STM8S - SPI not working after power-on reset (yes, it strange)

Forum|Forum|14 years ago
March 19, 2012
4 replies
3268 views

Posted on March 19, 2012 at 19:01

I trying to develop device using STM8S105K6 MCU and found something very strange.

If I press reset button (connecting NRST to GND) all if working fine.

But If I just turn off/on device power, MCU is starting (timer is working, LED is flashing, and so on), but SPI is not working (to be more exact, it not clears TXE flag).

This is my code for init:

SPI_CR1_bit.BR = 1;

SPI_CR1_bit.MSTR = 1;

SPI_CR1_bit.CPOL = 0;

SPI_CR1_bit.SPE = 1;

This is a little bit later in main:

SPI_DR = 0x55; // test

while (!SPI_SR_bit.TXE) { // here we got infinite loop :(

PB_ODR_bit.ODR5 = 1;

PB_ODR_bit.ODR5 = 0;

}

If I do manual reset, all is starting to work fine. But If I just turn power off/on, it goes to infinite loop inside WHILE (and I can see this by oscilloscope by changing voltage on PB5 pin).

Another fact: If I will heat MCU by soldering iron or soldering station - it starting to work, but then it makes cold, and not working again.

Where is my problem (I hope not in my DNA :)?

What I should do to get stable working of MCU?

Thanks in advance!

#problem #reset #spi #stm8s

This topic has been closed for replies.

oleg239955_stAuthor

Associate II

Posted on March 19, 2012 at 20:08

Hmm..

I have tried to add ~5ms delay between initialization of MCU and SPI, and all started to work even in power-on sequence!

I still not understand what happened and why.

What is right workaround for this?

Stm32User

Associate III

Posted on April 24, 2012 at 14:20

Strange behaviour like this is often power supply related. If the problem occurs only when you cycle the power and is 'fixed' with a delay then the problem is related to the rise time of the power supply and/or power on reset of the device