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Re: [Paparazzi-devel] Sensirion SHT75 on APOGEE

From: alexandre bustico
Subject: Re: [Paparazzi-devel] Sensirion SHT75 on APOGEE
Date: Sat, 17 May 2014 09:12:49 +0200

when timing is important, stm32 line offer bitbanding alias :

Bit Banding: Maps a complete word of memory onto a single bit in the
bit-band region. For example, writing to an alias word will set or
clear the corresponding bit in the bitband region. This allows every
individual bit in the bit-banding region to be directly accessible from
a word-aligned address, and individual bits to be toggled from C/C++
without performing a read-modify-write sequence of instructions

All the registers and the static ram has an alias map for
efficient bit manipulation. 

if i remember well, number of cycles to toggle an individual bit 
take 100 cycles with read/modify/write port method, and 10 with


Le Fri, 16 May 2014 23:07:37 +0200,
Felix Ruess <address@hidden> a écrit :

> Hi,
> if the timing of the bitbanging is not a problem it should be fairly easy
> to rewrite the driver to use mcu_periph/gpio (which is the same on lpc21
> and stm32) instead of direct register access...
> Cheers, Felix

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