Electronic Blog for hobbyist

Embedded MP3 module

cxema — Fri, 28 Dec 2012 06:57:46 GMT

This embedded MP3 module is an universal and compact circuit (37 mm x 27 mm) for playing MP3 audio files. The MP3 module can be used in embedded systems.
The MP3 files (up 65,536) are stored in a micro SDcard.This embedded MP3 module is an universal and compact circuit (37 mm x 27 mm) for playing MP3 audio files. The MP3 module can be used in embedded systems.

The MP3 files (up 65,536) are stored in a micro SDcard. $CUT$

Controlling the module could be done either by buttons and digital inputs or via TTL serial interfaces.

The MP3 module (developed by Luca Pascarella info at lpsystems dot eu) is based on MP3 converter VS1011 and a PIC24 and can play up to 65,536 songs or voice messages stored in a microSD. Each track can be selected via serial lines or by using 9 buttons or switches (64 mp3 files with dip switch). If you choose the serial communication you have to use a microcontroller, using the 9 digital lines you can control the player with logic signals from stations of various kinds, such as tension-indicator lamps, relays, etc.. The module can be used to play voice messages in vending machines, telephone systems, in the car to inform the driver of the vehicle’s condition and environmental ones, in alarm systems, to assist configuration and inform about events that occurred, and in many other areas yet. The device supports micro SD with capacity up to 16 GB and can be powered with a voltage of 3.3 Vdc or 5 Vdc selectable. The module has a single in-line single-connector positioned on one side of the PCB, so you can better manage the space and mount it also in upright position.

In "Pin-to-Pin” mode is provided the use of three buttons (PLAY / STOP, VOL UP and VOL DOWN) and a 6-way DIP switch connected to the module, while "Serial” mode the serial communication is with TTL signal level. The device can also be used in "Mixed” mode that allows you to issue orders both with serial port and pin-to-pin input.
In the mode Pin-to-Pin (mode 1) to perform a song you have to select the track number using binary inputs IN1, IN2, IN3, IN4, IN5 and IN6 and then run the selected file simply giving a ground pulse on the PLAY line. Applying logical zero on the lines VOL_UP and VOL_DOWN, you can respectively increase or decrease the volume.
In serial mode (mode 0) commands are very similar to the Pin-to-Pin, except for the choice of the MP3 file, which must take place in several stages within a time limit fixed in the configuration file. The special command # allow to insert the name of the track and the second special command * and the input.
For example, to play the file 65.mp3 you must perform the following steps:
• Step 1 (mode track name) = #;
• Step 2 (first byte of the track name) = 6;
• Step 3 (second byte of the track name) = 5;
• Step 4 (mode locking of track name, optional if you wait timeout) *;
• Step 5 (Play) = P;
• Step 6 (Stop) = S.

Mixed mode (Mode 2) allows to give orders both serial and pin-to-digital input pin. In this case the number of inputs usable is 4, for a total of 16 tracks addressable with Pin-to-Pin mode.
The names of MP3 files must be a number from 0 to 65535 followed by the extension .mp3 (for example, 0.mp3, 1.mp3, 2.mp3, 3.mp3 16.mp3 … … 65535.mp3).

Schematics and BOM

Firmware download

Diagram

AD9833-based USB Function Generator

cxema — Fri, 12 Oct 2012 07:13:21 GMT

One tool that I've been missing at my lab at home is function generator. They tend to be a bit expensive, so I haven't bought one. I thought this might be a good opportunity to try and make one myself. I found a pretty common DDS (direct digital synthesis) chip, called AD9833. Then just strap a USB-enabled AVR micro there and maybe some analog electronics. $CUT$

The parts

The integral part of this design is ofcourse the DDS chip, the AD9833 by Analog Devices. The chip has a 25MHz clock input, an internal phase locked loop, a sine lookup table and an ADC. By controlling it with it's SPI interface, you can make it output sine, triangle and square waveforms at frequencies ranging from 0.01Hz to 3MHz. It goes even higher, to ~7MHz, but the sine waveform starts to look pretty awful at that high frequencies.

To control that chip, I used an Atmel at90usb162, a cheap and small USB-enabled AVR microcontroller. It's going to provide a USB virtual serial interface to the computer and it's going to interpret the commands sent over that link and change the output of the DDS appropriately.

OPA357 is going to amplify the output of the DDS a little bit. The nominal output voltage of the AD9833 is 0.6Vpp, centered on 0.3v. The OPA357 was chosen because it supported the high frequencies required and it was available from texas instruments as a free sample.

Schematic

The schematic and pcb were designed with KiCad, a pretty decent open source EDA. I'll just highlight some parts of the schematic here. The device can either be powered through the USB connection, or through a separate voltage input that gets regulated down to 5 volts. The two schottky diodes make sure the two aren't shorted together, if there's voltage coming in from both inputs.

This is the circuitry around the AD9833 DDS. The bypass capacitors and their values are directly from the datasheet, as they should be. The clock source can be selected with the JP1 to be either an onboard oscillator, or an external clock source that is fed through a BNC connector. The output from the DDS is first lowpass filtered and then amplified. There's also a 50ohm resistor to allow for 50ohm termination. I've got test points scattered throughout the whole signal path to allow for easy testing.

PCB design

The PCB layout was pretty straight-forward. Here's a screenshot of the final PCB in 3d-view of KiCad.

You can see the BNC connector for the external clock in that screenshot, that I haven't bothered soldering at least so far.

I designed the PCB to hold a surface mount oscillator, but didn't have one with the right output frequency. I did have the right oscillator in DIP package, so I just bodged it on the board like this:

A bit ugly, but works just the same.

I also had a small error in the original design. The VUSB pin of the AVR should be connected to the supply voltage, not the USB VUSB. That way, if I power the device from external power without USB, the USB peripheral can still get power and can be initialized. A simple cut trace and a solder bridge was enough to fix that.

Protocol

So the board is connected to the computer via a virtual serial USB connection. There needs to be some sort of a standard way of communicating over it. So I wrote a simple standard before I got started on any code. I decided to use ASCII to enable a human to write the commands during testing and for easier debugging and code readability.

set commands:
sf1 [freq] #in Hz
sf2 [freq] #in Hz
sp1 [phase] #in degrees
sp2 [phase] #in degrees
sfo [1/2/m(modulation)] #frequency output
spo [1/2/m(modulation)] #phase output
so [o(off)/s(sine)/t(triangle)/q(square)] #output mode
sm [freq] #modulation freq
 
All commands ending with <carriage return><newline>

So for example, to set the output frequency 1 to 100Hz, you'd send "sf1 100 \r\n".

AVR code

The USB functionality was provided by the excellent LUFA USB library for AVRs. Then I reused some code I'd written before to handle the SPI and a relatively featureful library for the AD9833. Then some code to translate the commands sent over the serial to function calls to the ad9833 library.

PC software

The software is written in Python3. I started learning it a couple of months ago and have used it to create some simple UIs so far. I used the tkinter graphical framework for the GUI and pyserial for the serial connection. The code behind the UI isn't pretty, I'm still not that comfortable with Python. It's a fine language, but I prefer working with microcontrollers and writing code in c.

The UI turned out quite nicely in the end and it works well. There's some things I'd like to do differently, though. The modulation output selections should be in their own radio button collection, for example. If I wanted to add amplitude shift keying, there's no clean place to put it to. Maybe I'll get around to doing that at some point.

The logic behind the application is very simple: the application just sends appropriate commands over the virtual serial usb port whenever any of the values change on the UI. Not much to it.

All code and PCB files here

PICLab-40 PIC Microcontroller experiment board

cxema — Tue, 10 Jul 2012 10:40:28 GMT

This is a two-in-one PIC programmer and Experiment board for 40 pin PIC Micro devices.It easy to developt your program without insert/remove PIC micro.You just programming your code and then download to this board without any programmer .This board interface with parallel port.This board supports for PIC16F,PIC18F 40 pin devices . $CUT$

Devices support

All 40 Pin devices with Flash memory such PIC16FXXX,PIC18FXXXX

For other devices see for each software that support this programmer

Donwload PCB
This is protel zipped pcband schematic.

CCS Examples
Example for test this project.

Software that support this programmer

EPICWin Support PIC12F,PIC16F and some PIC18F.Support all windows
WinPic800 Support PIC12F,PIC16F, PIC18F,dsPic (set hardware as ProPIC2) Support allwindows
ProPIC18 Support PIC18F only Support all windows

How to use with EPICWin
To use this programmer with EPICWin first you must have EPICWin software which available from Melabs.com.After you have download files then install it as description in the manual.

For windows XP/2000/NT you must install driver by :
Start --> Run ---> C:\epicwin\NTINST.EXE /install

To remove driver.
Start --> Run ---> C:\epicwin\NTINST.EXE /remove

Note : If you use Windows XP you must Stop Windows XP from polling printer port by
download the registry entry file from Melabs.com and merge it into your XP registry.After download this file to merge it into registry just duoble click on this file and select yes and OK
Download XP_stop_polling.reg

Now you can use this programmer by double click on epicwin.exe if the programmer not connected to parallel port you will have warning message "PIC Programmer. Not Found"

If you have the message "unable to start driver PICLPTNT error xx hex(xx) " when starting EPICWin this is happen becuase you not enable parallel port in BIOS. I found this problem with some model mainboard becuase it selected disable parallel port as defualt or when you have flash new version BIOS firmware.

3 digits Digital volt meter

cxema — Tue, 10 Jul 2012 10:26:18 GMT

This is simple 3-digits digital volt meter. PIC16F676 used to read analog signal(voltage) and display the value on 3-digits 7-segment. You can apply to mesasure DC currant with parallel R-shunt but I'm not descript here. $CUT$

As we know the most of PIC microcontroller has 8-bit/10-bit on-chip Analog to Digital converter module. In this project I use PIC16F676 which have ADC 10-bits 8 channel but this project use only one channel for measure voltage input for other pin set as digital I/O.

From the schematic above the input voltage divided by R1 and R2 (voltage divider).VR1 parallel with R2 use to adjust appropriate display full scale voltage.The divided input voltage will connected to AN3(RA4) which set as analog input.

RA0,RA1 and RA2 set as digital output to turn on/off the digits in scan dispay routine.

RA3 not use in this version and it was input only

RC0-RC5 and RA5 use to drives the segment of dispay(7-segment decoded by software)

This project I use CCS C compiler to programming.The main routine continually read the input voltage on RA3 and convert to 7-segment code while TIMER1 set to timer for interrupt every 5mS for scan all digit about 66Hz(only one digit turn on at every 5mS).In convert digital value to voltage routine we must scale the value with the full scale display in this project I want full scale display at 30V so the input voltage must scaled with 30 and display resolution is 29mV or 30/1023. source code and shematic available here.

Free schematic and firmware

Precision +/- 15V regulator for pre-amp or headphone amplifier

cxema — Tue, 10 Jul 2012 09:49:21 GMT

This is a precision ±15V regulator on a single side PCB. $CUT$ The circuit is based on EB-802 with design by zerosoft on www.headphoneamp.co.kr .I have replaced some components that easy to find in the market and design a new PCB that look like symmetry layout.But,you can replace the components with high quality component if you can find.

prototype the top layer of PCB I use as ground plane only and unnecessary becuase all importance PCB route is the bottom only.

Adjust VR1 and VR2 to achieve the desired voltage output (±15V at CON2).

Components

D1-D4 = 1N5822

C1-C4,C13,C14,C19,C20 = 0.1uF/63V flim capacitor

C11,C12 = 220uF/16V

C15,C16 = 47uF/35V

C5-C10 = 2200uF/25V or 35V Electrolytic capacitor (C7 and C10 may be 1000uF/25V)

L1 and L2 = 100uH

Q1 = IRF640 N-channel MOSFET

Q2 = IRF9640 P-channel MOSFET

IC1 and IC2 = NE5534 OP-Amp

D9 and D10 = LM326-5.0 Voltage reference or LM329DZ/6.9V

Transformer = 15-0-15 V ,2A

All resistors are Vishey/Dale RN-55

Regulator Project
This is pdf zipped file include bottom ,component layer

5 Tips for Using a Multimeter for Your Home Improvement Projects

cxema — Wed, 04 Jul 2012 14:08:00 GMT

If you are someone who enjoys doing your own home improvement and you are working with electronics during the process, having access to a multimeter is an absolute must. $CUT$ There are going to be instances where you will need to be able to measure voltage, ohms and continuity and without an electronic multimeter, it will be difficult to determine just what you need to do. Here are a few tips for using your multimeter to perform home improvement projects.

Understand your options – Multimeters are available in different types. These can run from the most basic to the most luxuries, which is also the most expensive. Unless you have highly advanced electronic skills and knowledge, a basic multimeter is going to be just fine and will have fewer features that you need to figure out.
Familiarize yourself with your multimeter – Take some time to examine the multimeter before you use it. When looking at the face of the design you should see three different things – dial, settings and lead ports. These should be color coded which makes it much easier to avoid mistakes when plugging in leads.
Learn the dial settings – As you look at the dial, take notice of the symbols and numbers that surround it. You should see an arrow that points to the right with a plus sign beside it. This is the setting that is used for continuity. The "V” setting is used for voltage and the setting for ohms or resistance will look like a "0” with feet.
Learn the uses of your multimeter – You can test a random electrical outlet to make sure that the multimeter is working properly. Use the "V” setting for this. Check to ensure that power is not flowing through any electronic circuits that you are testing. If you would like to test for a blown fuse, remove the fuse from the clamps and set the meter for continuity testing. Simply touch each end of the fuse with the meter’s probe and if the fuse is operating properly you should hear a beep.
Test for amperage – When testing for amperage you have to be a bit more careful. This is a more complicated process and requires that you use more than just two probes. You can use a clamp add-on for amperage testing by plugging it into two ports that read "A” and "Com.” Clamp the tester onto the hot wire that you want to test or you can simply purchase a plug that includes a wire loop specifically designed to test amperage.

Multi-purpose dual power supply (5.0V and 3.3V) regulator board

cxema — Wed, 04 Jul 2012 11:26:12 GMT

All embedded systems require electric power to operate. Most of the electronic components inside them, including the processors, can operate at a wide range of supply voltage $CUT$. For example, the operating voltage range for the PIC16F1847 microcontroller is 2 to 5.5 V. But there are certain applications where you need a regulated constant voltage to avoid malfunctioning of the circuit or getting erroneous results. For instance, any application that involves analog-to-digital conversion (ADC) requires a fixed reference voltage to provide accurate digital count for input analog signal. If the reference voltage is not stable, the ADC output is meaningless. Here is my latest dual power supply regulator board that provides constant 3.3V and 5.0V outputs from an unregulated DC input (6.5-10V). It is small in size and can be easily enclosed inside the project box along with a project circuit board. It can also be used to power test circuits on breadboard. The board uses two AMS1117 series fixed voltage regulators and receives input power through a DC wall wart or an external 9V battery.

The regulator circuit uses two AMS1117 series fixed voltage regulators, AMS117 5.0 and AMS1117 3.3, to derive constant 5.0V and 3.3V outputs from an unregulated DC input voltage. The circuit diagram of the board is shown below.

Note that both AMS1117-3.3 and AMS1117-5.0 derive input power directly from the unregulated supply voltage, which means each of them can deliver up to 1.0A of current. However, for the safety of AMS1117-3.3 regulator IC, the unregulated input voltage is recommended to be within 6.5 to 10.0 V. This board is best to use in a project that is designed tobe powered with a 9V DC from either a PP3 battery or a wall adapter. The PCB is only 1.9″ x 1.4″, and occupies a small area inside the project box.

PIC12F microcontroller project board

cxema — Wed, 04 Jul 2012 11:19:04 GMT

The 12F series of PIC microcontrollers are handy little 8-pin devices designed for small embedded applications that do not require too many I/O resources, and where small size is advantageous. $CUT$ These applications include a wide range of everyday products such as hair dryers, electric toothbrushes, rice cookers, vacuum cleaners, coffee makers, and blenders. Despite their small size, the PIC12F series microcontrollers offer interesting features including wide operating voltage, internal programmable oscillator, 4 channels of 10-bit ADC, on-board EEPROM memory, on-chip voltage reference, multiple communication peripherals (UART, SPI, and I2C), PWM, and more. The following project board is designed for fast and easy development of standalone applications using PIC12F microcontrollers. It features on-board regulated +5V power supply, header connectors to access I/O pins, ICSP header for programming, a reset circuit, and small prototyping area for placing additional components.

The picture below shows a closer view of the features on board.

Two-pin terminal block for DC input (6-12V DC)
AMS1117-5.0V regulator
PIC12F microcontroller on a DIP IC socket
Tact switch connected to RA3 I/O pin, which is input only. It can be used to reset the microcontroller if MCLR is enabled. Otherwise, it can be used as an user input switch.
Header connector for ICSP programming using chipKIT2/3.
Headers to access I/O pins and power supply pins (Vcc = +5V). Note that RA5 has been mislabeled as RP5 on silkscreen.
Small prototyping area for connecting additional circuit. The regulated +5V power supply for the additional circuit can be derived from the Vcc header pins.

Important: The RA0-RA5 names are used for I/O pins of the PIC12F micrcontrollers in the enhanced mid-range family (PIC12F1822, PIC12F1840, etc). The corresponding I/O pins for the old ones (PIC12F629, PIC12F675, PIC12F683, etc) are named as GP0-GP5, and have the same pin configurations. Therefore, this board can be used for both.

LT8610 – 42V, 2.5A Synchronous Step-Down Regulator

cxema — Sun, 01 Jul 2012 17:21:09 GMT

The LT8610 and LT8611 are 2.5A, 42V input capable synchronous step-down switching regulators. Synchronous rectification $CUT$ delivers efficiency as high as 96% while Burst Mode operation keeps quiescent current under 2.5µA in no-load standby conditions. A 3.4V to 42V input voltage range makes the parts ideal for automotive and industrial applications.

Internal 3.5A switches can deliver up to 2.5A of continuous output current to voltages as low as 0.97V. The LT8611 includes all of the features of the LT8610, plus a built-in current sense amplifier with monitor and control pins, enabling accurate input or output current regulation and limiting.

LT8610 – 42V, 2.5A Synchronous Step-Down Regulator - [Link]

LTC3605A – 20V, 5A Synchronous Step-Down Regulator

cxema — Sun, 01 Jul 2012 17:15:37 GMT

The LTC®3605A is a high efficiency, monolithic synchronous buck regulator using a phase lockable controlled on-time constant frequency, current mode architecture. $CUT$

PolyPhase operation allows multiple LTC3605A regulators to run out of phase while using minimal input and output capacitance. The operating supply voltage range is from 20V down to 4V, making it suitable for dual, triple or quadruple lithium-ion battery inputs as well as point of load power supply applications from a 12V or 5V rail.

LTC3605A – 20V, 5A Synchronous Step-Down Regulator - [Link]