STM CircleOS forum / Bit Band Alias

primagen · 2011-03-14 01:16:25

Is it possible to make bit operation with alias?
For Toggle led i use this:
void led_toggle(GPIO_TypeDef* GPIOx, uint32_t GPIO_BSRR_BSx )
{
GPIOx->ODR ^= GPIO_BSRR_BSx;
}

but how it works with:
#define PB6 (*((volatile unsigned long *) 0x42218198 ))
PB6^=1; doesnt work

yrt · 2011-03-14 08:05:05

I did not get the same result for the alias address.

The formula is :
bit_word_addr = bit_band_base + (byte_offset x 32) + (bit_number × 4)

In your case :
bit_band_base = 0x4200 0000
byte_offset = 0x10C10 (GPIOB = 0x4001 0C00, GPIOx_BSRR = 0x10)
bit_number = 0x06

So, the result is 0x420218218 !?!

Take a look at some examples in this topic :
http://www.stm32circle.com/forum/viewtopic.php?id=1080

primagen · 2011-03-14 22:44:05

Hi,

I think you make an mistake for "byte offset".

Its 10C0C.
The problem is not the use of PB6=1 or PB6=0
I want to make bit operations on these defines like above

yrt · 2011-03-15 07:24:31

Ok,

The address is 10C0C for ODR register, 10C10 for BSRR
It seems that it was working for "sentinel" as indicated in the post before.

primagen · 2011-03-15 15:00:01

working for sentinel ?? What does this mean....
To my problem:
Am i able to use bit operation if i make pointer to BSRR alias??

yrt · 2011-03-16 07:05:03

I was just talking about the guy who posted these informations :http://www.stm32circle.com/forum/viewtopic.php?id=1080 !
I think it should be working with BSSR or ODR.

# 1 2011-03-14 01:16:25 Bit Band Alias

Bit Band Alias

# 2 2011-03-14 08:05:05 Bit Band Alias

Re: Bit Band Alias

# 3 2011-03-14 22:44:05 Bit Band Alias

Re: Bit Band Alias

# 4 2011-03-15 07:24:31 Bit Band Alias

Re: Bit Band Alias

# 5 2011-03-15 15:00:01 Bit Band Alias

Re: Bit Band Alias

# 6 2011-03-16 07:05:03 Bit Band Alias

Re: Bit Band Alias

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