Bush WI-1810 Internet Radio - Quick Teardown and Analysis

The Bush WI-1810 is a budget internet radio and Bluetooth speaker sold by Argos. At the time of writing, it was discounted to £25, but at its usual price of £49.99 it still represents the low end of the internet radio market. The radio is based on the Magic Systech platform, which is a popular platform and is found on many internet radios, but more premium brands such as Roberts and Pure use the competing Frontier Silicon SmartRadio platform. Both platforms allow set designers to incorporate a variety of features in a set including but not limited to internet radio, Bluetooth, uPnP streaming, FM, DAB+, CD player, and line in, but this set analysed here only features the first three of those features.

The current consumption of the radio is 0.25A @ 6.0V when in standby and 0.3A when on but nothing is playing. The current goes up by a negligible amount when an internet radio station is playing and the volume is turned down. When the volume is turned up to maximum, the current varies according to the audio and peaks at around 0.5A.

The level of integration in this product is surprisingly low. My original expectation was that there would be a Magic Systech-branded chip inside performing most of the key functions of the radio, much like the Frontier Silicon radios, but all of these functions are carried out by independent ICs and the CPU is an off-the-shelf one not specifically designed for radios. Despite the complexity of the design, components have been carefully selected to lower the cost whilst still delivering a reasonable level of performance where it matters - the audio quality.

Electrolytic capacitors - all off-brand through-hole 10V types, but surprisingly rated for 105 degrees C. Through-hole electrolytic capacitors are still cheaper than surface mount ones for some reason, so the extra assembly effort is often worth it.

CHMC SBE SCA108 Voltage regulator - I couldn't find anything for this part number, but the 0.33R resistor between pins 6 and 7 and the connections to the inductor, schottky diode and timing capacitor point to this being a really cheap Chinese clone of the MC34063, which itself is the cheapest widely available Western switching regulator IC. The 51k and 33k feedback resistors give an output voltage of 3.18V. This IC has a rather high maximum input voltage so this should give good headroom against overvoltage on the input.

The MC34063 is generally a good choice for this application. The only real disadvantage it has is that its switching frequency is low, which means it needs a fairly high-value inductor (typically 220uH), which is physically quite large at the regulator's typical rated current of 0.5A. Large inductors are expensive, so the designer has used a rather small inductor here.

I don't know how much current this design uses at 3.3V, or the current rating of the inductor, so I can't comment on whether it is comfortably adequate or being stressed. However, as both the inductor and chip get rather warm when the set is running, and the set uses 0.3A @ 6V when it's not producing any sound and it runs Linux, I would guess that the current it uses at 3.3V is much closer to 500mA than it is to 0mA, so if the device fails, I would check this inductor.

Nuvoton N32905U3DN main CPU - a surprisingly exotic chip which can run Linux and drive LCDs up to 1024x768. I found some limited information elsewhere on the internet which indicates that the Magic Systech software platform is Linux-based and that it is not exclusive to Nuvoton CPUs. The chip itself is not very old but the ARM926EJ-S CPU core itself is rather dated, which probably keeps costs down and contributes to the general sluggishness of the user interface.

W25Q32JV flash - this 32Mbit capacity (4Mbyte) flash chip will contain the entire program of the product as the CPU does not have any significant program memory of its own.

Super Chip SC2314 audio processor - this applies effects like volume, balance, bass, treble, etc. I'm surprised they didn't integrate these functions into the main CPU and implement them in software. Both channels appear to be in use, so there's an opportunity to mod in a stereo headphone jack to replace the mono jack it comes with. The L and R outputs from this chip go to C15 and C14, the other ends of which are connected together. I haven't tested it to see if the channels are stereo before that point.

CS8509E - Class D amplifier. Rated for operation up to 9.2V, and can deliver up to 8.5W into a 4-ohm load at 8.5V or 3W into a 4-ohm load at 5V. When powered from 6V, the maximum power would only be just over 3W at 1% THD according to a graph in the Chinese-language datasheet, which is probably why the Argos listing says it only has an output power of 3W despite the speaker being rated for 5W.

MT7601 Wi-Fi chip - commonly found in cheap Wi-Fi dongles, and probably selected for availability of Linux drivers. There is no Ethernet port on this set, which keeps the price down, but can result in reception being wiped out if the microwave is used in the kitchen (a common location to deploy a radio like this).

Bluetooth receiver - Beken BK8000 (under the sticker). This chip is commonly used on those Bluetooth-to-3.5mm modules which can be found on Aliexpress for next to nothing. Some of those Aliexpress modules look identical to the module in this radio. The module features a flash chip with a quarter of the capacity of the main processor's flash chip! All the audio decoding is done inside the BK8000, so the main processor just drives the module with some GPIO and presumably routes the audio to the speaker via the SC2314.

Speaker - 5W. This rather hefty speaker is not hi-fi quality but it's much better than that which would typically be found in an entry-level DAB/FM radio or even some entry-level boomboxes and the sound quality is quite reasonable for such a cheap set. I don't have a proper sound level meter so I can only give approximations of the frequency range, but when connected to a phone running a signal generator app via Bluetooth, the volume started to drop off below 80Hz and nothing was heard below 50Hz. At the high end, it sounded fine up to at least 9kHz.

Experimenting with RF modulators part 2: Sky IO Link and control via a Raspberry Pi

Following on from Experimenting with a programmable RF Modulator (making a controller for it and testing harmonics), I have continued my work on this topic with these goals in mind:

• Make a neater VBIT-Pi assembly by integrating the modulator, VBIT-Pi hat and Raspberry Pi into a single unit
• Control a Sky IO Link

Raspberry Pi control

The Raspberry Pi already has I2C support, and it is fairly straightforward to use it from the command line and in a Python script. In my application, the Raspberry Pi is already being used with a VBIT-Pi hat, an open-source hardware teletext generator which adds teletext data to an external video signal, which has two ICs on it connected to the I2C bus. Fortunately, the modulator IC's I2C address is different to the two ICs, so it's simply a case of wiring up the I2C pins to the same pins used on the VBIT-Pi.

The i2cdetect command can be used to test that all the I2C devices are connected:

pi@raspberrypi:~ $ i2cdetect 1
WARNING! This program can confuse your I2C bus, cause data loss and worse!
I will probe file /dev/i2c-1.
I will probe address range 0x03-0x77.
Continue? [Y/n]
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- 25 -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- 44 -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- 65 -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

The modulator can then be tested from the command line with a command like this: i2cset -y 1 0x65 0x80 0x10 0x25 0xF4 i (this will set the output to C21)

I modified the VBIT-Pi to remove the composite video output, since that was now wired into the modulator, and add an audio input for the modulator instead. I also added a micro USB port (wired to a GPIO pin via a resistive divider) with the intention of connecting that to the USB port on the set top box that will supply the video signal, so that the modulator is only active when the set top box is on.

I wrote the script to control it in Python. To keep things simple, I only implemented the maths for UHF channels, even though the modulator supports VHF channels.

When pressed into service, the Pi can be set up to run the script at startup. During testing, it can be started from the command line with python3 ./rf-mod.py and terminated with Ctrl+C. If you have no need for the external enable, then all the code concerning the GPIO interrupt can be removed.

# RF modulator example code
# This example controls an MC44BS373CA RF modulator
# from a Raspberry Pi. The GPIO set as an input
# can be used to enable and disable the RF modulator
# on demand, and if connected to the USB port on a
# set top box, will automatically turn the modulator
# on when the set top box is on.

import time

import smbus
# Set I2C bus number (may vary according to the Pi used)
bus = smbus.SMBus(0)

import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)

# GPIO 23 set up as input.
GPIO.setup(23, GPIO.IN)

device_address = 0x65
# Set desired channel here (UHF only)
desired_channel = 38
# Set to 1 to enable test pattern or 0 for normal behaviour
test_screen_enable = 0
desired_frequency = (desired_channel - 21) * 4 * 8 + 1885
desired_n = (desired_frequency << 2) & 0x3ffc
desired_n_h = (desired_n >> 8) | (test_screen_enable << 6)
desired_n_l = desired_n & 0xff
config_values = [0x80, 0x10, desired_n_h, desired_n_l]

def configureModulator(gpioChannel):
        #gpioChannel only needed for setting up event handler; it doesn't do anything
        try:
                time.sleep(1)
                bus.write_i2c_block_data(device_address, config_values[0], config_values[1:4])
                print("RF Modulator configured: C", desired_channel, " System I")
        except:
                print("I2C Bus Error (Modulator probably not powered)")

#Configure now just in case modulator is already powered
configureModulator(0)

try:
        GPIO.add_event_detect(23, GPIO.RISING, callback=configureModulator, bouncetime=2000)
except KeyboardInterrupt:
        GPIO.cleanup()       # clean up GPIO on CTRL+C exit

#Loop forever - should not be resource intensive
while True:
        time.sleep(1000)

GPIO.cleanup()           # clean up GPIO on normal exit

This works very well and reliably. The output of the modulator is fed into the house AV distribution system, making it available at every TV point in the house. In retrospect, it may be more useful to use the set top box signal to control a multiplexer which switches the video input between the set top box and Raspberry Pi's composite video out, instead of turning the modulator off. The Pi could then be used to display an "in vision" service or other video content when the set top box is turned off.

Sky IO Link

The Sky IO Link is an RF modulator in a small box which was introduced alongside later Sky+HD boxes where the built-in modulator was removed to reduce costs. This modulator is still made today (2022) by various manufacturers and sold at a low price (~£10), which makes it a great choice for any project requiring a modulator.

The modulator is similar to the ones that were previously built into the Sky boxes, but with an Abilis modulator IC rather than the Freescale one used previously, but the IC claims to be a drop-in replacement, so it should work with the code I've already developed.

The short cable is terminated with a 10-way mini DIN connector, and probing around suggests the following pinout: (wire colours on my unit shown)

The VBIT-Pi's open-source PCB layout could be modified to include the mating connector, which would allow neat and tidy integration with the Pi.

For testing, I wired the connector up to the Pi's GPIO header and connected the video input to the Pi's video output:

• 4 (Power supply) - 2 (5V)
• 5 (GND) - 9 (GND)
• 6 (SCL) - 5 (GPIO 1 / SCL 0)
• 7 (SDA) - 3 (GPIO 0 / SDA 0)

The SCL and SDA pins require pull-up resistors, and should be pulled up to 3.3V (not 5V as shown in my photo, but I got away with that bodge).

I ran my Python script from earlier (changing the SMBUS port to 0 for the original Pi in use here) and it worked perfectly.

Outdoor LED lighting controller

Introduction

This is a simple project which is a lighting controller for the inexpensive LED tape which is widely available from marketplace sites and is designed to be powered from 12V.

The requirements for this project were:

• Automatically turn the LEDs on at dusk and turn them off at dawn
• Run the LEDs at a dim brightness during normal operation, or at high brightness when high brightness mode is enabled
• Have a button for selecting high brightness mode. High brightness mode shall automatically be turned off after a time period
• Have good efficiency

Preliminary testing

Prior to building the controller, the waterproof LED tape was installed as desired around the outside of my house. Around 8 metres of LED tape was installed in three separate lengths and mains flex was wired between each of the three runs and a central location where the controller will be installed along with its light sensor.

The LED tapes were all connected to a bench power supply in parallel for testing.

At the design voltage of 12V, the LEDs are at full brightness and consume around 2A of current for a total of 24W of power. The LEDs are quite bright at this power and the brightness is far too excessive to be used all night, not to mention the high operating costs over the long term.

The voltage was turned down until a sensible brightness for all-night operation was found. This was found to be in the range of 7.90V to 8.10V, with the current varying from 0.05A to 0.10A, and the power from 0.395W to 0.810W. With this in mind, a target voltage of 8.00V was chosen, which should result in a power consumption of only 0.6W (plus overheads from the mains power supply), resulting in low running costs.

Design

The power section of the design was be based around one of the inexpensive and widely available LM2576 buck converter boards. The board was modified to replace the trimmer potentiometer with fixed resistors to avoid future unreliability, and the Enable pin was carefully desoldered from the PCB so that it could be externally driven. A connection was also added to the feedback junction so that an extra resistor could be wired in parallel with the main resistor; this would form the basis of the brightness selection, where this resistor can be left floating or shorted to GND via a transistor to modify the lower resistance value in the feedback network and hence change the output voltage of the buck converter.

Originally I planned to use a comparator wired as a schmitt trigger to control the Enable pin and a 555 timer in monostable mode to control the high brightness mode, but I decided to change to a microcontroller to allow more flexibility and make it easy to implement multiple time-out periods for the high brightness mode which can be stepped through by pressing the button repeatedly. I used a PICAXE-08M (educational microcontroller) since I already had a few, but a bare PIC or ATtiny would also work well.

Hardware

I built most of the circuit on stripboard and placed all the components to allow it to fit inside a plastic case.

Some extra resistors have been used in the feedback network compared to the schematic to trim the output voltage more accurately. Polyfuses were also added to each of the three outputs to provide independent short-circuit protection for each channel, which I thought would be a good idea given that the lights are outside.

The case was screwed to the wall and the LDR was positioned where it could be illuminated by light from outside without being illuminated by very much from the lighting it controls, and it works very well.

Wireless temperature display with bare glass LCDs

First completed: 2018

Introduction

I had previously developed a simple wireless temperature display system using a network of battery-powered transmitters which transmit the temperature from their current location using low-cost 433MHz AM transmitters spread around the house to a custom-made display unit. I wanted to add a second display to show the temperatures from the same transmitters in another location, and also wanted to take the opportunity to experiment with the LCD drivers that are built into selected Cypress PSoC microcontrollers.

The PSoC 4 is a microcontroller based around the ARM Cortex-M0 processor core which features a comprehensive range of built-in peripherals and a small amount of programmable logic.

The LCD

The DGL-0401YG-4EH LCD was included in the Kemo Electronic S043 "lucky bag" of surplus displays and likely originated as a heating controller display. Such a supply method would be completely inappropriate for a commercial product due to no guarantee of supply, but for a hobby project it's fine.

the LCD has 4 common pins and 12 segment pins, meaning it is designed for 1/4 duty cycle multiplexed operation. The waveforms for multiplexing an LCD are more complex than for multiplexing LED displays because intermediate voltages are required and DC bias must be eliminated to avoid long-term damage to the LCD, so they're usually generated using a dedicated driver IC or by an LCD driver peripheral built into certain microcontrollers.

The PSoC's LCD driver is capable of up to 1/8 duty or 1/16 duty depending on the part chosen, so driving this LCD is no problem. In theory, multiple 1/4 duty LCDs could be wired for 1/8 or 1/16 duty to save I/O compared to using 1/4 duty, but there's a catch! The lower the duty (higher the denominator), the smaller the viewing angle becomes, which means that the LCD only has good contrast over a smaller range of viewing positions.

Ultimately, due to the amount of I/O available on the CY8CKIT-042, 1/8 duty was chosen as a good compromise between the viewing angle and number of I/O used. Some of the heating-related symbols were unused, so not all of the segments needed to be connected either. The segment lines for the °C symbol could also be commoned to save a further I/O line as there would be no need to control these symbols individually.

The one button added to the front switches the backlight brightness between three levels.

Wireless communications

The 433MHz transmission system is a very simple system which does not define a protocol and is unidirectional, which means an unlimited amount of receivers can be added without any changes needing to be made to the firmware in the transmitters. The task of decoding and receiving the data was passed off to an NKM2401 to save time and due to reasons relating to the design of the temperature transmitters which was done previously, but it wouldn't be difficult to implement this directly in the PSoC. For debugging, the 3.5mm jack in the bottom left corner can be connected to a computer serial port with a PICAXE programming cable and serves the dual purpose of allowing the monitoring of the received packets and the generation of test packets.

The data is transmitted in 8 byte packets. The first byte represents the ID of the temperature transmitter and is unique to each transmitter; the display unit uses this ID to decide which of the four LCDs should be updated with the newly received temperature. The second byte represents the type, allowing for future expansion with types other than temperature (e.g. humidity). Bytes 3 and 4 contain the temperature, bytes 5 to 7 are unused/reserved, and byte 8 is a very simple checksum which augments the error detection already implemented in the NKM2401.

Animated dot matrix display radio-controlled clock

First completed: May 2013

Introduction

This project was my first attempt at driving a dot-matrix LED display from a microcontroller without using any dedicated driver chips. It was also, at the time, my most advanced PCB design. Prior to this project, the most complex LED multiplexing I had done directly from a microcontroller was a 6-digit 7-segment display, which in terms of complexity is equivalent to a single 8x6 LED dot matrix.

I decided to use an ATmega328p pre-programmed with the Arduino bootloader for this project.

Hardware

The main elements of the design are the microcontroller with its supporting components, the displays with their shift registers (these are hidden behind the displays on the PCB), and a switching regulator.

The schematic below shows the design excluding the switching regulator.

The shift registers are a serial-in-parallel-out type, and were needed because the ATmega328p does not have enough pins to drive the display directly. The shift registers are 74HC164, as with the Noughts and Crosses game.

The PCB layout was done by me, but the board itself was made by a third party. The PCB was made on a PCB router and the board is not through-hole plated - I learned a very important lesson here as to why through-hole plating is usually important. The design relied on through-hole connections being connected to both sides, so it was necessary to solder some of the pins on both sides to simulate through-hole plating.

Software

The LED displays are multiplexed. Only one row of the display is lit at a time; each row is switched on in turn very rapidly, and this technique relies on persistence of vision to make it look like the entire display is continuously lit.

The animation below shows the technique in action but for column scanning.

Initially, the software was a simple design which just used delays in the main loop of the code to switch between the rows. This method works reasonably well on the ATmega328p at 16MHz because it can execute instructions fast enough to avoid functions in the main code from having a visible effect on the display, but it makes writing the code more difficult because delays and "slow" commands cannot be used. The software design was later enhanced by using a timer interrupt to run the display software, making its timing independent of what happens in the main code.

The display shows the time, and a scrolling effect is used whenever a digit changes. The time is synchronised using a "Time from NPL" receiver, the signal from which is decoded by the software. The use of the timer interrupt for driving the display, the author's extra experience with using the ATmega328p, and the removal of the external RTC allowed the time decoding to be done without the extra microcontroller that was used in the 6-inch jumbo radio-controlled LED clock/timer project.

Noughts and Crosses Game

First completed: 2011

Introduction

This is a simple electronic game that I made as part of my Art & Design GCSE at school back in 2010/11. The Art & Design GCSE allows creations made from non-traditional materials, and they can even be electronic, as long as they are arty in some way. This project was inspired by Damien Hirst's spot paintings, and uses LEDs to illuminate each of the "spots" a different colour to represent each player.

Pressing the New Game button will start the game. The colour of the player who goes first is random. The game is purely multiplayer and has no AI. Each player takes it in turns to select their spots, and the game ends once the board is full or there are three spots of the same colour in a row.

Construction

The game is constructed on a single-layer board made on the school's simple PCB production facilities - the board was exposed to UV, etched in a tank, and hand-drilled by myself. The front panel is made out of thick card, and the filling is made from foam which has been cut to shape. The buttons are made from stack of different sized cardboard rings which have been glued together so that they can move enough to press the buttons on the PCB but are retained by the front panel. A sheet of tracing paper covers the front and enables the LEDs to produce evenly-coloured spots when lit.

Electronics

The game uses a PICAXE-18M2 microcontroller, which is a PIC microcontroller pre-programmed with a BASIC interpreter specifically for the educational market. As a result, it's slow, but it's fine for this application. The 3.5mm jack is used to program the PICAXE microcontroller using a serial cable.

The other DIP ICs on the PCB are serial-to-parallel shift registers which are responsible for driving the LEDs. The only multiplexed part of the design is the matrix keypad. Note that with more programming skill (and probably a faster microcontroller than the PICAXE), the LEDs could have been multiplexed as well, eliminating the need for the external shift registers, but the PICAXE is missing more advanced microcontroller features like timer interrupts (except on larger devices), which would have made multiplexing the LEDs more complex.

A simple 5V linear regulator is used to supply power to the microcontroller from the user's choice of a 9V battery or external DC power supply.

The PCB was originally designed to use 4-pin buttons throughout, but the buttons needed to be substituted with 2-pin buttons so some jumper wires had to be added.

VHDL Teletext: Overview of the project and the FPGA Teletext hardware

Project objective

The aim of this project was to build a fully-featured Teletext decoder using an FPGA. The open-source firmware was written in VHDL. The completed device is the world's first standalone Teletext decoder with an HDMI output, but initially,I implemented a VGA output to learn the basics of generating video from an FPGA.

A brief introduction to Teletext

Teletext was introduced in Europe in 1970s as a system to display text and simple graphics on television sets. A signal contained within the Vertical Blanking Interval (VBI) (of the composite video signal) is decoded by (typically) a custom ASIC in the TV set, which displays the page requested by the user when it is received. World System Teletext (WST) became very popular in Europe and remains in use today (2021) in countries including Germany, Italy, and Ireland. Teletext was also launched in the United States, where it was much less successful, and didn't last very long.

Teletext most commonly carried information for human use such as news, but in the past it also carried programs for computers to use - called Telesoftware.

In the 1990s, Level 2.5 teletext was introduced. It allows Teletext artists to use more colours and more complex graphics. Level 2.5 is not widely supported by television sets, but VHDL Teletext will include some Level 2.5 decoding ability.

Teletext survives despite the switchover from analogue to digital television; the data originally carried in the Vertical Blanking Interval of the analogue picture is now carried as part of the DVB-S signal, and is encoded into the composite video output of most satellite receivers when tuned to an appropriate channel.

Outside of broadcast, Teletext is used as an art form. The Teletext signals can be generated by a Raspberry Pi using vbit2. TEEFAX, started by Peter Kwan in 2016, is one such service that can be run from a Raspberry Pi.

Development process

I've documented key parts of the project development process in detail in my blog:

1. Driving a VGA monitor from an FPGA - I gained an understanding of the basics of FPGA video generation by displaying simple test patterns on a VGA monitor.
2. Page display including Text and Graphics - A basic implementation of the Teletext display generator, incorporating most Level 1 features and using RAM pre-loaded with a fixed page for testing purposes.
3. Data recovery, processing and page extraction - Created the logic for recovering the data from the composite video signal, identifying packets belonging to the requested page, and writing them to dual-port RAM.
4. A sidestep post - programming the FPGA using a MAX 10 FPGA - The FPGA Teletext board (details of the board are below in this blog entry) can be programmed using a Raspberry Pi, offering an alternative to those who do not have or wish to procure a USB Blaster. The Raspberry Pi is a popular generator of Teletext signals, so it is incredibly useful to be able to reprogram the FPGA using it.
5. Generating a high resolution HDMI/DVI output from an FPGA using Double Data Rate I/O - Added the logic to produce HDMI signals at resolutions up to 1280x720.

VHDL-Teletext firmware features

• Open-source firmware GitHub
• Level 1.0 teletext decoder with single-page memory
• Selected Level 2.5 and Level 3.5 features implemented
• Resolution selection via DIP switches: 720x576 or 800x600 at 50Hz or 60Hz (1280x720 available via firmware branch, and 640x480 also possible with minor code modifications)
• Alpha Black enable switch for selecting between adherence to the original specification or compatibility with certain modern teletext services
• Power-on page number selection via DIP switches
• Mix function enables/disables the display of background colours (note that this board does not display the video portion of the composite video signal over HDMI)
• Subpage selection
• Reveal button displays and hides "concealed" page content
• Page selection via number keys, up/down buttons, and Fastext keys
• Level 2.5/3.5 store function for applying enhancements to Level 1.0 pages
• Parameterised design enables design tweaks without any programming knowledge

The hardware: the FPGA Teletext PCB

An FPGA development board designed for the application of decoding WST (World System Teletext) and displaying it on a HDMI monitor/TV. The board is programmed with my open-source VHDL-Teletext firmware and all that's needed to complete the setup is a micro USB power supply, HDMI or DVI monitor, and a source of teletext data with composite video out such as a Raspberry Pi running VBIT2 or a satellite receiver. 50/60Hz output and choice of 576p and 800x600 resolutions for compatibility with international TVs.

Development board hardware features

• 10M08SCE144C8 FPGA
• HDMI output with arbitrary resolution support* with proper current-mode logic level shifter IC
• Composite video input with high-speed comparator for WST sampling
• Micro USB power supply connection - typical current when running teletext decoder firmware is 100mA
• 3.3V 2A switching regulator (plenty of power for external electronics) and 2.5V LDO regulator
• 3-channel programmable oscillator
• 16-way DIP switch
• 20 buttons (including detachable keypad)
• Three I/O headers with 23 I/O pins
• Footprint for optional 512K SRAM for development purposes (footprint can alternatively be used as extra I/O)
• Footprint for optional video processor IC (SAA7113) (this could be used to implement full composite video to HDMI conversion)

* Resolution support tested up to 1280x720. The master branch of the firmware includes support for 720x576 and 800x600 resolutions, and the 720p mode uses the feature/720p branch.

The board is suitable for all manner of FPGA projects. The Altera MAX 10 FPGA has 8k logic elements which is enough for complex hobby FPGA projects. In addition to HDMI connectivity and the built-in keypad and buttons, 23 I/O are connected to headers to allow connection to other devices, providing the potential for diverse applications such as a Telesoftware decoder or a replica of an old microcomputer.

Why did you make it?

I made it because I wanted to create a Teletext decoder which does not depend on obsolete components and has a high-quality, modern, video output connection.

The unique combination of hardware features needed made existing FPGA development boards unsuitable. Limited stocks of old obsolete decoder chips are still available but these only have low-quality composite video outputs and usually only work with PAL TVs.

What makes it special?

This is the world's only standalone teletext decoder with HDMI output.

Hardware for sale

I have assembled a small number of boards by hand and they are up for sale below. If there is serious demand for this PCB, then I will consider getting a proper production run done, and I'll offer a self-assembly kit too. Please comment below on my blog if these are of interest.

Click here to buy the VHDL Teletext PCB on Tindie (fully assembled) - ships from the UK (though all pricing is in USD on Tindie) - please remember that this is currently a very low volume product so I cannot achieve the low pricing of high-volume consumer gear.

Also available on eBay for those who would encounter high fees from their bank/card provider for paying in USD on Tindie or who wish to use the eBay Global Shipping Programme - eBay link.