CubeMX timing

[e d]

Posted on June 07, 2017 at 20:18

Hi guys,

I am running into some timing issue using CubeMX, probably after upgrading to the latest version. A couple of weeks ago I noticed my SysTick running roughly twice as fast as expected (half of 1ms) so I changed my 1ms systick to Timer2 which worked fine. Today I turned on my USART3 for the first time at 9600 BAUD and could not get the HyperTerm to receive correctly (all garbage). Then I took a closer look at the signal through the scope and noticed the BAUD was actually at about 23KBAUD, which was weird because I set it in the code as:

huart3.Init.BaudRate = 9600;

After mucking around I got the HyperTerm to work normally by changing the BAUD setting to:

huart3.Init.BaudRate = 4000; // This is actually 9600 BAUD (verified with scope)

I have a hunch the BAUD rate issue is related to the SysTick issue.Anyone has this issue or is familiar with CubeMX to give me a clue here?

Thanks,

ED

Note: this post was migrated and contained many threaded conversations, some content may be missing.

[e d]

Posted on June 08, 2017 at 18:36

It is 1.8.0.

I must add that I had developed the current code using the previous version, then upgraded the CubeMX version and did a ''Generate Code'' on top of the existing project. If that makes any difference...

[e d]

Posted on June 08, 2017 at 23:59

Any clue?

[Zt Liu]

Posted on June 09, 2017 at 01:22

I will check it later on dev kit this afternoon.

For the moment you may try to generate the a new cubeMX project,

make no other setting except just rcc external crystallike your above picture.

Then toggle a gpio with a HAL_Delay in between. Check if it's fine.

(If it's not working, guess you really need check registers in the situation.)

[Zt Liu]

Posted on June 09, 2017 at 07:51

hi, Ed,

I used a STM32 nucleo board with L476 to make a test.

I got no 2MHz crystal, so I choose a rarely seen 9.8304MHz as the HSE clk source.

Everything works fine for me. I mean uart and systick.

My clk tree

Uart also works.

________________ Attachments : rcc and systick check.rar : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006HycK&d=%2Fa%2F0X0000000bA9%2FtSTDe6hlMnrbjxwFjPpk1THE3PV29Jnw0Fz8pmVv724&asPdf=false

[e d]

Posted on June 13, 2017 at 22:36

I can confirm that generating the SPI2 code using HAL instead of LL fixes the issue of SysTick timing and UART BAUD rate anomalies. This is quite disturbing as a programmer so can anyone let me know if this is an intended behavior?!?

[Zt Liu · Accepted solution]

Posted on June 14, 2017 at 06:06

I think I found why this would happen.....

using HAL library, here my Crystal is 9.8304MHz

in file stm32l4xx_hal_conf.h , you can find this macro

#if !defined (HSE_VALUE)

#define HSE_VALUE ((uint32_t)

9830400U

) /*!< Value of the External oscillator in Hz */

#endif /* HSE_VALUE */

Once you choose LL drivers, the project includesstm32l4xx_ll_rcc.h

Unfortunately, the macros in stm32l4xx_ll_rcc.his still as followed:

#if !defined (HSE_VALUE)

#define HSE_VALUE 8000000U /*!< Value of the HSE oscillator in Hz */

#endif /* HSE_VALUE */

If you manually modify this value to your crystal's frequency,

If you define the HSE_VALUE in the project setting (thanks

meyer.frank

‌ for reminding this!)

for example, in keil,

Everything would work as you expected!

🙂

Guess we need ST guys to fixed up the library.

[AvaTar]

Posted on June 14, 2017 at 07:52

 ,

 ,

Guess we need ST guys to fixed up the library.

I would not bet on that - this issue was already present in the 'old' Standard Peripheral Libs.

Instead of throwing an error (' ♯ error 'define a HSE_VALUE !'), these guys presumed to define a default.

This threw many users off the track initially ...

The best place to define HSE_VALUE would be your project settings (or a make file).

Editing the header file is not a good option.

[e d]

Posted on June 16, 2017 at 17:49

Why are these ST guys so neglectful of a long standing issue? They could have saved us our precious development time and undue stress with a simple change in the library. This is my first time using ST products and I don't have a good first impression.

Thanks all for your help!

[Tesla DeLorean]

Posted on June 16, 2017 at 21:06

On the other hand when they get it 100% right all the time they'll be able to replace you with a robot.

[e d]

Posted on June 17, 2017 at 14:07

Funny you mentioned robot 'cause I often wonder if you are one yourself