Question about USART??

[elaroussi]

Posted on February 21, 2014 at 16:17

PLz can some one tell me why we must ''&'' the received value with 0x7F!!!!!!

[chen]

Posted on February 21, 2014 at 17:04

''PLz can some one tell me why we must ''&'' the received value with 0x7F''

There is no absolute need to bit wise AND with 0x7F! It is probably there to support 7bit data width for the RS232 standard.

[Tesla DeLorean]

Posted on February 21, 2014 at 17:20

It is probably there to support 7bit data width for the RS232 standard.

Or strip parity, ST's definition of data bit includes the parity bit, the USART_DR can contain up to 9-bits. Masking covers a couple of ill's including stopping some compilers warning as you cast from a 16-bit unsigned int to an 8-bit signed/unsigned char. There is generally much disagreement as to whether a char is signed or unsigned, many compilers/os have their own ideas, with defaults, or overrides.

[elaroussi]

Posted on February 21, 2014 at 23:31

thks 4 help 🙂