TMAG3001: Calculating single axis BOP and BRP

larry fischer

Part Number: TMAG3001

Tool/software:

Hi,

Im still working on my previous issue - getting the TMAG3001 to trigger once when a button is pushed and released. Its not obvious to me how to calculate the BOP and BRP values. My current mode is Z axis. Parameters are below. I can make it trigger continuously while pushed, but not just once per press. Raw values range from ~13000 when unpressed to ~25000 when pressed.

temp 24.31
X 0.00 Raw 0
Y 0.00 Raw 0
Z 29.52 Raw 12400
angle 0.00
Mag 00.00
Status 10
Press count: 62897
Int Config1 0x14
SensorConfig1 0x40
SensorConfig2 0x1
SensorConfig3 0x20
SensorConfig6 0x7F
Thr Config1 0x0
Thr Config2 0x0
Thr Config3 0x50

2 months ago

+1 Alicia Rosenberger 2 months ago

TI__Genius 13640 points

Hi Larry,

Thank you for posting to the Sensors forum!

BOP gets set in the THR_CONFIG_x registers as an 8-bit signed magnitude value for unipolar switch mode (7-bit unsigned for omnipolar switch mode).

To calculate the BOP value from mT, the Equation 13 from the datasheet can be used:

From the above, solving for Threshold (mT) you get the following equation:

SENS, depending on your range the options would be:

for the A1 variant

for the A2 variant

For unipolar switch mode, if setting a negative threshold, the most significant bit should be set to 1.

To set BRP when THR_SEL = 2h, see the THR_HYST bits in Device_Config_2. BRP values when in switch mode are represented in 12-bit resolution, so to convert to a mT value, the THR_HYST value will need to be converted to 16-bit resolution.

For example, if THR_HYST is set to 2h, the BRP would be 8LSB of threshold in 12-bit resolution. To convert to a mT value, please see the below example:

Convert 8LSB from 12-bit resolution to 16-bit resolution by bit shifting 8LSB to the left 4-bits
1. 8LSB << 4 = 128LSB
Convert LSB to mT, assuming that the magnetic range is ±40mT SENS will be 885LSB/mT
1. 128LSB / 885LSB/mT ≈ 0.145mT

Best,

~Alicia