[SOLVED] generator on a timer with an interval of 25 nanoseconds ?

Tell me a simple code example for the squarewave generator on a timer with an interval of 25 nanoseconds (25 MHz)
Board STM32F407 BLACK.

Did so, but at least 1 microsecond. It should be faster !

void setup()
{
timer.pause();

timer.setPeriod(1);
timer.setChannel1Mode(TIMER_OUTPUT_COMPARE);
timer.setCompare(TIMER_CH1, 1);
timer.attachCompare1Interrupt(timer_interrrupts);
timer.refresh();
timer.resume();
}

void timer_interrrupts()
{
if (digitalRead(PA2) == true)
digitalWrite (PA2, LOW);
else
digitalWrite (PA2, HIGH);
}

You should use directly the PWM output signal of timer instead of digital port output.
Add this line to setup() to generate PWM signal on a timer channel pin:
pinMode(OUTPUT_TIMER_CHANNEL_PIN, PWM);

25 Nano seconds is not 25MHz, it’s 40Mhz

You would probably need to set the clock PLL so the board ran at 160MHz so the timer can have a divider of 4.

Hello stevestrong !
I included the line pinMode(PA1, PWM) in setup().

What code is necessary to enter into
void timer_interrrupts()
{
???
}

for this to work ?

Hello RogerClark !

Whether correctly I understood You that it is necessary to do so ?
timer.setPrescaleFactor(4);

If not, tell me how to do it. I really need the PWM frequency is much faster than 1 MHz!

Depends on what resolution PWM you need

E.g. on the F103, with 8 bit resolution, max PWM rate will be 72/256 = approx 280 Khz is max PWM rate

On the F4 with 160 Mhz clock rate and 8 bit resolution PWM that only gives you a PWM freq 625 kHz

None of these boards will give you a PWM of period of 1Mhz. Except perhaps if you extremely overclock the processor to 256Mhz, and I’m not sure if anyone has successfully done that.

I think you’ll need to use something like a FPGA to achieve the sort of performance you are looking for

I understand You correctly, that the more frequency of 625 kHz at the timer without overclocking out any ways ?
I need a simple generator of rectangular pulses

And without the use of PWM it is possible to obtain a high speed of generation ?

Yes, you can obtain Mhz output in a pin by setting the reload value to 1, prescaler to 0, and timer compare to either 0 and 1.

The problem seems to be on the F4 side in the Roger’s (and my) repo.
I am investigating the issue, but it seems that major rework is necessary.

@acronis

You have written conflicting requirements.

You said 25nS interval. Which is possible using he F4 processor.

You also said 1MHz PWM, which is not possible ( assuming 8 bit PWM resolution)

I think you need to explain what you are trying to do, and why….

Good afternoon everyone.

I need to generate a square signal of 1 bit (output either 0 or 1 ) with high frequency using a timer.
The frequency of generation needs the most high , more than 1 MHz

Image https://yadi.sk/i/O_BCSslH3Qheba
( Tell me on what site to upload images so that they appear on the forum in the topic)

Try this:
#define timer Timer5

#define TIMER5_CH1_PIN PA0

void setup()
{
pinMode(TIMER5_CH1_PIN, PWM);
gpio_set_af_mode(TIMER5_CH1_PIN, 2);

timer.pause();
timer.setPrescaleFactor(1); // use 42MHz internal clock
timer.setOverflow(2); // output ~21MHz signal (48ns period)
timer.setCompare(TIMER_CH1, 1); // 50% duty cycle: 24ns low + 24ns high
timer.refresh();
timer.resume();
}


OK

So what is needed is a 20Mhz square wave.

Hello stevestrong !

I am very grateful for Your invaluable help in the study of this beautiful microcontroller STM32F407 !
It is not a rectangular generator, but I think this is what I need and will work fine from me !

Code I liked it, but I have a few questions for You:
1. I have not found information on the forum about the line gpio_set_af_mode(TIMER5_CH1_PIN, 2);
What does it do and what does the digit 2 ?

2. Is it possible to assign a different pin out ? For example PA2 ? I tried but I not working. How can I change ?

3. Is it possible to obtain even greater frequency generator, for example 84 or 100 or 168 MHz ?

I would be very grateful if You could help me with these newbie .

[acronis – Mon Dec 18, 2017 1:02 pm] –
…
3. Is it possible to obtain even greater frequency generator, for example 84 or 100 or 168 MHz ?
…

Probably not directly, but there are several ways you can double the frequencies you *can* generate, so long as you don’t mind adding a bit of extra hardware, for example with a couple of flip flops.

.. although I’m not sure if the humble CD4528 would be fast enough for your application, so you may have to do a bit of googling to find something suitable.

You could also look at the ad9851 dds signal generator, controlled by the STM32F103 of course

https://www.ebay.com/sch/i.html?_sacat= … dds&_frs=1

What is the purpose of this square wave?

Hi ahull.

Thanks for Your hint, but I’m not good friends with the construction of schemes and I don’t want to use any external components , and I want to only microcontroller .
The more code that has prompted dear sevestrong works fine.
Just want to deal with those questions that I wrote that I understood as with it to work correctly.

We are developing an interesting project to measure the percent alcohol.
To modify the desired generation.
First generated signal , and then analyze the response by the ADC of the microcontroller.
By the way ADC has me very helped sevestrong

[acronis – Mon Dec 18, 2017 1:02 pm] –
3. Is it possible to obtain even greater frequency generator, for example 84 or 100 or 168 MHz ?

If you just need a square wave, it should be possible to to output the system clock (up to 168MHz) via the MCO pins but I can’t provide you the technical details..

Cheers, E.

If you just need a square wave, it should be possible to to output the system clock (up to 168MHz) via the MCO pins but I can’t provide you the technical details..

And where can I see information ?

If anyone is interested, the measurement results look like this
https://yadi.sk/i/C05IOvNy3Qijun

[acronis – Mon Dec 18, 2017 1:02 pm] –
It is not a rectangular generator, but I think this is what I need and will work fine from me !

Well, it must be a square-wave signal, because it is a digital output PWM signal from timer 5 compare channel 1.

[acronis – Mon Dec 18, 2017 1:02 pm] –
gpio_set_af_mode(TIMER5_CH1_PIN, 2);

Well, it must be a square-wave signal, because it is a digital output PWM signal from timer 5 compare channel 1.

hmmm . But it’s not .Why …

With the oscilloscope

https://yadi.sk/i/Ly1g8RBe3QiqfN

Hello steve

I updated the library today to your last on F4.
on the previous version, this code worked fine – but now gives an error

invalid conversion from 'int' to 'gpio_af_mode' [-fpermissive]

Use GPIO_AFMODE_TIM3_5 instead of value 2
gpio_set_af_mode(TIMER5_CH1_PIN, GPIO_AFMODE_TIM3_5);

Steve. These options are compiled normally but the code

#include <Adafruit_TFTLCD_16bit_STM32.h>
Adafruit_TFTLCD_16bit_STM32 tft;

#define timer Timer5
#define TIMER5_CH1_PIN PA0

void setup()
{
tft.reset();
tft.begin(0x9341);
tft.setTextSize(1);
tft.setRotation(1);
tft.setTextColor(BLUE);
tft.fillScreen(BLACK);

pinMode(TIMER5_CH1_PIN, PWM);

// gpio_set_af_mode(TIMER5_CH1_PIN,GPIO_AFMODE_TIM3_5);

gpio_set_af_mode(TIMER5_CH1_PIN, (gpio_af_mode)2);

timer.pause();
timer.setPrescaleFactor(1); // use 42MHz internal clock
timer.setOverflow(2); // output ~21MHz signal (48ns period)
timer.setCompare(TIMER_CH1, 1); // 50% duty cycle: 24ns low + 24ns high
timer.refresh();
timer.resume();

}

void loop() {
tft.println("Test");
}

Oops, sorry.
My previous commit erroneously removed the predefined Timer instances.
I re-added them now.
Please check out my repo again.
(In the future please pay attention to the warnings printed by the Arduino IDE in the message window!)

Steve’s great !

Everything works as before !
Thank You!