How to use external crystal?

[gocchan]

Hi,

I want to run STM8S003F with an external crystal.

How do I use APIs in stm8_clk?

Or in which material is it described?

Regards,

Gotoda

[Peter BENSCH]

The first resources to read are the RM0016 reference manual, where to search for HSE (High-Speed External Oscillator), and the STM8S003 datasheet.

Then check the Standard Peripheral Firmware Library (SPL) STSW-STM8069, which contains some user manual, describing the function to enable the HSE. And finally you can also check this SPL for the files stm8s_clk.c and stm8s_clk.h, where you will find the function CLK_HSECmd(ENABLE).

Good luck!

If the problem is resolved, please mark this topic as answered by selecting Select as best. This will help other users find that answer faster.

/Peter

[WilkoL]

Also read application note AN2752, It even has a reference Design (chapter 7)

[gocchan]

I implemented the following code to see if the external clock works, but I couldn't observe the clock.

void main(void)
{	
	CLK_DeInit();
	CLK_HSECmd(ENABLE);
	while(1);
}

Are there any missing implementations or configs?

[gocchan]

When implemented as follows, it was confirmed that 2MHz was output from the PC4 (CLK_CCO) terminal, but no clock waveform was observed at the OSCOUT terminal.

void main(void)
{
	CLK_DeInit();
	CLK_ClockSwitchConfig(CLK_SWITCHMODE_AUTO, CLK_SOURCE_HSE, DISABLE, CLK_CURRENTCLOCKSTATE_DISABLE);
	CLK_HSECmd(ENABLE);
	CLK_ClockSecuritySystemEnable();
	CLK_CCOConfig(CLK_OUTPUT_HSE); //View output via PC4
	CLK_CCOCmd(ENABLE);
	while(1);
}

I checked the voltage waveforms of OSCOUT and OSCIN with an oscilloscope, but I could not observe 16 MHz.

I am using a 16MHz xtal with 12pF capacitors and 0 ohms resistor.

How can I code this crystal to oscillate?

[WilkoL · Accepted solution]

So you see a signal on CLK_CCO. That means that either the crystal oscillator or the internal RC oscillator is functional. Since you see a 2 MHz signal that suggests that it is the internal RC oscillator, as by default its 16 MHz freq is divided by 8. And you do not divide the CLK_CCO signal. The odd thing is that you select HSE as the CLK_CCO signal, that doesn't make sense.

Can you give the code below a try? It works for me, although I did not have a 16 MHz crystal, but used an 8 MHz one.

The oscilloscope shows a (small) 8 MHz signal on both PA1 and PA2, Make sure to use a probe that doesn't load the oscillator too much (10x probe)

void HSE_config(void)
{
  CLK_DeInit();
  
  CLK_HSECmd(ENABLE);
  CLK_LSICmd(DISABLE);
  CLK_HSICmd(DISABLE);
  while(CLK_GetFlagStatus(CLK_FLAG_HSERDY) == FALSE);
 
  CLK_ClockSwitchCmd(ENABLE);
  CLK_SYSCLKConfig(CLK_PRESCALER_CPUDIV1);
 
  CLK_ClockSwitchConfig(CLK_SWITCHMODE_AUTO, CLK_SOURCE_HSE, 
  DISABLE, CLK_CURRENTCLOCKSTATE_ENABLE);
 
}
 
void CLOCK_output(void)
{
	CLK_CCOConfig(CLK_OUTPUT_CPUDIV8);
	CLK_CCOCmd(ENABLE);
	while(CLK_GetFlagStatus(CLK_FLAG_CCORDY) == FALSE);
}

[gocchan]

I can't get out of the CLK_GetFlagStatus() loop.

CLK_ECKR value is 0x01 (HSE clock on but not ready).

CLK_ICKR is 0x03.

Is there a hardware (our custom board) cause?

[WilkoL]

It means that you enabled power to the HSE, but it isn't oscillating. And because you had the line

CLK_ClockSecuritySystemEnable();

in your code, the MCU switched back to the HSI.

So yes it looks like there is something wrong with the hardware, perhaps a crystal that is broken. Have you tried replacing it? Are the capacitors of the right value?