Saturday, May 22, 2010

PIC18F SD WAV Audio Player

As inspired by Simple SD Audio Player by ChaN, this project uses Microchip's PIC18F2550 to read RIFF WAVE files, and display some file information on the N6610 LCD; And then it will play the audio itself through PIC's PWM with a simple RC filter on the output pin. The hardware actually comes from my previous project, and I just attached a ready-made audio amp (w/ speaker) for the demo.
Due to PIC's peripheral limitations, I only set the PWM frequency to 187.5kHz and not the 250kHz carrier frequency originally used by ChaN, because it's the maximum PWM frequency than can still get an 8-bit resolution of the duty cycles (=48MHz/256). It is also possible to use R-2R ladder in stead of (low-pass) filtering the PWM output since there still enough unused digital output pins for this approach.
On the software part, I wasn't able to make a good data buffering as good as what ChaN did. It's noticeable with WAVE files with higher bit-rates (=SampleRate*NumChannels*BitsPerSample). Nevertheless, it can still support up to 48kHz sampling rate, but with only Mono channel and 8-bits/sample resolution.

demo video:

Source code(PICC-18) with and without LCD: PIC18 SD WAV Audio Player

My on-going project: currently porting the code to STM32F103RB for additional features.

Some useful software (shareware) tools:
TextAloud - Text to Speech software
Switch Sound File Converter-multi format audio file converters

Tuesday, May 11, 2010


It is similar to my first PIC SD BMP Reader , and almost the same circuit except for the LCD. This time I now use a Nokia 6610 LCD. The LCD is capable of displaying 4096 colors, but for code simplicity I just operate it at 8-bit (256 colors) resolution.

This project is capable of reading bitmap file using common format (24-bit per pixel), with size (width and height) equal to or less than 132 pixels at both side.

demo video:

Source code + diagram: PIC18 SD BMP Reader 2.rar

similar project at Hack-a-day: How-to: Digital picture frame, 100% DIY
-it uses PIC24FJ64 in stead of pic18f2550

Saturday, May 8, 2010

PIC18 SD BMP Reader

This project uses Microchip's PIC18F2550 and Nokia 3310 LCD to read and display images from BMP files on the SD/MMC cards. Although the display itself is monochrome, it still supports 24-bpp (bits per pixel), 8-bpp, 4-bpp, and 1-bpp (monochrome) Bitmap files (*.BMP) with size of 84x48 pixels. It uses the Petit FAT File System Module by ChaN.

Diagram and simulation:
Actual circuit:

Demo video:

forum link: Petit FAT File System (w/ Proteus ISIS simulation)

Source code(PICC18) + simulation(ISIS) + others: PIC18 SD BMP Reader.rar

references for BMP file format:
Wiki BMP file format
atlc.sourceforge bmp format
MSDN Types of Bitmaps