barcode reader in asp.net AVR PROJECT 5: RADIO BEACON CONTROLLER in Software

Maker Code-128 in Software AVR PROJECT 5: RADIO BEACON CONTROLLER

250 AVR PROJECT 5: RADIO BEACON CONTROLLER
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Yes Power on RESET No Yes External RESET No (must be watchdog reset) Incr software counter Initialize Ports, Stack pointer reset software counter
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Yes counter=MAX_COUNT
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Execute Morse Message Output
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Enable watchdog
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FIGURE 14.4 Flowchart for the beacon controller program.
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14.5 Fabrication
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The system was fabricated on a general-purpose PCB as illustrated in Figure 14.6. Since the whole system is very small, fabricating the circuit was quick and easy.
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14.6 Design Code
The design code for the beacon controller was developed using the flowchart illustrated in Figure 14.4. The code was split in small subroutines. Initially, the system code to check the watchdog reset and to distinguish the watchdog reset from power-on reset was written and tested. The Morse code generation subroutine was tested separately and then integrated into the main program. A table that encodes the Morse code was created and stored as program memory data and stored in the flash program memory. The actual message was
DESIGN CODE 251
FIGURE 14.5 Circuit schematic for the radio beacon controller.
252 AVR PROJECT 5: RADIO BEACON CONTROLLER
FIGURE 14.6 Photograph of the beacon circuit board.
stored in the EEPROM as index into the Morse table. Since the EEPROM is 128 bytes, a message of up to 128 characters can be stored and generated by this system. The code for this project is available in the code directory in the file mtutor1.asm.
14.7 Testing
The system was tested using standard test equipment. One easy test was the fact that the system could generate correct audio tone for the stored message. Figure 14.7 shows the Morse audio side tone signal and RF oscillator key switch output generated by the controller.
TESTING 253
Audio sidetone output Transmitter Key switch output
FIGURE 14.7 Scope trace for the audio sidetone as well as the transmitter key switch output generated by the beacon controller. The trace shows four Morse codes for the characters C Q C Q.
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AVR PROJECT 6: ASTRODAT: A STAND-ALONE DATA ACQUISITION SYSTEM
15.1 At a Glance
All about data acquisition systems
1. Describe a matchbox-size low-power DAS using only 3 ICs 2. A complete DAS for astronomical applications 3. An OS-independent readout using an RS-232 port
15.2 Introduction
There are occasions when it is necessary to record data in an unattended manner over extended periods of time.1 Such requirements can often be met with a suitable data acquisition system connected to a PC. Often enough, there are occasions to log such data in remote wilderness with no access to suitable power. Such requirement can be met with an autonomous data acquisition system that runs off battery power.
1As Ambrose Bierce might have said, The code presented in this chapter was developed by Saurabh Jain and Smita Mohan and to whom is rightly due the credit for the merit that it may have.
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256 AVR PROJECT 6: ASTRODAT: A STAND-ALONE DATA ACQUISITION SYSTEM
Figure 15.1 illustrates the block diagram of a PC-hosted data acquisition system. The data acquisition hardware contains suitable electronics front-end circuitry to digitize the input analog data. The converted digital data is uplinked to the PC through the connecting link between the PC and the data acquisition hardware. The link itself could be serial (RS232, RS-485, USB, IrDa) or parallel (parallel port, ISA expansion card). The PC software would acquire, store, and eventually process the acquired data. As mentioned above, the problem with this setup lies in meeting the power requirements for running the PC and the data acquisition hardware in remote locations not to mention the security needs of such a setup. To some extent the power requirements could perhaps be solved by using a Notebook PC, but not for extended periods of time. When it comes to low power, extended-period-acquisition applications, nothing beats the setup illustrated in Figure 15.2. The controller is armed to acquire data in the required format (which includes such information as the sampling rate, etc.) and then taken to the site where the acquisition takes place. Upon completion of the acquisition activity, it is brought back to civilization and the stored data is read out to a PC for analysis. In this chapter we look at a couple of such data acquisition system designs. The next section describes a simple paper design using an 1-channel 12-bit ADC and serial EEPROM for data storage. EEPROMs are available in 64-Kbyte capacity in 8-pin DIP packages, and up to 4 of these can be cascaded to give 256-Kbyte storage. The data is stored in the EEPROM and can be read out through the PC parallel port in a novel way. Using EEPROM has an operational advantage: It can retain data even in the absence of power. However, there is a caveat: EEPROMs cannot be written as fast as conventional SRAM, and this is a disadvantage that one has to live with. It is, however, possible to alleviate this problem to some extent by employing buffer memory, but again at a cost of increasing system complexity or increasing the number of EEPROMS and striping the data storage across the EEPROMs. Later, I describe a complete and tested DAS that is specifically designed for use in astronomical applications. It can also be used elsewhere without any change. However, the keyword in the design of both the systems is simplicity. Both of the designs have a single and critical design objective:
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