LIS3DH ODR的输出数据速率是多少？

你好，
看看
http://www.st.com/resource/en/application_note/cd00290365.pdf
 （有7个'输出数据速率'项出现）。考虑一个采样率 - 你不能以比配置寄存器中设置的更高的速率获得更新的数据。如果使用FIFO，则将数据速率推入FIFO。



以下为原文




Hello,
have a look at the
http://www.st.com/resource/en/application_note/cd00290365.pdf
(there are 7 occurences of 'output data rate' term).Consider it a sampling rate - you can't get newer data at a higher rate than the one set in the configuration registers. If you use FIFO, it is the rate of data being pushed into the FIFO.

这绝不是一个愚蠢的问题。文档很不清楚，似乎使用ODR为1）一组4位ODR0-3引用CTRL_REG1（20h）第8节，其值可以是0到9或0到5376之间的数字。你永远不会得到除以0（因为没有列出的断电状态转换。
因为上电启动时间（表11）也列出了这个N / ODR数学，我们可以假设ODR是结束状态的速率（而不是当前状态）吗？如果我们使用这些位，这无关紧要，但如果我们使用Hz，则很重要。
另一方面，在同一文档的其他地方，ODR被称为采样率，以Hz为单位表示（如您所做）。
有一个应用笔记：AN3308，它会详细介绍。在4.3.1节中，它说HPF位的影响取决于ODR，但随后列出的变化以Hz为单位，而不是ODR位值。
AN3308的第6.1节确实使用了与转换时间相同的N / ODR算法，这里有一个例子，在这个例子中，它们似乎使用实际的Hz作为ODR值。这适用于持续时间，但也许我们可以假设其他N / ODR值意味着相同的事情。在任何情况下，他们都认为ODR的值为1到5376（这意味着ODR以HZ为单位）。这意味着转换时间非常短（在某些情况下为亚微秒），鉴于在数据表第3.2.1节中列出的正常模式下启动的1.6ms时间没有多大意义。
所以...也许我们只是使用最长的时间，然后它会工作。如果我们以0Hz运行，ODR位为0x1，并且我们从12位模式转换到8位模式，则两次计算都有1 ms（1 Hz和ODR位为1）。如果我们以12位运行，ODR位为0x9，则转换时间为1/9毫秒（112us）。或1/1344毫秒（0.75us），这似乎相当快（MEMS中的M是机械的！）。
 在任何情况下，对于我的应用程序，我将假设最长的时间是7 / ODR位（在7毫秒到7/9毫秒之间）。但如果我能正确使用它，而不是猜测，那肯定会很好。
 
数据表的第2.3节没有更清楚地说明这一点，该部分试图通过将读者引用到表25来澄清数学。遗憾的是，这与该事项没有任何关系。
在ST做数学的人怎么样？如果我们知道一个数字，整个事情就会变得清晰：
什么是工作模式从12位转换到8位且ODR设置为9才能启动的开启时间（在这种情况下，频率为1344Hz开始并以5376Hz结束。所以如果我们知道一次进入以毫秒为单位，我们可以回答所有这些问题的答案。
或者，也许我们可以得到一个答案，我们可以在计算7 / ODR中插入ODR的内容？ ODR是0-9吗？或者是ODR 0 - 5376？在后一种情况下，值是“结束状态值”还是ODR的起始状态值？



以下为原文




It is by no means a stupid question.  The documentation is quite unclear and seems to use ODR as 1) a set of 4 bits ODR0-3 refer to CTRL_REG1 (20h) section 8,  which can have values of 0 to 9 OR as a number between 0 and 5376. You never get a divide by 0 (because there are no transitions to power down state listed.
Because the power up Turn On times (table 11) also list this N/ODR math, can we assume the ODR is the rate of the end state (rather than the current state)?  This doesn't matter if we use the bits, but if we use the Hz, it matters.
On the other hand, elsewhere in the same document, the ODR is referred to as the sample rate, which is expressed (as you have done) in Hz.
There is an application note: AN3308, which does go into more detail.  In section 4.3.1 it says that the effect of the HPF bit depends upon the ODR, but then the listed variations are in Hz, not the ODR bit value.
Section 6.1 of AN3308 does use the same N/ODR arithmetic used in the transition time, and here there is an example and in that example they appear to use the actual Hz as the ODR value.  This applies to duration but perhaps we can assume that the other N/ODR values mean the same thing.  In any case they consider the ODR to be a value of 1 to 5376 (which means the ODR is measured in HZ). This would mean the transition times are very short (sub microsecond in some cases) which doesn't make much sense in light of the 1.6ms time to start in normal mode listed in section 3.2.1 of the data sheet .  
So... maybe we just use the longest time, and then it will work. If we are running at 1Hz with ODR bits of 0x1, and we transition from 12-bit mode to 8 bit mode, we have 1 ms with both calculations (1 Hz and ODR Bits are 1).  If we are running at 12bit with ODR bits of 0x9, then the transition time is either 1/9th of a millisecond (112us). or 1/1344th of a millisecond (0.75us) which seems pretty fast (the M in MEMS is mechanical!).
In any case, for my application I am going to assume that the longest timing is 7/ODR Bits (which is between 7ms and 7/9ths of a millisecond).   But it sure would be nice if I could use this correctly, instead of guessing.

None of this is made any clearer by section 2.3 of the data sheet which seeks to clarify the math by refering the reader to table 25.  Which unfortunately has nothing at all to do with the matter.
How about someone at ST doing the math.  The whole thing would become clear if we knew one number:
What is the Turn-on time for operating mode transition from 12-bit to 8-bit with the ODR set to 9 to start (in this case the frequency is 1344Hz to start and ends at 5376Hz.  So if we knew that one time in in milliseconds we could back into the answer for all of them.
Alternatively maybe we could get an answer on what do we plug into ODR in the calculation 7/ODR?  Is ODR 0-9?  Or is ODR 0 - 5376?  And in the latter case is the value the 'end state value' or the the starting state value of the ODR?

ODR是以Hz为单位的输出数据速率，因此请在公式中以Hz为单位输入值。
关于开启时间，要使用的ODR始终是目标（最终值）。



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ODR is Output Data Rate in Hz so please put the value in Hz in the formulas.
Concerning the turn-on time the ODR to be used is always the target one (end value).

米罗斯拉夫：非常感谢你，这极大地澄清了事情。布鲁斯



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Miroslav: Thank-you so much, that clarifies things immensely. Bruce