LSM9DS1处于只写模式如何读取磁力计值？

我认为CTRL_REG3_M的条目中有一个令人震惊的错字。什么用途是只写SPI设备？大声笑！幸运的是，手册中的其他地方表明SIM位（为什么称为SIM？）控制磁力计是处于4线模式（0）还是3线模式（1）。
我怀疑CTRL_REG3_M条目的作者试图说明** SDI **（不是SPI！）是否可用于输出和输入（3线模式，将该位设置为1）或仅用于输入（4 -wire mode，将该位设置为0）。
在这个主题上，我刚刚发现在我的应用程序中，我需要先将0写入此位，然后才能在4线模式下从器件读取。数据表说0是SIM位的默认值。但是，如果我在4线SPI系统上电后尝试读取WHOAMI，除非我首先写出所谓的“默认”值，否则它将无法工作
CTRL_REG3_M到该寄存器。
因此，我怀疑CTRL_REG3_M的条目中不仅存在打字错误，而且SIM位的默认值也可能存在错误。



以下为原文




I think there's an egregious typo in the entry for CTRL_REG3_M.  What use is a write-only SPI device?  LOL!  Luckily, elsewhere in the manual it indicates that the SIM bit (why is it called SIM?) controls whether the magnetometer is in 4-wire mode (0) or 3-wire mode (1).
I suspect the author of the entry for CTRL_REG3_M was trying to say whether **SDI** (not SPI!) is usable for output as well as input (3-wire mode, set the bit to 1) or for input only (4-wire mode, set the bit to 0).
On this topic, I have just found that in my application, I need to write 0 to this bit before I can read from the device in 4-wire mode.  The data sheet says 0 is the default value for the SIM bit.  But if I try to read WHOAMI after power-up in a 4-wire SPI system, it won't work unless I first write the supposed 'default' value of
CTRL_REG3_M to that register.

So, I suspect that not only is there a knee-slapper of a typo in the entry for CTRL_REG3_M, there may also be an error in the default value for the SIM bit.