Start Up
1. Set Up Microcontroller Registers
2. Calibrate Measurements
A: Number of Collected Samples < 32
B: Push-Button Pressed
C: 32 Samples Collected
Collect A2
Samples
Collect A3
Samples
B
A
A
A
A
B
B
B
Display Measurement
and Check Measurement Mode
C
C
C
C
Collect A1
Samples
Collect A4
Samples
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SLYU047A – April 2018 – Revised May 2018
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Copyright © 2018, Texas Instruments Incorporated
DRV5055EVM
3
Hardware
The DRV5055 is a linear Hall effect magnetic-sense solution that provides ease of use and high
performance. The DRV5055EVM is intended to provide basic functional evaluation of this device family.
The fixture layout is not intended to be a model for the target circuit, nor is it laid out for electromagnetic
compatibility (EMC) testing. The DRV5055EVM consists of one PCB with each of the gain variants of the
DRV5055. The EVM kit also provides a USB cable for quick power-up, as well as a magnet for quick
qualitative assessment of the DRV5055 variants performance.
3.1
Features
The layout of the DRV5055EVM printed circuit board (PCB) is designed to provide the following features:
•
Evaluation of all gain options for the DRV5055
•
Easily access device pins through test points
•
Easily read voltage, mT, and microcontroller ADC memory values from the onboard LCD
•
Toggle between devices with a press of the
Device Select Switch
, push-button S1.
See the links in
Table 3
for comprehensive information about the DRV5055 family of devices.
3.2
Theory of Operation
The DRV5055EVM is a plug and play board, requiring only that the user supply power and provide a
magnetic stimulus after the initial calibration. The ease of operation can be attributed to the onboard
microcontroller. The source code for the microcontroller is available on the DRV5055 web folder under
Tools and Software
. The basic operation of the microcontroller source code is outlined in the state
machine diagram shown in
Figure 1
. Upon receiving power, the microcontroller registers are set up to
properly interact with the other devices on the board. Then, a preliminary measurement of each DRV5055
gain variant is taken. It is imperative that the magnetic stimulus of interest is not present at this time, as
this measurement sets the 0 point in the mT measurement display. After calibration is complete, the LED
for the DRV5055A1 powers on by default. At this point, the EVM microcontroller begins continuously
sampling the DRV5055A1. Pressing push-button S1 results in the EVM sampling the next adjacent device.
After every 32 samples are taken, the device calculates an average, and processes the data to fit the
format selected by the slider switch K1.
Figure 1. Microcontroller Source Code Operation