ConnDuino quick reference

This is the page, where the functionality of ConnDuino pins and jumpers is shortly described.

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Functionality of the "Arduino Uno compatible digital pins" of ConnDuino

Digital pin Primary function (Arduino compatible) Secondary function (Connduino specific) Comments

0

Digital I/O, reserved for serial data receive

None

Connected to the TX pin of the FTDI header

1

Digital I/O, reserved for serial data transmit

None

Connected to the RX pin of the FTDI header

2

Digital I/O

Interrupt from an installed RTC module (i.e. alarm function)

If the jumper headers “INTR@D2” are bridged (near the RTC pins) the D2 is connected with the SQW gate of the RTC, which may send the interrupt signal. Otherwise, D2 is free for use.

3

Digital I/O with PWM

TFT backlight control

If the “TFT DIM” jumper headers are bridged, D3 is connected to the LED pin of the TFT header. The backlight led(s) may be controlled by setting the PWM level.

4

Digital I/O

Data to (or from) an installed RF module

Connected to the data pin, named "@D4", of the RF module header, (normally 433MHZ, ACK modulation). A transmitter or receiver may be installed. 

5

Digital I/O with PWM

None

 

6

Digital I/O with PWM

Slave Select for an installed SPI device.

Connected to the pin SS2 of the SPI pin headers.

7

Digital I/O

Slave Select for an installed SPI device.

Connected to the pin SS1 of the SPI pin headers

8

Digital I/O

Slave Select for an installed TFT (in SPI mode)

Connected to the CS pin of the TFT pin header. TFTs drived by the ILI9341 chip have been tested. 

9

Digital I/O with PWM

Reset for an installed TFT (in SPI mode)

Connected to the RST pin of the TFT pin header. TFTs drived by the ILI9341 chip have been tested. 

10

Digital I/O with PWM

Data/Command control for an installed TFT (in SPI mode)

Connected to the DC pin of the TFT pin header. TFTs drived by the ILI9341 chip have been tested. 

11

Digital I/O with PWM

SPI bus MOSI

(Master Out-Slave In)

Connected to all SPI MOSI pins on board (including TFT).  

12

Digital I/O

SPI bus MISO

(Master In-Slave Out)

Connected to all SPI MISO pins on board (excluding TFT).  

13

Digital I/O

SPI bus SCK

(Serial Clock)

Connected to all SPI SCK pins on board  (including TFT).  

 

Functionality of the "Arduino Uno compatible analog pins" of ConnDuino
Digital pin Primary function (Arduino compatible) Secondary function (Connduino specific) Comments

0

Analog input or digital I/O

One wire interface

Connected to the board temperature sensor (Dallas 18B20), while pulled up to VCC through a pull-up resistor (4K7 suggested).

1

Analog input or digital I/O

None

 

2

Analog input or digital I/O

None

If the jumper headers “INTR@D2” are bridged (near the RTC pins), D2 is connected with the SQW gate of the RTC, which may send the interrupt signal. Otherwise, D2 is free for any use.

3

Analog input or digital I/O

Analog input from the buttons

Connected to the voltage ladder in the buttons region, only if the nearby solder pads (at the backside) are shorted. Otherwise it works as normal analog pin.

4

Analog input or digital I/O, reserved for the I2C interface SDA line.

None  

Connected to every existing SDA pin on board (EEPROM, RTC, LCD header, SDA pins). The pull up resistor R7, if installed, pulls the line voltage to the either 3.3v or 5v depending on the I2C_VSEL jumper header setting.  

5

Analog input or digital I/O, reserved for the I2C interface SCL line.

None  

Connected to every existing SCL pin on board (EEPROM, RTC, LCD header, SCL pins). The pull up resistor R6, if installed, pulls the line voltage to the either 3.3v or 5v depending on the I2C_VSEL jumper header setting.  

 

Functionality of the ConnDuino TFT pins
Pin Comments

+3v3

To positive 3.3V supply.

GND

To ground.

CS

Chip Select (SPI signal). Wired to digital pin 8 through the gates 11-12 of the CD4050 chip or the respective backside solder pads, if bridged.

RST

Reset. Wired to digital pin 9 through the gates 9-10 of the CD4050 chip or the respective backside solder pads, if bridged.

DC

Data/Command control. Wired to digital pin 10 through the gates 6-7 of the CD4050 chip or the respective backside solder pads, if bridged.

MOSI

Master Out-Slave In (SPI signal). Wired to digital pin 11 through gates 4-5 of the CD4050 chip or the respective backside solder pads.

SCK

Serial Clock (SPI signal). Wired to digital pin 13 through the gates 14-15 of the CD4050 chip or the respective backside solder pads, if bridged.

LED

Backlight control. If the “TFTDIM” jumper header is shorted, this pin is directly connected to the 3.3V supply. If not, the pin is connected to the digital pin 3, from which the backlight intensity may be adjusted using PWM.

NC

Not connected. This pin is normally called MISO in the TFT board. Such a signal is not occurring by a TFT screen. Furthermore, it runs in the opposite direction (from the device towards the microcontroller) and interfacing it through the CD4050 chip is impossible. So, it is not connected to any other pin on the ConnDuino board.

 

Functionality of the ConnDuino LCD (I2C) pins
Pin Comments

GND

To ground.

+5v

To positive 5V supply. Not affected by the  “VCC-SEL” jumper header.

SDA

I2C serial data line.

SCL

I2C serial clock line.

 

Functionality of the ConnDuino RF433 pins
Pin Comments

GND

To ground.

+5v

To positive 5V supply. Not affected by the  “VCC-SEL” jumper header.

@D4

Data send or receive. Connected to the digital pin 4.  

 

 

Functionality of the ConnDuino RTC (I2C) pins
Pin Comments

GND

To ground.

Vcc

To positive voltage (either 5V or 3.3V, same to the microcontroller voltage). The DS3231 chip has a range of 2.3V~5.5V supply.

SDA

To I2C SDA bus (i.e. analog pin 4).

SCL

To I2C SCL bus (i.e. analog pin 5).

SQW

This pin outputs the interrupt signals from the rtc or alternatively a square-wave signal. If the nearby INTR jumper header is shorted, the signal reaches digital pin #2, which is one of the two Arduino Uno pins, capable to handle interrupts.

32K

This pin outputs the oscillator signal from the rtc chip. The DS3231 chip integrates a 32KHz crystal. This signal is not mapped to any of the Arduino pins, but instead a nearby duplicated 32K header is provided, in order to forward it anywhere, if need be.

 

ConnDuino jumper headers
Jumper Comments

VCC-SEL

Selects the voltage supplied to the microcontroller and other devices. Settings are for 5V or 3.3V.

I2C-SEL

Selects the voltage supplied to the I2C interface lines SDA and SCL. Settings are for 5V or 3.3V.

TFT-DIM

Controls the backlight of the TFT module. If shorted the TFT LED pin is directly connected to 3.3V supply. If not, the pin is connected to the digital pin 3, from which the backlight intensity may be adjusted using PWM.

INTR

If shorted, the SQW pin of the RTC connects to the digital pin #2, which maps to one of the two Atmega328 pins, capable to handle interrupts.

 

Capacitor Values
Name Value Device Type
C1 1 uF smd 0805 / ceramic
C2 47 uF through hole / electrolytic 
C3 47 uF through hole / electrolytic
C4 100 nF smd 0805 / ceramic
C5 22 pF smd 0805 / ceramic
C6 22 pF smd 0805 / ceramic
C7 100 nF smd 0805 / ceramic
C8 100 nF smd 0805 / ceramic

 

Resistor Values
Name Value Device Type
R1 1K smd 0805
R2 10K smd 0805
R3 1M smd 0805
R4 4K7 smd 0805
R5 1K smd 0805
R6 5K smd 0805
R7 5K smd 0805
R8 50 Ω smd 1206
R9 1K smd 0805
R10 1K smd 0805
R11 1~5K smd 0805
 

See also

Additional information regarding the ConnDuino board design and functionality can be found in the following articles:

An introduction to ConnDuino

The Arduino in ConnDuino

ConnDuino power supply

ConnDuino interfaces to add-on modules

Expanding ConnDuino: push buttons and breadboard

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