A great tool for microcontroller hacking activities you might want to take on in the future is the Baudrate Converter, a device that automatically detects the baud rate of an MCU-based device you wish to hack. Using this method makes things a lot easier, so you don’t have to detect the actual baud rate using the PC or an oscilloscope – it saves a lot of time and energy and it’s also pretty simple to make.
The usual serial transmission has the Tx line on ‘high’ when idle and a single byte starts with a ‘low’ value (the startbit) and ends with a ‘high’ value (the stopbit). The idea is that, based on a few characters, the device measures the times the signal is ‘low’ and sorts them lowest to highest, detecting the real bit-time.
The baud rate converter uses the ATtiny2313 microcontroller from Atmel and the FT232 USB UART chip from FTDI. The latter supplies the power for the ATtiny. The converter has no capacitors for the crystal and runs at 20MHz using a 3.3V voltage, but it seems to be working nonetheless. The software that makes everything work is written in C and uses the 16-bit timer of the ATtiny extensively. After you connect the unknown serial port and send a few characters via a terminal-emulator, the device will detect the baud rate and the transmission of the bytes will be done accordingly, using the appropriate baud rate. If errors are detected, the converter will repeat the autobauding process.
The device has a detection range from 110 to 115200 and can help a great deal if you encounter baud rate conversion difficulties. The source code is available for released under GPLv3 license and is available for download in the link below (a .hex file is also available).
An older project (but quite interesting nevertheless), this is an RDS decoder that is able to display various information on a 2 lines with 16 characters alphanumeric LCD. The decoder is connected to an old radio receiver and was originally designed to use the Atmel AT90S2313 as its brain, coupled with TDA7330B RDS demodulator as the decoding-chip. The newer version had the AT90S2313 replaced with the ATtiny2313 microcontroller.
The device can display service name, RDS clock, TA (Traffic Announcement) flag status and scrolling 64 characters long radio text. The decoder requires a Stereo multiplex signal as input, which can be found at the input pin of a Stereo decoder integrated circuit in most radio receivers. The code is written in assembler, which provides for the fastest implementation. There is also a C version of the code, but apparently it’s too big for the 2KB flash memory of the ATtiny2313. However, an improved, smaller C version might be available sometime in the future.
Check links for .zip with PCB layout, schematics and source code (for both the ATtiny and the AT90).
RDS Decoder using Atmel Microcontroller: [Link] – [via]
This is probably the most compact led matrix display ever, you need the ATtiny2313 and 8×8 Led matrix and off course two AA batteries for power. The micro controller is on the back of the display, soldered directly to the pins, since the voltage of two AA cells is around 3V you don’t need the current limiting resistors either. Just remember to use the low voltage type of micro controller like the ATTINY2313V-10PU the ATTINY2313-20PU won’t work, and in case of powering from 5V put some 100Ohm resistors in series with the leds.
This project can be easily adapted to other controller or display, but the ATtiny2313 and the LEDMS88R’s pin configuration fit together perfectly, no need for wire bridges to match the right pins.
With the 64 pixels you can’t display complex messages but there is enough resolution to achieve some eye catching animations, and the battery will last for two weeks. The size can be further reduced if you use small, coin shaped lithium cells instead of the bulky AA batteries.
The controller is actually just an ATTiny2313, running of it’s internal RC oscillator at 8MHz, soldered onto an universal board with a few resistors and wires. There are no control items – no buttons, no nothing. It just does what it does – makes the effect of LEDs randomly fading in and out using 9 channels of PWM. Unfortunately, the processor has only a few hardware PWM channels, so some of the channels had to be done by software.
With this small board you can program most of the AVR ATTiny microcontrollers or you can build your projects to use it in a stand alone application. It can be powered with a 9V battery because it has 5V voltage regulator on it. The voltage regulator can give 1000mA current. The power to the board can also be supplied with a wall wart. Low power external devices like a LCD module can be powered via the board itself.