Design Project - Purdue University



Homework 5: Theory of Operation and Hardware Design Narrative

Due: Friday, September 28, at NOON

Team Code Name: _µ[sic]____________________________________ Group No. _5___

Team Member Completing This Homework: _Josh Speciale________________________

e-mail Address of Team Member: _jspecial_____ @ purdue.edu

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Evaluation:

|SCORE |DESCRIPTION |

|10 |Excellent – among the best papers submitted for this assignment. Very few corrections needed for version submitted in |

| |Final Report. |

|9 |Very good – all requirements aptly met. Minor additions/corrections needed for version submitted in Final Report. |

|8 |Good – all requirements considered and addressed. Several noteworthy additions/corrections needed for version |

| |submitted in Final Report. |

|7 |Average – all requirements basically met, but some revisions in content should be made for the version submitted in the|

| |Final Report. |

|6 |Marginal – all requirements met at a nominal level. Significant revisions in content should be made for the version |

| |submitted in the Final Report. |

|* |Below the passing threshold – major revisions required to meet report requirements at a nominal level. Revise and |

| |resubmit. |

* Resubmissions are due within one week of the date of return, and will be awarded a score of “6” provided all report requirements have been met at a nominal level.

Comments:

Comments from the grader will be inserted here

1. Introduction

The µ[sic] system will provide a unique wireless media solution that allows users to carry their favorite music with them on a portable media drive and potentially have it played from a nearby base station, wherever it may be. Both the mobile and stationary components of the system require modules and circuitry to enable the transmission and storage of media files, and the function of the base station necessitates audio decoding and output circuitry. The portable media drives need circuitry that allows the system to run off of battery power but also be able to recharge a battery.

2. Theory of Operation

With the exception of the LCD screen on the µ[sic] base station unit, all components are capable of operating at 3.3 volts. Five-volt input from a “wall wart” will be used to power the LCD module and will pass through a Maxim MAX1818 low-dropout linear regulator to provide the 3.3 V necessary for the rest of the system [1]. The portable media drive (PMD) units feature a 3.7 V Tenergy PL-383562-850 850 mAh lithium-ion battery and a Maxim MAX710 DC-DC step-up/down regulator to provide a consistent 3.3 V supply as required by all PMD components [2][3]. The MAX710 will send a low battery (LBO) signal to the microcontroller when the output voltage of the battery crosses a configurable threshold — 2.8 V for this design. This signal will be used within the microcontroller to control the status of a multi-purpose indicator LED on the PMD. A Maxim MAX1811 chip handles charging of the battery. When the PMD is plugged in via a mini-USB port, the MAX1811 will use the 5 V supplied there to charge the battery and “take over” the task of powering the PMD through the MAX710 regulator. The MAX1811 features a charge status output (CHG) to the microcontroller [4].

The base station and portable drive units of the µ[sic] system will make use of identical circuits for data memory and wireless communication (with the exception of microcontroller pin assignments). Both of these subsystems will communicate with the microcontrollers using a serial peripheral interface (SPI), and the microcontrollers will be using two general-purpose I/O pins as slave select signals in these circuits. The microSD flash cards will operate in “SPI mode,” allowing six-byte control commands to be sent serially from the microcontrollers [5]. Similarly, the Mitsumi WML-C40 Bluetooth module will interact with the microcontrollers and other Bluetooth modules via the Hayes (also referred to as “AT”) command set [6]. The AT commands and responses will be transmitted and received serially from and to the microcontroller.

The user interface on the base station consists of four buttons, three LEDs, and the LCD. The buttons and LEDs will be simple pull-up or pull-down and inputs will be debounced in software. The Crystalfontz CFAH2004A-TFH-JP LCD module will be controlled by three outputs from the microcontroller and will receive data through eight pins on the microcontroller [7]. The PMD system will feature only four LEDs for output to the user; these will all be assigned to general-purpose I/O pins.

The final subsystem in the base station is the audio output circuit. The AT89C51SND1C microcontroller will send clocking, channel selection, and PCM data signals to the Texas Instruments PCM1770 digital-to-audio converter [8][9]. The PCM1770 will output two-channel line level audio.

3. Hardware Design Narrative

The Atmel A89C51SND1C microcontroller in the base station will utilize port one for interfacing with the LCD; all eight pins will be initialized to output data signals to the display module. Control signals for the LCD will originate from pins five through seven on Port 2. Port 2 also houses the LED indicators and slave selector pins for SPI interfacing — pin zero (P2.0) is the slave select signal for the SD Flash card socket and pin one (P2.1) the slave select for the Bluetooth module. Port 4 is the SPI module on the microcontroller, and the pins on this port connect with their respective pins on the Bluetooth module and the microSD Flash card socket. The subsystems connected via SPI will be configured in such a way that only ASCII commands will be required for communication. The other pins utilized on the C51 controller are the audio output pins from the embedded MP3 decoder. The decoder outputs signals for system and data clocking (SCLK and DCLK), left and right channel selection (DSEL), and the PCM audio data (DOUT) to the corresponding pins on the PCM1770 DAC — SCKI, BCK, LRCK, and DATA, respectively. Port 3 and Port 5 can be utilized for future functionality expansion of the µ[sic] device.

The Atmel ATmega644 microcontroller on the PMD will initialize only two ports. Port A will be set as a general input and output port for the system. Pins zero and one on Port A will be slave select output signals for the two SPI devices. Pins four through seven are set aside as output signals for the LED indicators on the PMD. Pins two and three on the port are reserved as inputs from the power management system of the chip. These will allow for indication of when the battery charge is low and when the battery is actively charging. Port B on the ATmega644 is the SPI module. The SPI is, as mentioned previously, used for interfacing with the microSD Flash card and the Bluetooth module on the PMD. Pins five, six, and seven on this port will connect to the appropriate SPI pins on the flash memory socket and the Bluetooth module. Ports C and D on the ATmega644 are not initialized, reserved for any necessary future expansion.

4. Summary

This report has briefly summarized the major subsystems within the µ[sic] base station and PMD units and discussed their interconnections with the systems’ microcontrollers. What and how signals are passed to the microcontrollers for proper functionality of the subsystems was discussed, as well as which microcontroller ports would need to be utilized in order to realize the system functions.

List of References

1] Maxim MAX1818 Data Sheet,



2] All-, PL-383562-850 Page



3] Maxim MAX710 Data Sheet,



4] Maxim MAX1811 Data Sheet,



5] Maxim Integrated Products, Application Note 3969, “SD Media Format Expands the MAXQ2000's Space for Nonvolatile Data Storage,”



6] SparkFun Electronics, “The DIP Module,”



7] Crystalfontz CFAH2004A-TFH-JP Data Sheet,



8] Atmel AT89C51SND1C Data Sheet,



9] Texas Instruments PCM1770 Data Sheet,



Appendix A: System Block Diagram

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NOTE: This is the second in a series of four “design component” homework assignments, each of which is to be completed by one team member. The completed homework will count for 20% of the individual component of the team member’s grade. The body of the report should be 3-5 pages, not including this cover page, references, attachments or appendices.

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