The sensor allows for data values of 10 bits but for simplicity I am getting only the 8 bit data
you are using it in 2g mode, so you have only 8bit of data.
The data received when the sensor is on a flat surface is:
this is correct. You have a 8bit range (256 value, from -128 to +128) that map a range from +2g to -2g. So we have 256lsb/4g = 64lsb/g.
Motionless, the lenght of the gravity vector (sqrt(xx+yy+z*z)) must be close to 64. Of corse you need some offset and non-linearity calibration but the data seems fine.
Also if you look at the piece of datasheet you posted in table "Sensitivity", you will see they call the LSB "count", and they are in the range we calculated!
When the self test is run, the results are:
again this is correct, if your sensor is flat in way the Gravity apply on the Z; what you see is the normal gravity (64) summing up to the self-test offset (64), giving you a nice ~128
I adapted to code to get the 10 bits of data:
Why would the 8 bit and 10 bit results return similar values during a self test (around 128)? Should the 10 bit value be 4X greater?
to use 10bit, you must set the full scale range to +-8g. If you look at the piece of datasheet you posted, table "Output Signal", you see how many bit are avaiable for each range.
If you think about it, how does the sensor know if you want to read 8 or 10bit? (remeber the DS say you must read the low register BEFORE high register!) if you read only 8bit, you would be loosing the 2msb, one rapresenting the sign and the other the most important bit that can change your result by 2^9=512
btw also you first 10 bit conversion is wrong as you flip the bit for 2's complement, but does nothing to the value bit.
The solution with bit shitf of 6 follow by divising is working but a bit strange to see. I would go for something more "standard" like
int xData = readRegister (X10_LSB) | (readRegister (X10_MSB) << 8);
if (xData | 0b0000 0010 0000 0000){ //if negative
//keep 9 bit raspresenting the value and multiply by -1 to keep the sign
xData = (xData & 0b0000 0001 1111 1111) * -1;
}
The sensor allows for data values of 10 bits but for simplicity I am getting only the 8 bit data
you are using it in 2g mode, so you have only 8bit of data.
The data received when the sensor is on a flat surface is:
this is correct. You have a 8bit range (256 value, from -128 to +128) that map a range from +2g to -2g. So we have 256lsb/4g = 64lsb/g.
Motionless, the lenght of the gravity vector (sqrt(xx+yy+z*z)) must be close to 64. Of corse you need some offset and non-linearity calibration but the data seems fine.
Also if you look at the piece of datasheet you posted in table "Sensitivity", you will see they call the LSB "count", and they are in the range we calculated!
When the self test is run, the results are:
again this is correct, if your sensor is flat in way the Gravity apply on the Z; what you see is the normal gravity (64) summing up to the self-test offset (64), giving you a nice ~128
I adapted to code to get the 10 bits of data:
Why would the 8 bit and 10 bit results return similar values during a self test (around 128)? Should the 10 bit value be 4X greater?
to use 10bit, you must set the full scale range to +-8g. If you look at the piece of datasheet you posted, table "Output Signal", you see how many bit are avaiable for each range.
If you think about it, how does the sensor know if you want to read 8 or 10bit? (remeber the DS say you must read the low register BEFORE high register!) if you read only 8bit, you would be loosing the 2msb, one rapresenting the sign and the other the most important bit that can change your result by 2^9=512
btw also you first 10 bit conversion is wrong as you flip the bit for 2's complement, but does nothing to the value bit.
The solution with bit shitf of 6 follow by divising is working but a bit strange to see. I would go for something more "standard" like
int xData = readRegister (X10_LSB) | (readRegister (X10_MSB) << 8);
if (xData | 0b0000 0010 0000 0000){ //if negative
//keep 9 bit raspresenting the value and multiply by -1 to keep the sign
xData = (xData & 0b0000 0001 1111 1111) * -1;
}
The sensor allows for data values of 10 bits but for simplicity I am getting only the 8 bit data
you are using it in 2g mode, so you have only 8bit of data.
The data received when the sensor is on a flat surface is:
this is correct. You have a 8bit range (256 value, from -128 to +128) that map a range from +2g to -2g. So we have 256lsb/4g = 64lsb/g.
Motionless, the lenght of the gravity vector (sqrt(xx+yy+z*z)) must be close to 64. Of corse you need some offset and non-linearity calibration but the data seems fine.
Also if you look at the piece of datasheet you posted in table "Sensitivity", you will see they call the LSB "count", and they are in the range we calculated!
When the self test is run, the results are:
again this is correct, if your sensor is flat in way the Gravity apply on the Z; what you see is the normal gravity (64) summing up to the self-test offset (64), giving you a nice ~128
I adapted to code to get the 10 bits of data:
Why would the 8 bit and 10 bit results return similar values during a self test (around 128)? Should the 10 bit value be 4X greater?
to use 10bit, you must set the full scale range to +-8g. If you look at the piece of datasheet you posted, table "Output Signal", you see how many bit are avaiable for each range.
If you think about it, how does the sensor know if you want to read 8 or 10bit? (remeber the DS say you must read the low register BEFORE high register!) if you read only 8bit, you would be loosing the 2msb, one rapresenting the sign and the other the most important bit that can change your result by 2^9=512
btw also you first 10 bit conversion is wrong as you flip the bit for 2's complement, but does nothing to the value bit.
The solution with bit shitf of 6 follow by divising is working but a bit strange to see. I would go for something more "standard" like
int xData = readRegister (X10_LSB) | (readRegister (X10_MSB) << 8);
if (xData | 0b0000 0010 0000 0000){ //if negative
//keep 9 bit raspresenting the value and multiply by -1 to keep the sign
xData = (xData & 0b0000 0001 1111 1111) * -1;
}
The sensor allows for data values of 10 bits but for simplicity I am getting only the 8 bit data
you are using it in 2g mode, so you have only 8bit of data.
The data received when the sensor is on a flat surface is:
this is correct. You have a 8bit range (256 value, from -128 to +128) that map a range from +2g to -2g. So we have 256lsb/4g = 64lsb/g.
Motionless, the lenght of the gravity vector (sqrt(xx+yy+z*z)) must be close to 64. Of corse you need some offset and non-linearity calibration but the data seems fine.
Also if you look at the piece of datasheet you posted in table "Sensitivity", you will see they call the LSB "count", and they are in the range we calculated!
When the self test is run, the results are:
again this is correct, if your sensor is flat in way the Gravity apply on the Z; what you see is the normal gravity (64) summing up to the self-test offset (64), giving you a nice ~128
I adapted to code to get the 10 bits of data:
Why would the 8 bit and 10 bit results return similar values during a self test (around 128)? Should the 10 bit value be 4X greater?
to use 10bit, you must set the full scale range to +-8g. If you look at the piece of datasheet you posted, table "Output Signal", you see how many bit are avaiable for each range.
If you think about it, how does the sensor know if you want to read 8 or 10bit? (remeber the DS say you must read the low register BEFORE high register!) if you read only 8bit, you would be loosing the 2msb, one rapresenting the sign and the other the most important bit that can change your result by 2^9=512
btw also you first 10 bit conversion is wrong as you flip the bit for 2's complement, but does nothing to the value bit.
The solution with bit shitf of 6 follow by divising is working but a bit strange to see. I would go for something more "standard" like
int xData = readRegister (X10_LSB) | (readRegister (X10_MSB) << 8);
if (xData | 0b0000 0010 0000 0000){ //if negative
//keep 9 bit raspresenting the value and multiply by -1 to keep the sign
xData = (xData & 0b0000 0001 1111 1111) * -1;
}