Start Range 2 mode in STM32WB55

[KKIM.6]

I'm trying to use Range 2 mode in my custom STM32WB55 board to reduce power consumption in my board.

I found the protocol that switchs Range 1 to Range 2 mode in RM0434 document.

The basic protocol is like below and I found that three register should be changed to use Range 2 mode, which is RCC clock control, Flash ACR, and PWR control register (+PWR status register).

So, my question is how to change these registers and is there any example for change these or CubeMX to help change these value?

In addtion, I tried to change RCC clock using CubeMX but HCLK2 cannot be 16 MHz. Why?

[IIRHO.1]

Hello @KKIM.6 and welcome to ST Community.

go from Range 1 to Range 2 you have to:

• Reduce the system frequency to a value lower or equal to 16 MHz. as you can see bellow.

• Write 010 to the Bits 2:0 of the Flash_ACR register to have two wait states ( refer to the Table 4 of the RM0434).
• Write 10 to the Bits 2:0 of the PWR_CR1 register to select RANGE 2.

you can do this importing some modification on your code's source files. 

For your second question, the answer is in screenshot below.

Issam

[KKIM.6]

Still, my cubeMX shows error in HCLK2 in 16 MHz.

Where can I write Flash_ACR register and PWR_CR1 register? 

Should I use cubeProgrammer after importing program to the microcontroller?

[IIRHO.1]

Hello again

I suggest you to:

• Update your CubeMX to the last version.
• Is always better to change the registers value in your code before importing the program to the microcontroller.

Best Regards.

Issam

[KKIM.6]

I found that the use of RCC caused the problem in HCLK2. 

However, I cannot turn on RF if I do not use RCC. 

What should I do?

or is it not mandatory to use HCLK2 in 16 MHz?

[IIRHO.1]

Hello again,

You have to keep your system frequency to 16MHz or lower. But if you go lower you need to check the Table 4 in the RM0434 to make sure about the wait states.

Can you add your RCC Mode and Configuration

Best Regards

Issam

[KKIM.6]

I upgraded CubeMX in the 6.9.1 version but still the problem doesn't be solved.

Here is my RCC  configuration.

I created a new project and I'm changing each setup to find the reason.

[KKIM.6]

The error disappear when RF is deactivated......OMG..

[IIRHO.1 · Accepted solution]

Hello again 

After verification, is impossible to use RF communication in Range 2. Sytem clock in Range 2 should be under 16MHz but in RF transmittion CPU2 CLOCK must be 32MHz. What means system clock should be 32MHz.

Best Regards.

Issam

[KKIM.6]

That means....we cannot use BLE in range 2 mode...that's too bad.