Hardware layout and configuration
UM1537
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Doc ID 023059 Rev 1
The RS-485 communication is supported by the RS-485 transceiver ST485ABDR, which is
connected to pin4 and pin9 of the D-type 9-pin connectors CN7 (that share the same
connector as USART1).
2.8 Linear
sensor
The linear sensor is supported on the STM320518-EVAL evaluation board and connected to
four capacitive sensing channels (PB[11:14]) in group6 with an active shield connected to
two capacitive sensing channels (PC5 and PB0) in group3.
Note:
The linear sensor is only fully functional when the STM320518-EVAL is powered on power
mode 1 (both VDD and VDDA are connected to a fixed 3.3 V). It is potentially necessary to
adjust the capacitor value of C14 and C15 and the firmware to adapt them to the voltage
range from 2 V to 3.6 V of VDD on power modes 2 and 3.
2.9 MicroSD
card
The 2 GB (or more) MicroSD card connected to the SPI1 port of the STM32F051R8T6 is
available on the board. MicroSD card detection is managed by the standard IO port PB15.
2.10 Analog
input
The two-pin header CN8 and 10 kohm potentiometer RV3 are connected to PC1 of the
STM32F051R8T6 as an analog input. A low-pass filter can be implemented by replacing
R60 and C36 with the correct resistor and capacitor values as required by the end-user
application.
2.11
LDR (light dependent resistor)
The VDDA is divided by the resistor bridge of the LDR VT9ON1 and 8.2 K resistor. It is
connected to PA1 (/ADC IN1) as shown in
.
Table 11.
RS-485 related solder bridges
Jumper
Description
SB11,SB12
The external failsafe biasing are enabled when solder bridges SB11 and SB12 are
closed.
Default setting: not fitted
SB8
The bus termination is enabled when solder bridge SB8 is closed.
Default setting: not fitted
SB16
The AC termination is disabled when solder bridge SB16 is closed for high baud rate
communication.
Default setting: not fitted
