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My objective is to write bare metal assembly code for STM32F103 that turns PB1 LED on.

ussrback
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1 Answers1

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Update: Reset value of every register is mentioned on top of the register in Reference Manual (Attached is snap below). enter image description here

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Wherever there are multi-bit parameters in registers, I am making a habbit of clearing them first and then applying a desired NON Zero value.

In case of setting Zero values, there is no need for clearing them. You are already clearing it.

here is a sample code i use.

////Clearing the bit masks. Need to keep it a practice at all multibit parameters
GPIOA->CRL=(GPIOA->CRL & ~((3U<<GPIO_CRL_CNF7_Pos) | (3U<<GPIO_CRL_CNF5_Pos)))
        | (2U<<GPIO_CRL_CNF7_Pos) | (2U<<GPIO_CRL_CNF5_Pos);//setting desired values

Here in above code, I want to set Configuration of PA7 & PA5 to Alternate Port function (Push-Pull).

So I cleared those bits and then set the desired value.

If i wanted to set a Zero in these bits, then I can simply write as below (Written for PC13)

GPIOC->CRH |= (GPIOC->CRH & ~(1U<<GPIO_CRH_CNF13_Pos)) | (2U<<GPIO_CRH_MODE13_Pos);     //LED PIN
Srikanth Chilivery
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