Dilshan R Jayakody’s Web Log

This project is about 24-bit stereo DAC, which we build for Raspberry Pi boards. This R-2R ladder DAC is developing around Intel / Altera EPM240T100C5N CPLD. We developed this module after review the PT8211 DAC, which we tested a few months ago. Compare with PT8211 DAC, this module is capable to provide high-quality audio output with Raspbian OS . A finished prototype of the R-2R DAC. At the testing stages, we drive this DAC with the I 2 S bus of the Raspberry Pi 3 Model B board . The provided device tree overlay is developed and tested on the new Raspbian Buster OS. The audio quality of this DAC is impressive. In most of the circumstances, we test this unit using mpg123 player and got excellent results. The MCP602 opamp of this module is capable to drive a headphone, and for the testing, we use Audio Technica ATH-PRO500MK2BK headphones directly with this module. Also, we pair this module with several AF power amplifiers and obtained superior results. The most n...

In the last couple of years, I tried several powered USB hubs to drive some development boards and USB peripherals. Most of the USB hubs which we can find in the local market are unreliable or not designed to drive more than 500mA of a load. After having a few bad experiences with powered USB hubs, I decided to build a USB hub by myself. I specifically design this hub to drive USB powered development boards and experimental peripherals. The core element of this USB hub is the " FE1.1s " USB 2.0 hub controller. " FE1.1s " is a low cost, 4-port, high-speed USB hub controller, and this chip can easily order by eBay or AliExpress . A prototype version of the USB hub. Apart from FE1.1s features, this USB hub has the following additional features: Switches to on/off and reset individual USB ports. Capability to provide a maximum of 3A of current from each USB port. Power using 9V to 15V DC voltage source. This USB hub uses PIC16F630 MCU and four units...

When purchasing SLT ( Sri Lanka Telecom ) PeoTV connection, we are getting a  preconfigured ADSL router and STB. Generally, the router they provided is a 4-port, low-cost ADSL router. The unit which I received with my PeoTV connection is " PROLiNK H5004NK ", and it is a decent quality 4-port ADSL router with a WiFi transceiver. I used this router for one year, and the main issues I noticed with this router are its unnecessary resets during heavy network traffic and limit configuration options. Due to the recent upgrade of my network, I replaced this router with the TP-Link W8961ND router. TP-Link W8961ND bundles with ADSL 2/2+ Modem, 300Mbps WiFi access point, and 4-port router. TP-Link W8961ND Router I purchased this router from a computer component seller and NOT from SLT. As usual, this router arrives with the default configuration, and I managed to configure it for SLT ADSL and PeoTV without any problems. The firmware version of this router is version 3.0...

This tuner circuit is a quick prototype which I build to test the RDA5807M FM radio tuner IC. RDA5807M is a single-chip tuner IC with RDS and MPX decoder, and it equipped with I 2 C interface for control. The main reason to build this prototype is to understand the behavior of this chip. The prototype version of the RDA5807M receiver. At the time of this design, the website of the RDA microelectronics is not accessible from my location. Because of this reason, I download different versions of RDA5807M datasheets from the internet. While going-through those datasheets, I observed that it comes with limited information. Finally, I decided to build this receiver to verify some of those parameters and to review the RDS functionality of the chip. I build this receiver around ATmega16A MCU. I choose this MCU because I got a few of ATmega16A MCUs in my inventory and also due to the higher number of  I/O pin count. RDA5807M module. In this design, the volume is contro...

USB Morse Keyer is a microcontroller-based auto keyer project with following features: USB / straight key / iambic key inputs. Support for both standalone and USB operating modes. 64-character USB typeahead buffer and 6-character Morse key typeahead buffer. Support 5, 10, 15 WPM. 6-page message memory. 1W Audio output. Audio and PTT output interfaces. 32 character display  Final view of the USB auto keyer. The USB interface of this unit is designed to work with most of the operating systems. It emulates a virtual serial terminal to transfer keystrokes to the keyer. In most of the operating systems, this interface works without installing any additional device drivers. To submit keystrokes user can use any serial terminal software such as PuTTY , Hyper Terminal , Minicom , etc. This keyer is designed to work with 7V to 16V DC input voltage. The most recommended working voltage is 9V. The bottom side of the USB auto keyer. To reduce the dimension of the P...

This quick post is about the verification script which I did to test the PT8211 DAC functionality. This script is designed to work with Arduino boards and, I tested with Arduino Due and Arduino Mega 2560 boards. The script is self-explanatory, and it emulates the I2S interface and communicates with the PT8211 DAC. The output waveform of PT8211 on Arduino Due board. With this script, PT8211 generate sine wave in both channels. The frequency of the waveform is dependent on the clock frequency of the Arduino board. In Due board, PT8211 generates 0.052kHz sine wave on both channels. Connections between PT8211 and Arduino. The test setup is quite straightforward. I2S and power pins of PT8211 need to connect to the Arduino board in the following order: Serial clock ( BCK ) - Pin 22 Channel selector ( WS ) - Pin 23 Data ( DIN ) - Pin 24 VCC - 5V (Mega 2560 board) 3.3V (Due board) GND - GND Left and right channels of the DAC is connected to oscilloscope or frequenc...

A few years back I purchased Honeywell CL15AE evaporative air cooler and it is15L indoor air cooler manufactured by JMATEK (for Honeywell). Sine last week this cooler became dead, and the only thing which I can see live is its red color power indicator. After disassembling the unit I see that most of the components of the controller PCB are rusted and damaged.  As I observed the main reason for corrosion is the absence of protective varnish on the top side of the PCB. The original control board of CL15AE cooler. At first, I restore all the damaged parts in the PCB with new parts, which including SS8050 , SS8550 , transistors and a few of electrolytic capacitors. After replacing those components, the unit starts to beep during power up but failed to power on. Damaged SS8050 and SS8550 transistors. After some tests, I figured out the problem is in SONiX SN8P2602 8-bit microcontroller.  Due to unavailability of microcontroller and it's firmware I decided to pr...