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plover

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Joined: 18/04/2013
Location: Australia
Posts: 305

Posted: 06:47pm 21 Apr 2016

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I have been thinking about a form of square wave generator, just a bit different to what can be found on ebay (Part of simple DDS offerings for example).

1.. Size and power a bit of a problem, as I would like it to be portable.
2.. Simple simple form, Micro SD card pushed in and it is all go (whatever this ends up being) Frequency change made on SD card.
3.. Later Squeeze in later 'communications' panel.
Seems that Mini/micro USB connect would also be advantage, not sure of its use just yet.

Comes to mind that some micros runs with very few components the question at this stage how high in frequency could this be made to run before RF technique would be considered in the layout?

Initially I would be very happy with getting to 10 MHz.

If the micro can do this, there will be a need for a good power amplifier able to provide 0 to 50V swing and at a guess 5 mA max.

What frequency range can be expected?

matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 10181

Posted: 10:21pm 21 Apr 2016

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Quote What frequency range can be expected?

What is the requirement?
10MHz is doable on a uP but 9.9 is not. Possible frequencies might go something like 10, 6.67, 5, 4 ...

plover

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Joined: 18/04/2013
Location: Australia
Posts: 305

Posted: 03:23am 23 Apr 2016

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matherp
You have got me there, I don't follow. I think I have explained it badly.

What I require is something working a bit like a 555 timer, Output pin on for 1 second off for 1 second or on for t1 seconds and off for t2 seconds. Initially t1=t2 (but I can see a time where I need t1 and t2 to be different).

I would like to use a micro because I am looking at it as a variable square wave generator which can be set to a given frequency. though this will soon be required to scan automatically or should I say sweep automatically.

I am pretty sour that quite some time ago micros have been used to simulate the 555 chip to a degree, this was the 8 legged micros. In this case more legs will be handy as development goes ahead.

My question is the "standard" micros here in forum, how hard can they be pushed fo upper frequency? If the clock frequency is 20 MHz say can I get 10 MHz out?

MicroBlocks

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Joined: 12/05/2012
Location: Thailand
Posts: 2209

Posted: 03:55am 23 Apr 2016

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This looks like a good candidate for the PWM capable pins.
Lots of mcu's have PWM peripherals.
With a uMite you can go from 20Hz to 500Khz with any duty cycle.
Using the mcu directly you can get higher frequencies but it depends on which specific mcu.

I think with a PIC32 it is a maximum of 10Mhz with a 80Mhz clock.

Microblocks. Build with logic.

matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 10181

Posted: 06:33am 23 Apr 2016

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Quote You have got me there, I don't follow

The point I'm making is that the output frequency has to be a divisor of the clock frequency so 40MHz/4=10MHz, 40MHz/5=8MHz etc. 9.9MHz is completely impossible if this is a requirement

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