The LCD-TFT controller interface with dual-layer support takes advantage of the Chrom
‑
ART Accelerator. This
graphics accelerator creates content twice as fast as the core alone and features 2-D raw data copy, image format
conversion and image blending.
1.6
Digital inputs and outputs
The 12 digital inputs are arranged in groups of 8 and 4 channels. On the terminal block, they marked as I0 with 8
channels and provide 8 high side inputs to
. Each channel is marked as I0.x (i.e. from I0.0 to I0.7).
Four high/low inputs for the two
are accessible in the terminal block I1 (channels I1.0 to I1.3).
The 12 digital outputs are grouped similarly in two terminal blocks. 8 channels from
on the terminal block, while 4 low side outputs from
are in the terminal block Q1.
Input and output terminals are placed symmetrically.
1.7
Power distribution on the board
The
evaluation board is designed to work with 24 V nominal power supply. The MCU and
logic circuit are galvanically isolated from the field side circuit.
P-Channel MOSFET is crucial for the reverse polarity protection circuit ensuring low voltage drop
and high current capability in addition to quick response time. The board also provides suitable surge protection
and noise filtering.
Figure 6.
Power and logic connections
ISO8200AQ
3.3 V
5 V
5V_CLT01
LDK220M3R
CLT01-
38SQ7
isolator
24 V
STL42P6LLF6
PMOS for
Reverse Voltage
Protection
DC-DC
converter
(24V to 5V)
STM32F746
MCU
IP4260L
16 V
STLD40DPUR
(backlight LED
driver)
RAM
3.5” LCD +
Touch
Screen
5 V
3.3 V
3.3 V
3.3 V
GPIO
SPI
LM7805
24 V
GPIO_OUT
SPI
opto
CLT03-2Q3
(self-powered)
CLT03-2Q3
(self-powered)
isolator
Field-side
device
Logic device
opto
FAULT_CH to MCU
USART_Tx
USART_Rx
MCU_Rx
MCU_Tx
FLASH
(demo mode)
USB MICRO-AB`
non-isolated
24 V
5V_field
5 V
3.3 V
16 V
Logic:
opto
opto
SPI
5V_field
24 V
External logic
supply
24 V
5V Input
24 V
24 V
Field:
5V_CLT01 5V_field
opto
is a boost converter (5 V supply to ~18 V) needed for the LCD back-light. The converter is a pulse
frequency modulation (PFM) inductor switch that can work in discontinuous mode (DCM). A minimum OFF time of
the embedded TSW boost switch is fixed internally and allows limiting the switching frequency. The output current
capability is 20 mA with an output voltage of 37 V (maximum rating). The regulation is done by sensing the LED
current through a current resistor (R86). The device can be turned ON/OFF through the logic enable signal pin
(EN). A low frequency PWM signal is used to dim the LCD back-light.
1.8
MCU interfaces and pin allocation
The SPI-2 interface is shared between
with separate chip-select lines from the
are interfaced through GPIO pins.
The
fault indications are interfaced with the MCU through dedicated GPIO inputs. Two
debug LEDs (D36, D39) are controlled through GPIO output.
The TFT display is connected through dedicated pins in RGB16 mode. i2C4 is used to interface the touch sensor
with the display. The touchscreen resolution is 800x480 while LCD screen resolution is 320x240. Thus, scaling is
applied to find the touch corresponding to the point on the LCD.
UM2933
Digital inputs and outputs
UM2933
-
Rev 1
page 9/42
