SD Card Data Logger

Senior Design II

Final Presentation

April 21, 2011

TEAM

Team Advisor:

Dr. Patrick Donohoe

James Felkins (EE) Team Leader, Web Design,

Test Board

Harry Corey (EE)

Test Cases, Hardware Design, Part Procurement

Brendan Babiak (EE)

Prototype Construction, Buffering Scheme, MDDFS

Jaron Martin (CPE)

Command Set, SPI/UART Input, MDDFS

OUTLINEIntroduction to Project• problem/solution• tech./practical constraints

System Overview• high-level system design• software solutions

Hardware Design• power• PCB

Testing• subsystems• features

Questions

WHAT IS THE S-DRIVE?

The S-Drive is an OEM module that accepts data through a serial connection and saves it to an SD card.

THE PROBLEM

SD cards are a viable storage medium with unique advantages but involve complex overhead.

SOLUTION

The S-Drive will handle the unwanted overhead and make SD cards a more desirable solution.

TECHNICAL CONSTRAINTS

Name Description

Communication The device uses UART and SPI data connections.

VoltageThe device supports an input voltage between 3.3 or 5 V.

Current DrawThe device draws a maximum current of 250 mA in active mode and less than 10 uA in sleep mode.

Storage MediumThe device interfaces with a standard size, 32 x 24 x 2.1 mm SD card.

Memory The device supports all SD cards up to 32 GB.

PRACTICAL CONSTRAINTS -

ECONOMICThe device must cost less than $60.

Competitor Price

VDRIVE2 $24.50 [4]

Logomatic v2 $59.95 [3]

Avisaro M20511 99.00 € (~$133) [2]

[2]

[4][3]

PRACTICAL CONSTRAINTS - MANUFACTURABILITYThe device must easily fit and integrate into other systems.

•Provided on a PCB

•No larger than 5 in2

•Easily mountable

SYSTEM OVERVIEW

SYSTEM OVERVIEWSoftware Implementation

-Microchip’s MDDFS library

-Command Interface

SYSTEM OVERVIEWSize constraint met

SYSTEM OVERVIEWCommand Set

Open File for Append

1      Opens the file LOG1.TXT for appending. Only use if no file is currently open. Returns 1 if successful, else returns error code. Creates the file if it does not exist.

a  

       

Open File for Read

1 2 - ?    File name followed by \n character to represent the end of the name. File pointer will start at the beginning of the file. Use only if no file is currently open. Returns 1 after each byte if OK, else returns error code.

o File Name  

       

Close File

1       Closes the file so that another file can be opened or the SD Card can be safely removed. Use only if a file is open in either write or read mode. Returns 1 if successful, else returns error code.

c  

       

Write Data1 2 3 - [4-257]   The S-Drive will append the next NumBytes received to the end of the file. Use only

if the file is opened in write mode. Returns 1 after each byte if OK, else returns error code.w # of Bytes Data  

       

Read Data

1      Each time the r command is is received, the next byte in the file is returned and the file pointer moves one by byte. Use only if the file is opened in read mode. Returns the next byte in the file. If at EOF, starts over at beginning of file.

r  

       

Move Read Pointer

1 2    Moves the read pointer NumBytes without replying with each byte of data. Use only if file is open in read mode. Returns 1 if sucessful, else returns error code.m # of Bytes

 

       

Flush Buffer

1       Flushes the write buffer. Use to flush the buffer if you do not want to wait for the buffer to automatically get written. Use only if file is open in write mode. Returns 1 if successful, else returns error code.

f  

       

Sleep1      

Forces the S-Drive to enter sleep mode.s         

Big File1 2 - ? ? Allows for long or unknown lengths of data to be written to SD card. Use only if the

file is opened in write mode. Returns 1 after each byte if OK, else returns error code. End this command by sending a NULL byte.

b Data NULL

SENDING LARGE FILES

Data size not pre-specified•Binary files may contain all possible byte values•Toggle wake pin to signal EOF

INTERFACE MODESSPI & UART

•multiple baud rates•config.txt file•jumper determines mode

BUFFERING SCHEMEFlow Control

•2.3 kB each buffer•READY pin

WHILE INACTIVEEnters ‘Sleep Mode’

•Enters mode via SLEEP command•Dedicated WAKE signal•Uses READY pin while re-initializing SD card

HARDWARE DESIGN & TESTING

HARDWARE INTERFACE

8 wires•UART/SPI TX & RX use same lines

SCHEMATIC

SD CARD SOCKETStandard-sized SD cards

•Supports adapters for mini- and micro- SD cards

POWER SUPPLYAccepts 3.3 and 5 V inputs

•Power mode determined by jumper•5 V mode uses a low-dropout LR

POWER SUPPLYCurrent draw

•SD card has own power rail•SD card is uses ~250uA while inactive•Sleep mode cuts power to SD card•Implemented with a low-dropout LR

POWER AND CURRENT DRAW (SPI)

Power (V) Inactive Current Draw (mA)

Active Current Draw (mA)

Sleep Current Draw (uA)

Constraint Met?

3.3 19.2 68 4.60 Yes

5 19.4 73 69.5 N/A

POWER AND CURRENT DRAW (UART)

Baud Rate Power(V) Inactive Current Draw (mA)

Sleep Current Draw (uA)

28800

3.3 18.6 8.8

5 18.7 74.0

57600

3.3 18.6 8.9

5 18.7 74.1

115200

3.3 18.6 8.9

5 18.7 74.1

PCBPractical Constraints

•Small•Affordable parts•Mountable

PCBIssues

•Disjoint ground planes•SPI buses fused•Issues corrected for web-site

SYSTEM TESTING

TEST-BOARD

SUBSYSTEMS– SPISPI Master SPI Slave

Logic Analyzer

SUBSYSTEMS– UART

Logic Analyzer

Realterm

FULL SYSTEM TESTING

Operational modes• 8 possible combo’s

TESTING - GUI

TESTING - GUIPython Tool

• Handles semantics• Very slow• Used to test robustness• Better demo

TESTING – LARGE FILESReading large file from SD card

• Took appx. 1 hour w/ Python tool for 20kB• File perfectly copied• Testing done in all modes• ~3.5 kbps reading and writing

TESTING – LARGE FILES

TESTING – REAL THRU PUT

Sending/Receiving a large file:• Intermediate MCU sends 5 million chars• Data rate ~15kB/s

TESTING – COMMAND SYNTAX

Command Functions• All functions do their job• Improper commands are ignored (no crash)

PRODUCT COST

FINAL PRODUCT PERFORMANCE

Issue Constraint Actual Spec Met?

Comm. Interface UART & SPI UART & SPI

Voltage 3.3 & 5 (V) 3.3 & 5 (V)

Current Draw <10 uA (sleep) ~4.5 uA

Storage Medium Standard SD Standard SD

SD Card Size Up to 32 GB Up to 32 GB

REFERENCES[7] Microchip, “PIC24F Family Reference Manual, Sect. 21 UART,” Microchip Technology Inc., January 26, 2010. [Online] . Available: http://ww1.microchip.com/downloads/en/DeviceDoc/en026583.pdf. [Accessed September 14, 2010].

[8] Microchip, “PIC24F Family Reference Manual, Sect. 23 Serial Peripheral Interface (SPI),” Microchip Technology Inc., March 22, 2007. [Online] . Available:http://ww1.microchip.com/downloads/en/DeviceDoc/39699b.pdf. [Accessed September 14, 2010].

[9] STEC, “SLDSxxxBS(I)U Data Sheet,” STEC Inc., March 2008. [Online] . Available: http://www.stec-inc.com/downloads/flash_datasheets/SLSDxxxB_I_U61000-05203.pdf. [Accessed September 14, 2010].

[10] Sparkfun Electronics, “Logomatic v2 Serial SD Datalogger,” On-Line Store,2010.[Online].Available:http://www.sparkfun.com/commerce/product_info.php?products_id=8627. [Accessed:September 14, 2010].

[11] C-ONE Technology Corp., “Wide Temperature Industrial SD Card Product Specification,” May 2010. [Online]. Available: http://www.psism.com/c-1sd.pdf. [Accessed: September 14, 2010].

 

QUESTIONS?