

Geoffg

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Posted: 09:02am 28 Jun 2020

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panky said So a question for Geoff or Peter is, how can the second output of PWM channel 2 on pin 24 (2B) be utilised for PWM action while using the primary output (2A on pin 26) for some other I/O function?

Sorry, I just discovered this question.

The answer is that you cannot. You must use 2A first, then 2B can be used or not.

Geoff

Geoff Graham - http://geoffg.net

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