2. SAAT Corporation
Your Home Environment Monitoring System 1
Contents
What is it?…………………………………………………………………………….. 2
In the box …………………………………………………………………………….. 2
Features …………………………………………………………………………….. 2
Top Level Design ……………………………………………………………………. 3
Modular Software ……………………………………………………………………. 4
Local Operation Mode FSM …………………………………………………… 5
Remote Operation Mode FSM …………………………………………………… 8
Keypad …………………………………………………………………………….. 11
EAR DOG Module LCD ……………………………………………………………. 13
Honeywell HumidIcon Temperature and Humidity Sensor …………………. 14
Pressure Sensor …………………………………………………………………….. 16
MAX1270 AnalogtoDigital Converter …………………………………………… 17
XBee Wireless Module ……………………………………………………………. 19
Troubleshooting …………………………………………………………………….. 21
Contact Information ……………………………………………………………. 21
3. SAAT Corporation
Your Home Environment Monitoring System 2
Welcome to your SAAT system
What is it?
This system is an Environmental Monitoring and Control System (EMCS) that can
monitor the temperature, humidity and pressure of the room as well as adjust the temperature
and humidity to a set level. Our system has two different operation modes: local mode and
remote mode. In local mode, the measurands can be displayed on an LCD screen built into the
system and the setpoints for temperature and humidity can be modified using the keypad. In
remote mode, the same operations can be executed over the internet remotely from any internet
capable device. This is the biggest advantage of the system.
In the box
● Environmental Monitoring and Control System (EMCS) unit
● Power adapter (9V output)
● Control signals connector for AC, Furnace, Humidifier and Dehumidifier
Features
● Read the temperature
● Read the humidity
● Read the pressure
● Set the temperature to control the AC or Furnace
● Set the humidity to control the humidifier or dehumidifier
● Inbuilt wifi unit to perform all operations remotely from any internet connected device
● Optional 9V battery connector for ease of use
4. SAAT Corporation
Your Home Environment Monitoring System 3
Top Level Design
The following are the components of the system:
EA DOGM163A LCD controller and driver
Honeywell HumidIcon Digital Temperature and Humidity Sensor
MPXHZ6130A Pressure Sensor
MAX1270 AnalogtoDigital Converter with SPI
4x4 Keypad (Some keys are not used for the final design)
XBee Wireless Module
Control signals for AC, Furnace, Humidifier and Dehumidifier
Figure 1: Top level system block diagram
The system uses SPI to communicate with the sensors and the LCD display. RS232
communication protocol is used to send and receive data via the wireless module. The AVR240
design is used for the keypad interface to minimize hardware requirements. The system uses
two separate finite state machines for local operation mode and remote operation mode. Both
the state machines are described in detail below. The schematic of the ATmega128 is attached
in the Appendix.
5. SAAT Corporation
Your Home Environment Monitoring System 4
Modular Software
Figure 2: Modular Program Interaction
The functionality of the EMCS built upon several modules of code that divide and group the tasks
carried out by the system into manageable building blocks. The figure above depicts the primary
functions the EMCS undertakes:
● Background Tasks involve measuring the current temperature, humidity, and
pressure, and displaying them to the LCD. The measured values are also
compared against the set point values set by the user to determine if system
needs to turn on or off the AC, furnace, humidifier, and/or dehumidifier.
● Finite State Machines EMCS switches between two FSM depending on which
mode the EMCS is currently operation in. Each mode is designed to expose the
user to different I/O capabilities of the EMCS. Thus improving the versatility of
system
● Interrupt Driven the interrupt service routines allow for the handling of I/O from
the user through their use of the keypad, or a terminal when the EMCS is wireless
mode.
The remote_op_emcs.c located in the appendix us driver program for the EMCS. The
program interacts with the modules max1720.c and baro_pressure.c to communicate with the
MAX1270 to retrieve the barometric pressure. The program interacts with humidicon_task2 and
temp_humid_humidicon to communicate with the Humidicon to retrieve both temperature and
relative humidity. The program is able to display characters on the LCD due to the interaction to
lcd_etc. and log_dog_iar_driver.asm The USART2.c contains the ISR (interrupt service routine)
which stores received characters in the receive buffer, and transmits characters in the transmit
buffer out.
6. SAAT Corporation
Your Home Environment Monitoring System 5
Local Operation Mode FSM
This Finite State Machine implements the operations of the EMCS in Local operation
mode. The keypad is used for user input and the LCD display is used for output. This system
allows the user to change the setpoints for the temperature (ST) and the humidity (SH). The
setpoints can be modified one of two ways; by pressing the up or down keys on the keypad, or
by directly inputting the tens, units and decimal digits on the keypad, in that order. Following is a
description of the states and functions of the local finite state machine.
Local FSM States:
● Select_temp This is the default state of this finite state machine. In this state, the
cursor (#) is displayed next to the temperature setpoint on the display. This indicates that,
the setpoint for the temperature can be modified by pressing the 2nd key on the keypad.
● Select_hum Displays the cursor (#) next to the humidity setpoint. This allows the user
to modify the setpoint for humidity by pressing the 2nd key on the keypad.
● Set_temp This state allows to modify the setpoint for temperature. There are two ways
of doing this. By using the up or down keys on the keypad, or by directly inputting the
digits for the setpoint. This state advances based on the first input from the user. Using
the up or down key modifies the measurand in 0.1 increments
● Set_hum This state allows to modify the setpoint for temperature. There are two ways
of doing this. By using the up or down keys on the keypad, or by directly inputting the
digits for the setpoint. This state advances based on the first input from the user. Using
the up or down key modifies the measurand in 0.1 increments
● Tens_T Upon entering the first digit in set_temp state, tens_T waits for the next digit to
be put in the units place.
● Units_T This state waits for decimal digit to be input on the keypad.
● Dec_T This state waits for the Enter key to be pressed and then updates the
temperature setpoint of the EMCS and updates the display accordingly.
● Tens_H Upon entering the first digit in set_hum state, tens_H waits for the next digit to
be put in the units place.
● Units_H This state waits for decimal digit to be input on the keypad.
● Dec_H This state waits for the Enter key to be pressed and then updates the humidity
setpoint of the EMCS and updates the display accordingly.
Local FSM Functions:
● move_cursor_hum Set the variable boolean hashtag equal to 0. The main function
then used this variable to display the cursor next to the humidity setpoint.
● move_cursor_temp Set the variable boolean hashtag equal to 1. The main function
then used this variable to display the cursor next to the temperature setpoint.
● increment_ST Incremented the value of the temperature setpoint by 0.1 degrees.
● decrement_ST Decremented the value of the temperature setpoint by 0.1 degrees.
● update_ST Set the flag, entered, equal to 1, enabling the main program to update the
temperature setpoint displayed on the LCD display.
7. SAAT Corporation
Your Home Environment Monitoring System 6
● increment_SH Incremented the value of the humidity setpoint by 0.1%.
● decrement_SH Decremented the value of the humidity setpoint by 0.1%.
● update_SH Set the flag, entered, equal to 1, enabling the main program to update the
humidity setpoint displayed on the LCD display.
● process_digit Depending on the current state of the state machine, this function used
the keycode value obtained from the keypad to change the respective digit of the
temperature or humidity setpoints. It then updated the value of the global variables for the
two setpoints.
● do_nothing This function does nothing in the state machine and simply prints “Do
Nothing”. This function is used for testing and debugging the state machine.
9. SAAT Corporation
Your Home Environment Monitoring System 8
Remote Operation Mode FSM
This Finite State Machine implements the operations of the EMCS in Local operation
mode. The commands are transmitted and data is received through an XBee module using
RS232 protocol. The following is the command set for the EMCS in remote operation mode:
To set temperature: ST=dd.d
To set humidity: SH=dd.d
To read temperature: T
Response is: T=dd.d
To read humidity: H
Response is: H=dd.d
To read pressure: P
Response is: P=dd.dd
where d is a digit 09.
Commands sent by the device cloud are wrapped by a Return Carriage char ‘/r’. Following is the
description of the remote FSM:
Remote FSM States:
● display Initial state of the system that waits for an incoming command to be executed.
The input command is saved in a buffer to be able to be accessed later in the system.
● send_temp When the carriage return char ‘/r’ is received, this state returns the
temperature and goes back to the initial state display.
● send_pressure When the carriage return char ‘/r’ is received, this state returns the
pressure and goes back to the initial state display.
● send_humidity When the carriage return char ‘/r’ is received, this state returns the
humidity and goes back to the initial state display.
● process_second If the first character received was an ‘S’, the following command
must be modifying one of the setpoints. This state waits for the second character to
determine if temperature setpoint or the humidity setpoint is to be modified.
● wait_H This state waits for an ‘=’ character.
● tens_H This state indicates that the next character received is the tens digit of the
humidity setpoint. The present state variable is used by the process_digit function to
determine what position the digit is in.
● ones_H This state indicates that the next character received is the units digit of the
humidity setpoint.
● dot_H Waits for a decimal point to be entered after the units digit.
● stay_H Waits for a valid digit to be entered for the decimal digit of humidity setpoint.
● decimal_H Waits for a carriage return character to update the humidity setpoint and
return to the initial state of the system.
● wait_T This state waits for an ‘=’ character.
10. SAAT Corporation
Your Home Environment Monitoring System 9
● tens_T This state indicates that the next character received is the tens digit of the
temperature setpoint.
● ones_T This state indicates that the next character received is the units digit of the
temperature setpoint.
● dot_T Waits for a decimal point to be entered after the units digit.
● stay_T Waits for a valid digit to be entered for the decimal digit of temperature setpoint.
● decimal_T Waits for a carriage return character to update the temperature setpoint and
return to the initial state of the system.
Remote FSM Functions:
● save_command Saves the incoming character in a buffer to be accessed later.
● return_temp Sends the temperature measurement out to the remote station in the
format: T=dd.d.
● return_pressure Sends the pressure measurement out to the remote station in the
format: P=dd.dd.
● return_hum Sends the humidity measurement out to the remote station in the format:
H=dd.d.
● process_digitR Depending on the present state of the machine, this function used the
digit to update the respective digits of one of the setpoint values.
● send_SH The new humidity setpoint is updated and displayed on the LCD screen on
the device.
● send_ST The new temperature setpoint is updated and displayed on the LCD screen
on the device.
14. SAAT Corporation
Your Home Environment Monitoring System 13
EAR DOG Module LCD
The EAR DOG Module DOGM163WA used in this system is a SPI LCD display
controller and driver with a 3 line 16 character dot matrix LCD panel. The controller has two 8bit
registers, the instruction register (IR) and the data register (DR). The controller has parallel
interface but it is also SPI compatible. In this system SPI is used to write to the display. The
Register Select input (RS) selects the IR when RS = 0 and the DR when RS = 1. The IR stores
instruction codes and address information for the DDRAM and Character Generator RAM
(CGRAM). The DR holds the data to be written to the DDRAM or CGRAM. The address counter
register (AC) holds the address of the locations in DDRAM or CGRAM.
Figure 7: LCD DOG Module connections
Courtesy: Professor Kenneth Short’s lecture slides
The MOSI and SCK signals of the DOG module are shared by other SPI peripherals in the
system. The RS signal is connected to the PB4 of the ATmega128. The LCD chip select signal
(/SS) is connected to PB0. These connections are made using a JTAG connector shown below.
Figure 8: LCD JTAG Connector
15. SAAT Corporation
Your Home Environment Monitoring System 14
Honeywell HumidIcon Temperature and Humidity Sensor
This design uses a Honeywell HIH9000 series SOIC8 SMD with serial output. This
sensor is a combined temperature and humidity sensor with 14bit resolution. In a measurement
cycle, the sensor is normally in power down mode. To wake the sensor and make a
measurement, a Measurement Request (MR) command is used. A MR command is an 8bit
read and then incoming data is ignored. A Data Fetch (DF) command is then used to read the
temperature and/or humidity.
Figure 9: HumidIcon Measurement Cycle
Courtesy: Professor Kenneth Short’s Lecture Slides
The sensor is a Read only device and uses the shared MISO input from the
microcontroller. Pin PortA 0 is used as a select signal for the sensor. A data fetch packet
returned from the humidicon has the following format: [ {S(1:0),C(13:8)}, {C(7:0)}, {T(13:6)},
{T(5:0),xx} ] where,
S(1:0) = Status bit of the packet (00 normal operation, valid data; 01 stale data, no new data)
C(13:8) = Upper six bits of the 14bit humidity
C(7:0) = Lower eight bits of the 14bit humidity
T(13:6) = Upper eight bits of the 14bit temperature
T(5:0) = Lower 6 bits of the 14bit temperature
xx = don’t care.
Figure 10: Humidicon Data packet
Courtesy: Professor Kenneth Short’s Lecture Slides
Hence, a complete measurement of both temperature and humidity takes a total of four SPI
transfer cycles. This raw data is then scaled and converted to the required units to be displayed.
16. SAAT Corporation
Your Home Environment Monitoring System 15
Figure 11: HumidIcon Schematic
Conversion and Scaling of Raw Data
1. The four data packets are stored in 4 separate unsigned integers. Using the above
notation, C(13:8), C(7:0), T(13:6), T(5:0) are to be stored in separate variables C1, C2,
T1, T2, respectively.
2. Mask the C1 with 0x3F to eliminate the two unnecessary MSB of C1 that do not contain
the value of the raw humidity.
3. Mask T2 with 0xFC to eliminate the two unnecessary LSB of T2 that do not contain the
value of the raw temperature.
4. Shift C1 to right 8 positions to place the high nibble of the raw humidity into the MSBs.
5. Shift T1 to the right 8 positions to place the high bible of the raw temperature into the
MSBS.
6. Performing a bitwise OR of C1 and C2 will yield the complete raw value of Humidity.
7. Performing a bitwise OR of T1 and T2 will yield the complete raw value of temperature,
after the OR result is shifted to the left two position.
(1)caled Temperature 000S = 2 −214
Raw Temperture 100 165* *
− 4
(2)caled Humidity S = 2 −214
Raw Hiumidity 100 100* *
See files humidion _task2.c and temp_humid_humdicon.c in the appendix to see process
executed in C.
17. SAAT Corporation
Your Home Environment Monitoring System 16
Pressure Sensor
The transducer used in this system is a Freescale MPXHZ6130A Pressure sensor. This
sensor has a 1.5% accuracy over 0 degrees to 85 degrees Celsius. It comes in a surface mount
package and is suitable for microcontroller based systems. The basic characteristics of the
sensor are shown in the table below from the datasheet:
Figure 12: MPXHZ6130A Pressure Sensor Characteristics
Courtesy: MPXHZ6130A Datasheet
The analog output of this sensor is connected an AnalogtoDigital converter.
Figure 13: MPXHZ6130A Schematic
18. SAAT Corporation
Your Home Environment Monitoring System 17
MAX1270 Analog-to-Digital Converter
The MAX1270 is a DataAcquisitionSystem (DAS) IC that has a multiplexer, to switch
between input channels, signal conditioning circuit for gain and offset adjustment, and an
AnalogtoDigital converter with Voltage reference. It allows up to eight analog input channels. It
has a 12bit resolution with 0.5 LSB linearity Our system uses a SPI enabled version to save port
pins on the microcontroller. This is used to convert the analog pressure sensor output to a digital
output to be monitored and used by the microcontroller. Channel 0 analog input is used in our
system.
To initiate a conversion, a Control Byte needs to be transmitted. The control byte selects
the input channel for a particular conversion, selects the full scale input voltage range, unipolar or
bipolar modes, and the clock and power down mode. The control byte has the following format:
CB = {Start, SEL2, SEL1, SEL0, RNG, BIP, PD1, PD0}
Bit 7 Start: First logic 1 after the /CS goes low defines the beginning of a control byte.
Bit 6:4 Select bits: The three bits select the desired analog input channel.
Bit 3 Range: Selects the full scale voltage range for the conversion. (Table __)
Bit 2 Bip: Unipolar or Bipolar operation mode (Table __)
Bit 1:0 Power Down mode: 00 for normal operation (always on) with internal clock.
Table 1: Range and Polarity selection for MAX1270
Courtesy: MAX1270 Datasheet
The timing waveform below from the MAX1270 datasheet shows the detailed timing
requirements. After the Chip Select input (/CS) signal goes low, the control byte for a conversion
is transmitted. After the transfer of the control byte, the chip is to be unselected (/CS=1). This
sets the Strobe signal (SSTRB) to a logic 0 indicating the start of a conversion. The end of
conversion is indicated by the SSTRB signal going high. Once the SSTRB signal goes high, our
design transfers two dummy bytes over the MOSI line to read the 12bit ADC output over the
MISO line. For faster continuous conversion cycles, a second control byte can be transferred
after the first dummy byte to initiate another conversion. However, our system does a total of
three byte transfers, one control byte and two dummy bytes. At the end of the second dummy
byte, the chip is deselected. INT1 of the microcontroller is used to trigger an interrupt service
routine when end of conversion signal occurs on the SSTRB.
20. SAAT Corporation
Your Home Environment Monitoring System 19
XBee Wireless Module
The XBee 802.15.4 wireless transmitter/receiver converts RS232 protocol signals into a
wireless RS232 protocol data stream. In remote operation mode of the EMCS, the XBee is used
to receive commands from a remote station and send data back. This enables the setting of
temperature and humidity setpoints from any internet capable device. The ATmega128 uses
USART0 to communicate with the XBee module. The base station sends out a command
through the USART, which then goes to the XBee for wireless transmission. A remote station is
also able to send commands back to the base station through a device cloud that is integrated
with the XBee. The Heroku cloud application platform provides for customized device cloud
capabilities. The XBee module comes with its own device cloud. Logging into the Heroku device
cloud for XBee gives us loads of capabilities via widgets to communicate with the XBee. Our
system uses a simple text interface that is able to send and receive data from the XBee module
over the internet.
The Xbee needs a 3.3V power supply. Since this system is primarily 5V, a voltage
regulator is used to convert 5V down to 3.3V. Because the XBee is operating at 3.3V, it cannot
be directly connected to the ATmega128. The voltage and current characteristics of both the
devices need to be compatible. The XBee RxD input from the microcontroller is connected to a
voltage divider to limit the voltage.
Figure 16: XBee ATmega128 Compatibility Requirements
Courtesy: Professor Kenneth Short’s Lecture Slides
22. SAAT Corporation
Your Home Environment Monitoring System 21
Troubleshooting
Issue Possible Reason How to fix it
LCD does not turn on System is not powered Check if the power cord is
connected properly.
Disconnect and connect it.
Battery out of power,
replace the battery
LEDs do not turn on Measurands and setpoints
are equal
If the measurands and
setpoints are equal, the LEDs
do not turn on. This is not a
problem
Wrong measurand readings Calibration Power off and power on the
system again to reset it
Device disconnected on
Heroku device cloud
Device not connected to wifi Ensure your wifi is open and
available to connect. If not,
contact your network
administrator.
Cannot log on to device cloud Wrong username/password Ensure the correct
username and password
Contact Heroku Tech.
Support for further details:
9529123444
Other unknown issues Contact us at 6315555555
to report the issue for further
assistance
Contact Information
Email
questions@SAAT.com
Phone
1800888SAAT(7228)
Mail
SAAT Corporation
1, Infinity Way
Port Jefferson, NY 11790
