IV - BS Computer Engineering
March 14, 2008
GSM Module
MAX-II Starter Kit
Personal Computer
MAX550 & MAX1240
Possible Applications

Remote Data Acquisition and Control via SMS





The objective of this project is to bridge the gap between man and machine. For this project, the group was able to translate user commands to something that the machines to understand. Nonetheless, it also translates the machine’s status to something the users can understand.

Cellular phone users can send SMS messages to the GSM module. Given this input, the control unit sends specific output to the machine depending on the machine and what is instructed. On the other hand, seeing it in the reverse, the machine can input its status to the control unit through the ADC. This time, the control unit will send SMS messages to the user through the GSM module.
  • Analog to Digital Converter – Converts Voltage readings to binary data. Its output is fed to the LPT port of the PC or certain predefined pins of the Microcontroller.

  • Digital to Analog Converter – Converts binary data to a Voltage output. Several predefined pins of the Microcontroller control it
  • Relay (with Amplifier) – Shorts or Opens a connection based on the Voltage value fed to the Amplifier (BJT’s base). The Voltage state at the Amplifier’s input is connected to a specific pin on the PC’s LPT Port (status register) or a predefined pin on the Microcontroller.
Setup of the Project
Figure 1: Setup of the Project.
Figure 2: Flow Chart of the Project.
GSM Module
Figure 3: The GSM Module.
GSM Module
The GSM Module is a kit purchased from e-gizmo. It is capable of Text Message reading, sending, and storage. Furthermore, it can make Data or Voice calls and also receive them. It can be controlled using predefined AT Commands.

  • AT+CMGF=1 – Message Function Set to Text
  • AT+CMGL=”REC UNREAD” – Reads All Unread Messages
  • AT+CMGS=”phone_number”(CR) >TEXT(Ctrl + Z) – Sends Message “TEXT” to phone_number
  • ATDphone_number – Makes a Data Call to phone_number
MAX-II Starter Kit
The MAX II starter kit emulation board is based on Altera’s EPM1270 Complex Programmable Logic Device (CPLD). It provides up to 1270 logic elements (LE), 116 I/O lines and 8-Kbit user flash memory. Altera’s Quartus II software is used for programming the MAX II.

  • 4 Digitals seven segment LED Displayer
  • 8 Bits DIP Switch
  • 4 Push Buttons
  • 8 LEDs
  • 1 16Mhz Oscillator
  • 1 UART Connector
  • 4 Extension I/O Connectors
  • 44 Pin Socket (for 3.3V 8051 CPU)
Figure 4: MAX-II Starter Kit.
Figure 5: Screenshot of the C# program.
The group used C# to control the GSM Module. A screenshot of the output is shown on Figure 5.
It is an 8-Bit Analog to Digital Converter. It has a maximum of 5V. However, if one wants to measure voltages in excess of 5V, a simple Voltage Divider Circuit may be used such that:
equation 1
Thus, the reading measurement could be handled by the ADC, yet is still proportional to Vmax.
Figure 6: Schematic Diagram of Free-Running ADC0805.
Figure 7: MAX1240.

Figure 8: MAX550.
MAX550 & MAX1240
The MAX550 is a Digital to Analog Converter that is generally used with the Max-II. It has a serial interface thus it uses only one pin to receive the actual data from the microcontroller. The microcontroller then has to convert the parallel data to serial.
The MAX1240 is similar to the MAX550; however, since it is an Analog to Digital Converter, it sends data in serial. Then, the microcontroller uses a shift register to store these bits and read them in parallel (after the complete string of data is completed).
Both the MAX550 and the MAX1240 are integrated into a board designed by Blue Chip Designs Inc. This provides the user with a ready-to-use ADC and DAC that can easily be interfaced with the MAX-II.

Figure 9: Actual Circuit.
The relay used is a Dual Pole Dual Throw (DPDT) 12V relay that is driven by a BJT amplifier (since digital outputs are either 3.3V or 5V). For more sensitive designs wherein factors such as temperature are a concern, the Amplifier in Figure 11 is recommended. However, for our test circuit and other less complex applications, Figure 12 is enough.
Figure 10: Actual Ciruit for the Relay.
Figure 11: Relay.
Figure 12: Relay.

Possible Applications
  1. Theft Deterrent for Automobiles – The relay can be hooked up to the fuel pump. When the car is stolen, the user can text “Relay 0” to the module which would in turn shut down the car. The alarm feature of the module may also be of great help. Furthermore, it can be used to monitor various values such as speed, battery power, fuel level etc. (c/o ADC).
  2. House Sentry – The module itself can control various aspects of the house it is guarding. A number of inputs can be hooked up to the ADC or the pins themselves (e.g. smoke detector, fire alarm, temperature sensor etc.) Like in the previous example, it can be used to turn on alarms, lights, appliances, video monitoring systems, or even possibly lock/unlock the entire house.
  3. Solar Panel Controller – By interfacing it with the mechanisms that pan and tilt solar panels, it can be used as a means to maximize the amount of energy that can be accumulated by these panels and even monitor the status of their batteries. Through readings from the ADC and other inputs, it has the ability to decide which course of action should be done and it can send data or commands to technicians and other set-ups practically anywhere.
  4. Other Small Scale Applications
    • The ADC can be hooked up to the LM35 temperature sensor (by measuring the voltage drop produced across a resistor).
    • The DAC can be used to control FETs that would in turn act as a current sources.
    • The Relay can be hooked up to high power circuits without fear of destroying the module (due to isolation).
    • The Module itself can be programmed to control servos, and stepper motors.
    • The Module can also be used as a timer/delay for any of these applications.