How to output a square wave clock in the MHz range

Official Hardware Nano Family Classic Nano
1

Hi, I have a question regarding the NANO device. I want it to operate together with another high-speed device, and I would like the two devices to operate synchronously, so I can keep them generally in step with one another. The other device (a UPduino from TinyVision.ai) runs at 12/24/36/48 MHz, and can accept an external clock. I also can manipulate the clock with an internal phase-locked loop (PLL). However, the fastest "clock" I can find a way to extract from the NANO is through the "tone" command, and it can only output up to 32767 KHz (because the frequency is specified via a signed int); 30 KHz would multiply up to 12 MHz with a factor of 400, which is too high to be stable. Is there any way to output a higher frequency -- something at or closer to the NANO's clock frequency?

2

Nano can provide square signal at half of its main clock so it is 8MHz.

Like this:

void setup()
{
// ...
	pinMode(9, OUTPUT);

	OCR1A  = 0;
	ICR1   = 1;
	TCCR1A = _BV(WGM11) | _BV(COM1A1);				
	TCCR1B = _BV(WGM13) | _BV(WGM12) |_BV(CS10);
// ...
}
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3

Thanks! How do I do that?

4

See the edit of my previous post. It is for ATmega328P and similar - Arduino UNO and Nano.

5

I'll give that a try. Once again, thanks!

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6

Will the duty cycle of that 8 MHz signal be 50% to meet OP's requirement?

7

[GolamMostafa] I tested it, and it is 50%.

Now I need to check it out further, because I'm not familiar with these signals (TCCR1A, COM1A1, WGM12, CS10, etc.). Also, function _BV().

How do I change the output pin?

I think 8 MHz will work well for me, but are there other frequencies possible (e.g., 4, 2, 1 MHz)?

Will it interfere with any standard functions (delay, I2C, PCI, interrupts, etc.)?

Again, thanks much.

8

1. TCCR1A (consult data sheets for the detailed meanings of the bits)
TCCR1Ax

2. TCCR1B
TCCR1Bx

3. _BV(CS10)
The above function places HIGH at CS10 (Clock Slect Bit-0 of Timer/Counter 1 (TC1))

4.

PWM signals are available on the following designated DPins of Arduino UNO - 6, 5; 9, 10; 11, 3.
pwm328-1

5.

(1) PWM signal can be generted in various modes as listed in the following Table.

waveformMode
waveformMode789×607 203 KB

(2) For Mode-14, the following equation is valid:

f = 16000000/(N x (1 + TOP)) //N and TOP are variables to get different frequencies


f = frequency in Hz
N = TC1 Clock Prescaler (/1, /8, /64, /256, /1024) determined by CS12-CS10 bits)
TOP = ICR1, then duty cycle can be chnaged by OCR1 Register.
TOP = OCR1A, then duty cycle can be changed by OCR1B Register.

6.

Please, figure out from the following diagram by looking into the alternate functions of the pins:
pinAT328p

DPin numbers for the IO lines are:
PD0 - PD7 : 0 - 7
PB0 - PB5 : 8 - 13
PC0 - PC5 : A0/14 - A5/19

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9

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