IoD Display Module Series IoD-09TH/SM
©
2017 4D SYSTEMS Page 8 of 22 www.4dsystems.com.au
Hardware Interface - Pins
This section describes in detail the hardware interface
pins of the device.
Serial Port
–
TTL Level Serial
The ESP8266
Processor has a hardware asynchronous
serial ports that can be accessed via the headers on
the IoD-09 module. The serial port can be used to
communicate with external serial devices.
The primary features are:
•
Full-Duplex 8 bit data transmission and reception.
•
Data format: 8 bits, No Parity, 1 Stop bit.
•
Independent Baud rates from 300 baud up to
921600 baud.
•
Single byte transmits and receives or a fully
buffered service. The buffered service feature
runs in the background capturing and buffering
serial data without the user application having to
constantly poll any of the serial ports. This frees
up the application to service other tasks.
A single byte serial transmission consists of the start
bit, 8-bits of data followed by the stop bit. The start bit
is always 0, while a stop bit is always 1. The LSB (Least
Significant Bit, Bit 0) is sent out first following the start
bit. Figure below shows a single byte transmission
timing diagram.
The serial port is also the primary interface for User
program downloads, and configuration via the IDE.
System Pins
+5V (Module Voltage Input)
Module supply voltage input pins. This pin should be
connected to a stable supply voltage in the range of
4.0 Volts to 5.5 Volts DC. Nominal operating voltage is
5.0 Volts. Note backlight brightness will be dimmer for
voltages under 5.0V.
GND (Module Ground)
Device ground pins. Both pins should be connected to
ground.
RESET (Module Master Reset)
Module Master Reset pin. An active low pulse of
greater than 2μs will reset the module. Internally
pulled up to 3.3V via a 10K resistor. Only use open
collector type circuits to reset the device if an external
reset is required.
GPIO0 (Flash Programming)
This pin is primarily used for the Flashing of the
ESP8266’s Flash Memory via the programming
software. This pin must be left floating at power-up to
enable the ESP8266 to boot correctly. Once the
module has booted, this pin is freely available to be
used for I2C or GPIO operations.
GPIO2 (Flash Mode)
This pin is primarily used to tell the ESP8266 which
mode it needs to be in, and to load from Flash
Memory. This pin must be left floating at power-up to
enable the ESP8266 to boot correctly. Once the
module has booted, this pin is freely available to be
used for I2C or GPIO operations.
GPIO12 (MISO)
This pin is the MISO SPI pin, which is used for the
Display, the microSD card, and is also available for the
User to connection additional SPI devices to the bus. It
is used in conjunction with the other SPI pins, and
requires GPIO0, GPIO2 or GPIO16 for the Chip Select
for any additional devices.
GPIO13 (MOSI)
This pin is the MOSI SPI pin, which is used for the
Display, the microSD card, and is also available for the
User to connection additional SPI devices to the bus. It
is used in conjunction with the other SPI pins, and
requires GPIO0, GPIO2 or GPIO16 for the Chip Select
for any additional devices.
GPIO14 (SCK)
This pin is the SCK SPI pin, which is used for the Display,
the microSD card, and is also available for the User to
connection additional SPI devices to the bus. It is used
in conjunction with the other SPI pins, and requires
