S16: Simpsons

Grading Criteria

• How well is Software & Hardware Design described?
• How well can this report be used to reproduce this project?
• Code Quality
• Overall Report Quality:
  • Software Block Diagrams
  • Hardware Block Diagrams

    Schematic Quality

  • Quality of technical challenges and solutions adopted.

Abstract

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Objectives & Introduction

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Team Members & Responsibilities

• Gaurao Chaudhari
• Akshay Kanchar
  • Key Locator
• Keerthana Alugudurai
  • Haptic feedback
• Bhushan Muthiyan
  • Haptic feedback
• Arvind Allawadi
  • GSM module

Schedule

Sl. No	Start Date	End Date	Task	Status	Actual Completion Date
1	04/05/2016	04/12/2016	1) Buying of blind stick and other important components 2) Development and Design of Software and Hardware Architecture	Completed	04/11/2016
2	04/12/2016	04/19/2016	1) Interfacing Sensors,Vibrators,Buttons and GSM with SJ One Board 2)Developing basic functionalities for Sensors and Vibrators	Completed	04/20/2016
3	04/19/2016	04/26/2016	1) Interfacing,implementation and integration of GSM module 2) Implementation of Key Locator functionality	Completed	04/28/2016
4	04/26/2016	05/03/2016	Completing Integration of all modules and testing basic obstacle avoidance and haptic feedback	Completed	05/05/2016
5	05/03/2016	05/10/2016	Testing and resolution of Problems	Completed	05/12/2016
6	05/10/2016	05/17/2016	Final testing	In Progress

Parts List & Cost

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Design & Implementation

Key Locator

Hardware Design

A in-built Nordic wireless is used for board to board communication.The transceiver used is nRF24L01+ Single Chip 2.4GHz Transceiver. Figure() shows the connection of the transceiver with the SJ One controller.

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The boards communicate via 2.4 GHz RP-SMA Duck antennas. Figure() shows the connections of these antennas.

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Hardware Interface

The hardware interface is fairly simple. A small 5V battery powers key via its on board 5V pins.The antenna is connected to the SJ One board via its SMA connector.The Nordic wireless has the following connections with the controller. SPI bus is used for communication between them.

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Software Design

The software design is divided into two parts:

1) Key Transmitter : A Free-RTOS task is used to detect key press by the user.

2) Key Receiver  : A Free-RTOS task is used to detect signal received on the Cane.On receiving the signal, a call is made to the sound buzzer.

Implementation

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GSM Module

This module consist of a GSM/GPRS Sim900 modem and a press button (panic button) mounted on the stick. This GSM modem accepts a full size SIM card and can communicate using AT (Attention) commands sent from the micro controller (LPC 1768, SJone board) through UART interface at a baud rate of 115200 bits per seconds. This module requires 5 volts in order to work properly. In an emergency situation, the stick owner must press this button which will send an SMS to a registered user to take care of the blind person.

There are two led's on the modem, namely power and sync. Once the 5 volt power supply is given, this light will turn on, and the sync led will start blinking as well. However, this sync led is very useful during testing and making sure that the SIM card has been registered on the network. If the SIM card has not been registered on the network, and/or not been inserted into the modem yet, the sync led will blink at a rate more than once every second. After the SIM card is registered the rate of blinking reduces to as low as once every three seconds.

Hardware Design

The hardware design for this module includes a GSM/GPRS Sim900 module and a switch both connecting to a common SJ one micro controller.

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Hardware Interface

The communication protocol of GSM module with the controller is through UART which requires four wires to establish a serial communication- Rx, Tx, Ground and Vcc. Figure() shows the connection of the GSM module with the SJ One controller.

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A switch used as a panic button will be used as an interrupt to the controller board's GPIO pin, which will initiate the routine to send the AT commands to the GSM module necessary for sending SMS to a cellular phone.

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Software Design

The software design for this module will include only a panic task. This task will monitor if a stick owner has pressed the panic button or not. If the button is pressed, then the controller will send a set of AT commands required to enable GSM module to an SMS mode and be able to send a desired SMS to the cellular phone.

The essence of writing code for the GSM module is the proper usage of AT commands provided by the GSM manufacturer. GSM modem understands the AT commands, which are used as a prefix with every command send to it and followed by a carriage return (\r character from the controller). The SIM900 modem implements the combination of GSM07.05, GSM07.07, V.25ter, and the AT commands developed by SIMCom. Syntactically, AT commands can be split into three categories, but the most used ones, that are also used for this project are: basic and extended.

Basic AT commands: These are the commands which are used to do basic operations such as Dial (ATD), Answer (ATA), Hang up (ATH), etc which are also used for dial-up modems.

Extended AT commands: Besides the basic commands set there are commands which are specific to the GSM technology. These commands can operate in different modes such as test, read, write, and execution mode. All the extended commands starts with AT and ends with carriage return.

Configure the GSM module for sending SMS:

a) Sending to a single subscriber (one message)

1. AT<Carriage Return>. A response of OK means that connection between controller and modem is working fine.
2. AT+CMGF=1. This tells the modem that the text mode for the SMS should be used, where as the other mode, PDU, can be set by setting the value to 0.
3. AT+ CMGS= "1530*****61" <Carriage Return> =>message <ctrl-z>. This is the format for sending an SMS by using +CMGS command.

b) Sending to multiple subscribers

It will be a choice for a stick-owner to choose if he has to send an emergency message to a single person, or there is more than one person to whom he wants to issue the message. In case of multiple senders, sending using +CMGS is not as efficient, as it may take upto a min. from the time blind person presses the panic button to the time it reaches to his 4th friend. In case of issuing the same message to multiple cell phones, sending a message from storage is more efficient. Below is the sequence of the AT commands from sending from SIM storage.
1. AT
2. AT+CMGF=1. For SMS mode
3. AT+CPMS="SM","SM". Format for +CPMS is +CPMS=storage1[,storage2[storage3]]. Messages are read and deleted from storage1. Messages are written to storage2. Storage3 defines the memory location to store the received messages. However, if we are not concerned with receiving text, we can ignore this optional parameter.
4. AT+CSCA="+12063130004”. This AT command is to set the SMSC address to where the messages are sent first and dispatched for the destination number. For T-mobile network this number is +12063130004. This # can be found from the cell phone in the message settings.
5. AT+CMGW="1530*****61",129,"STO UNSENT" <Carriage Return> Message <ctrl-z>. This AT command writes the messages to the memory space provided in the above +CPMS command. Second and third parameters are optional. First parameter is the destination number which is stored along with the message as well. Important point to note is that the message required to be written to the SIM only once. Once the message has been written to the particular index, this write function may not be required to call.
6. AT+CMSS=1,"1530*****61". +CMSS is used to send a message from the storage. First parameter of +CMSS is the index of the memory location from where to send the message. Second parameter is to where to send the message.

Other useful AT commands that were used during the testing as well as for the final code sequence of the AT instructions:

1. AT+CSCS = "GSM". SIM900 defaults to IRA character set. This AT command change it to GSM character set.
2. AT+CMEE = 2. This command is used to get the indication of an error related to the ME functionality. Parameter 2 enables the +CME error in verbose form. For example, +CME error: sim is not inserted. However, 0 parameter value is default and used to disable +CME error, only 'error' is displayed in case of some error.
3. AT+CREG=2;AT+CREG=?. This command is used to tell whether the SIM card is registerd on the network. parameter 2 we get the registration result with the location information.
4. AT+CMGR=1;AT+CMGD=1,4. +CMGR is used to read the messages from the memory storage. Whereas, +CMGD is used to delete messages from the storage. First parameter is the index of the memeory location in both instructions, however parameter 4 in +CMGD implies to delete all the messages. Other parameters (0-4) can be used as per requirement.
5. AT + CPIN?. This command may come handy when for example your sim requires a password. For us, we got the response READY, indicating that SIM is good to use, and has no kind of passwords, such as SIM PIN or SIM PUK.

Implementation

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Haptic Feedback

This module consist of a haptic vibrator.

Hardware Design

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Hardware Interface

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Implementation

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Testing & Technical Challenges

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My Issue #1

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Conclusion

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Project Video

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Project Source Code

• Sourceforge Source Code Link

References

Acknowledgement

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References Used

Nordic Wireless [1]

Appendix

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