Embedded Software is written for LPC1549 development board.
Primary language is C++.
The project creates a smart system solution for adjusting and monitoring pressure in ventilation, using ABB frequency controller simulator.
General description of the project is provided in root folder.
The system consists of several components:
- ABB Frequency Controller simulator (Arduino)
- Ventilation and servo, controlled by ABB drive.
- LiquidCrystal display
- Button module with 3 buttons
- Wi-Fi module
The main idea is to provide two operation modes for the system: automatic and manual:
- In manual mode frequency is controlled by the user, other items must not be adjustable.
- In automatic mode system's target prussere is controlled by the user, other items must not be adjustable.
The system expects input from WEB UI (via MQTT payload) and Button module.
Considering several input and output methods, software needs to syncronize LCD, WEB UI with current machine's state.
In order for device to establish connection with web, under project_main/includes/project_main.h specify values of:
NETWORK_SSID, NETWORK_PASS, MQTT_IP, MQTT_PORT.
If you would like to use device with no MQTT connection, define NO_MQTT as 1.
The Liquid Crystal Display shows a simple menu with four items:
- Mode (Automatic / Manual) -> adjust this value to change the mode
- Frequency (0 / 100) -> Adjust this value to change speed of the fan
- Target pressure (0 / 120) -> Adjust this value to change setpoint in automatic mode
- Pressure (0 / 100) -> Display current system's pressure
The system can be controlled with the buttons:
- Left button -> move left / decrement value
- Middle button -> select element / increment value
- Right button -> move right / increment value
Note, that in automatic mode frequency cannot be incremented/decremented.
As well as in manual mode, target pressure is not adjustable.
Menu item "Pressure" cannot be adjusted at any points.
The following diagram describes the hardware architecure, that includes the components described above, in the abstract form.
More detailed information is provided further in schematics.
MCU LPC1549: MCU
LCD: Not specified, containg backlight
WI-Fi module: Not specified, PCB provided by Metropolia UAS
Pressure Sensor SDP6x0-125: SDP
ABB Frequency Simulator: ABB
Abstract software architecture is described in the figure below.
As we can see, the main components of the architecture are:
- State Machine
- MQTT payloads
- Menu button inputs
- Liquid Crystal Display output
- Main Program body
In addition to interaction described in a diagram, main program generate eTick event for state machine at 1T rate.
Colors on the diagram describe when interaction is happening.
Purple - interaction happens immediately
Black - interaction happens periodically (specified by label).
1T = 1 Tick = 1000 ms.
Some of the complex concepts are described in details.
State machine architecture is described in the UML, introduced in this section.
Member variables of state machine:
Pressure, Setpoint, Frequency, Mode, Timer, Status, Pointer to ABB drive, Pointer to SDP pressure sensor
Statuses:
0 - status OK
1 - status LOADING (unused in current implementation)
-1 - status HARDWARE_FAILURE
-2 - status TIMEOUT (setpoint unreachable)
The functions introduced in the UML are the member dunctions of state machine.
Additionally, there should be a member function for exporting data and status (returning members).
- read_pressure - read from SDP
- set_frequency(v) - set frequency to v
- adjust_frequency - automatically adjust frequency for a specific step
- modbus_heartbeat - keep modbus connection awake
The described is recommended and current implementation. Differences and improvements are possible.
The idea behind main handlers is to have a "connector" that will keep WEB UI, LCD and State machine syncronized.
In order to achieve this syncronization, handler functions are called with periodicity described in the software acrhitecture diagram.
There are four handlers that follow the same pattern:
pressure_handler, frequency_handler, setpoint_handler, mode_handler
General algorithms for handlers:
handler(value):
- If LCD_CURRENT != value, then update LCD
- If STATE_MACHINE_CURRENT != value, then update STATE_MACHINE
One external library was used for JSON parsing.
Credits: JSON
The program expects JSON string over MQTT, containing setpoint, speed and mode with integer values:
{ "setpoint": ..., "speed": ..., "mode": ... }