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Help needed to explain bit 8 on Gyro Sensor data transfur

 
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snow

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Joined: 28 Jun 2005
Posts: 166
Location: Ashburton / Mid Canterbury / New Zealand
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PostPosted: Mon Aug 05, 2019 1:35 am    Post subject: Help needed to explain bit 8 on Gyro Sensor data transfur Reply with quote
Hi
Just been looking at some code dealing with L3GD20 Gyro.
Could someone explain to me why bit 8 is set in this piece of code.

Code:
Read_Gyro:
   I2cstart
    I2cwbyte L3GD20_W
    I2cwbyte &B1010_0110                                    ' (OUT_TEMP AND &B10000000)  <--------------------

   I2cstart
    I2cwbyte L3GD20_R
    I2crbyte Temp , Ack
    I2crbyte Status , Ack
    I2crbyte Xl , Ack
    I2crbyte Xh , Ack
    I2crbyte Yl , Ack
    I2crbyte Yh , Ack
    I2crbyte Zl , Ack
    I2crbyte Zh , Nack
   I2cstop
 


Referring to the data sheet the out_temp reg is &B010_0110 (Reg26) page 35.
Is it something to do with when receiving multi bytes in one go with out stopping the bus??

Thanks
Snow

(BASCOM-AVR version : 2.0.7.5 , Latest : 2.0.8.2 )
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EDC

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Joined: 26 Mar 2014
Posts: 673

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PostPosted: Mon Aug 05, 2019 8:05 am    Post subject: Reply with quote
Datasheet page 29 :
Quote:
In order to read multiple bytes, it is necessary to assert the most significant bit of the sub-
address field. In other words, SUB(7) must be equal to 1 while SUB(6-0) represents the
address of first register to be read.
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snow

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Joined: 28 Jun 2005
Posts: 166
Location: Ashburton / Mid Canterbury / New Zealand
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PostPosted: Mon Aug 05, 2019 9:17 am    Post subject: Reply with quote
Thanks for the reply Smile
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