Steve Karg
ae135cd368
* Added unit test while reading all object properties to flag properties not in the property-list. * Added enumeration for last-property used in unit testing. * Added missing reliability property in the basic multistate output object example. * Removed polarity property in binary value object as it is not standard.
BACnet MS/TP on Arduino Uno R3 Platform - Atmega328p
The Arduino Uno R3 platform for this example uses the following peripherals:
-
USB bootloader using AVR-119 protocol
-
7-position DIP switch for MS/TP MAC address
-
Arduino Uno V3 compatible RS485 shield (DFR0259)
Arduino Uno V3 Pin Mapping
| ATmega328p | Arduino | RS485 DFR0259 | BACnet Object |
|---|---|---|---|
| NC | NC | ||
| +5V | IOREF | ||
| RESET | RESET | RST BUTTON | |
| +3V3 | +3V3 | ||
| +5V | +5V | +5V | |
| GND | GND | GND | |
| GND | GND | GND | |
| VIN | VIN | ||
| ADC0/PC0 | A0 | AV 0 Millivolts | |
| ADC1/PC1 | A1 | AV 1 Millivolts | |
| ADC2/PC2 | A2 | AV 2 Millivolts | |
| ADC3/PC3 | A3 | AV 3 Millivolts | |
| ADC4/PC4 | A4* | ||
| ADC5/PC5 | A5* | ||
| ADC5/PC5 | SCL* | I2C | |
| ADC4/PC4 | SDA* | I2C | |
| AVDD | AREF | ||
| GND | GND | ||
| SCK/PB5 | D13 | LED-L ANODE (+) | BV 99 (output) |
| MISO/PB4 | D12 | BV 9 (output) | |
| MOSI/PB3 | D11 | BV 8 (output) | |
| SS/PB2 | D10 | BV 7 (output) | |
| OC1/PB1 | D9 | BV 6 (output) | |
| ICP/PB0 | D8 | BV 5 (output) | |
| AIN1/PD7 | D7 | BV 4 (input) | |
| AIN0/PD6 | D6 | BV 3 (input) | |
| T1/PD5 | D5 | BV 2 (input) | |
| T0/PD4 | D4 | BV 1 (input) | |
| INT1/PD3 | D3 | BV 0 (input) | |
| INT0/PD2 | D2 | CE DE /RE RTS | RS485 |
| TXD/PD1 | D1/Tx** | TXD | RS485 |
| RXD/PD0 | D0/Rx** | RXD | RS485 |
* ADC4/PC4: A4 and SDA are shared I/O
* ADC5/PC5: A5 and SCL are shared I/O
** shared with Uno R3 USB Tx/Rx. DFR0259 switch ON to disable.
Building this Project
GNU Makefile
There is a GNU Makefile that uses avr-gcc and avr-libc to build the project. avrdude can be used to program the Arduino Uno R3 board via USB.
The GNU Makefile is used in the continuous integration pipeline to validate the build is not broken. The Makefile is called from an Ubuntu image container after installing the necessary tools:
sudo apt-get update -qq
sudo apt-get install -qq build-essential
sudo apt-get install -qq gcc-avr avr-libc binutils-avr avrdude
To add the build and debug tools to MinGW64 environment:
pacman --noconfirm -S mingw-w64-x86_64-gcc-avr
pacman --noconfirm -S mingw-w64-x86_64-avr-libc
pacman --noconfirm -S mingw-w64-x86_64-binutils-avr
pacman --noconfirm -S mingw-w64-x86_64-avrdude
The build sequence is usually:
make clean all
The Makefile includes a recipe to use avrdude to program the Uno R3 via USB
make install
GCC and CStack Usage
CStack check for GCC is included in the device object as property 512. The compile shows 352 (.bss) + 136 (.data) = 488 bytes of RAM used, and the ATmega328 has 2048 bytes of RAM, leaving 1560 bytes for the CStack. BACnet Device object proprietary property 512 is mapped to the CStack Size and returns 1376 using ReadProperty request. After some ReadProperty and WriteProperty requests, the CStack shows 1159 CStack bytes free. Note that the value 0xC5 (197) was used to paint the CStack. Keep this in mind when developing.
Shield option
The DFR0259 shield for RS485 was used, but any RS485 circuit could be attached to the Arduino Uno R3 using the same pins for Tx, Rx, CE RE/DE RTS.
A 7-position DIP switch was connected to GPIO for the MS/TP MAC address, but the value could also be stored in EEPROM.
BACnet Capabilities
The BACnet Capabilities include WhoIs, I-Am, ReadProperty, and WriteProperty support. The BACnet objects include a Device object, 10 Binary Value objects, and 10 Analog Value objects. An GPIO output is controlled by Binary Value object instance 0. All required object properties can be retrieved using ReadProperty. The Present_Value property of the Analog Value and Binary Value objects can be written using WriteProperty. The Object_Identifier, Object_Name, Max_Info_Frames, Max_Master, and baud rate (property 9600) of the Device object can be written using WriteProperty.