Starting from left to right in Figure 4-5:
- WAKE: The wake widget
controls the nSleep device which directly controls the nSleep pin. The user
cannot switch between modes when the device is asleep in SPI mode, and the
default for the SPI variant is awake.
- ENABLE DRIVER: Directly
controls the DRVOFF pin. When the bridge control is active, the user cannot
change between modes or observe the passive diagnostics.
- MODE: Programs the S_MODE
register and alters the appearance of the BRIDGE CONTROL depending on
your selection. There is a difference in MODE options between the DRV824x
and DRV814x device families. The DRV814x devices only operate in one fixed mode
where the user can only switch between high side and low side load connections.
The high side connection connects the load between VM and OUT while the low side
connection connects the load between OUT and GND as can be seen in Figure 4-6.
In the DRV824x devices,
Phase/Enable mode only has one duty cycle slider while the Independent
Half-bridge mode and PWM mode each have two sliders.
When changing between modes,
there is a Load Connection Warning popup. If the load is incorrectly
connected and the user attempts to run the motor on the GUI, then the load
can damage the device and cause harm to the user. This is especially
important when in Independent Half-Bridge mode. The load connection warning
appears every time the user selects a new mode or repeatedly selects the
current mode. Figure 4-7 shows the pop-up window for the Independent Half-Brige mode
selection.
Note: With the
DRV824x devices, the GUI allows to switch between high side and low side
load connection only using the Independent Half-Bridge mode selection
pop-up window.
Note: DRV824x-Q1EVMs with
HVSSOP package driver device has OUT1 and OUT2 silk screen labels
interchanged.
- BRIDGE CONTROL The Start
Drive button allows the software state machine to start running on the MCU.
Prior to starting, the user can tweak the desired direction, ramp rate, slew
rate, and check for properly connected load connections. After pressing
,
the duty cycle sliders become available for modification. The output
automatically soft-starts using the Ramp Rate parameter.
- PASSIVE/ACTIVE DIAGNOSTICS
The SPI variant features both passive and active diagnostics. The passive
diagnostics also known as Off-line Passive (OLP), can only be used when
ENABLE DRIVER is disabled (Off-state). OLP shows up in a separate
pop-up window as can be seen in Figure 4-8. A representative table from the device data sheet is displayed in this
window for guidance to perform the passive diagnostics. Each row of the table
covers a specific combination of user input selection, the corresponding OLP
setup and load status inference from the OLP_CMP comparator output on the nFAULT
pin. See the device data sheet for more details. The required S_DIAG selection
can be made using the GUI for SPI devices. The required DIAG jumper setting must
be done when WAKE is Asleep for HW devices prior to enabling passive
diagnostics. The nSLEEP and DRVOFF inputs are logic 1 while observing passive
diagnostics. Inputs for EN/IN1 and PH/IN2 are selected using the switches in the
GUI. The pull up can take a few seconds, pull down resistors, and the OLP_CMP
output status to update due to the latency between the EVM hardware and the GUI
application.The Active Open Load Diagnostics are only for High-Side loads with the
DRV824x device, Independent Half-Bridge mode, and the DRV814x Half-Bridge
device. The Active Diagnostics not exist in the Hardware variants.
- FAULTS Press the clear
button to clear all the latched faults. Next to the clear button is the
CONFIG button for SPI variants. This button allows the user to have
more control over the modification of fault reporting. For example, selecting
Automatic Retry allows the faults to clear without any manual
interference.
- BRIDGE CURRENT The Bridge
Current displays moving average and cycle peak load current values calculated
from a window of samples of the voltage VIPROPI (VIPROPI =
RIPROPI × IPROPI) on the IPROPI output. Each periodic window of
samples is referred to as a cycle. The samples are captured using the integrated
10-bit analog to digital converter in the MCU of the EVM. The displayed values
are only indicative of the load current during the sampling window. The IPROPI
analog output pin available on the header J4 of the EVM can be used for accurate
real-time measurement using a multimeter or for capturing the load current
waveform using an oscilloscope. Current scaling is done by selecting a desired
RIPROPI resistor with the IPROPI jumper setting on the current
limit header J2 of EVM. See Section 2.2.5. Match the
RIPROPI setting on the GUI with the IPROPI jumper setting of the
EVM.
Note: A possibility is that the bridge current can
show a value of 10’s of mA for the moving average and cycle peak display in the GUI
even with no motor connected while the bridge is enabled and the PWM output set with
a non-zero duty cycle value. This is due to the offset in the microcontroller ADC
measurement EVM. For accurate current reading, TI recommends using the IPROPI analog
output on the header J4 to be measured externally. The voltage on this pin is
dependent on the RIPROPI selection and the load current. The IPROPI current scaling
factor for the driver device can be found in the data sheet.
Every control also has a help tip associated to
quickly help the user while running the GUI.