Ralph shared his auto-reset feature of his Arduino board. He writes:
Various versions of the Arduino will reset the board by toggling the serial DTR line, a feature called auto-reset. Since it relies on the DTR line, it won’t work with TTL serial adapters that don’t break out the DTR line. After writing my half-duplex serial UART, I thought of using the TTL serial break signal which holds the line at 0V for several ms. Normal serial communications would also send 0V, but at 57.6kbps, it would never last more than 160us before returning to the idle high voltage state. So what I needed was a circuit would not reset when the line is low for 160us, but would reset when the line is low for 100ms or more.
Zero-wire serial auto-reset for Arduino - [Link]
asidorenk @ obddiag.net pointed us to this great little USB to Serial board:
This USB to serial (TTL) converter project is easy to build, it is simple and inexpensive. It is based on the PL2303SA USB to USART bridge from Prolific. The PL2303SA chip is not required an external crystal as the internal clock oscillator is continuously tuning up to USB bus frequency. Having chip in SO-8 packaging does not require special soldering skills to assemble the project. Please note: the TX and RX signal levels are 3.3 Volts.
USB to Serial Breakout Board for Prolific PL2303SA - [Link]
Chris from pyroelectro says that designing circuits with pure TTL chips is fun, something that i totally agree with. This time, he used an analog tilt sensor to read the tilt of the board, and an 8 by 8 led matrix for display. He used only analog chips to implement this project. Good work!
Pure analog tilt sensor - [Link]
This morning I decided its about time I learn how to use the UART hardware in most PIC microcontrollers. I started off with a USB-RS-232 converter that I got for US$3 from DealExtreme. There are a few reasons why I used a converter, firstly being because my main PC no longer has an RS-232 port since its old tech, but also because I thought it’d be alot neater for my projects to have a USB connection and it means I can interface with TTL signal levels (0-5v) instead of the RS-232 standards -12v – +12v which would have added complications, but we’ll get back to that just now…
Learning Serial Communication - [Link]
The last project I built, the Masochist’s Video Card reminded me of how fun pure TTL digital design can be and since the 7400 contest seems to be allowing multiple entries, I figured why not build something else?
The accelerometer is an interesting sensor that is now extremely tiny thanks to MEMS technology. Specifically, the accelerometer senses gravity, and since earth has a constant 1 g-force always pulling toward the center, we can use that reference to find the tilt of any object. With some digital design and LEDs added to the mix we can even build a tilt sensor as I will show you in this article.
TTL Tilt Sensor - [Link]
A friend of mine suggested that I build something for a 74xx TTL discrete logic contest at dangerous prototypes, so I figured why not? If you like this design, make sure to leave a comment on their website for my competition entry.
The Masochist’s video card is a pure TTL discrete logic design that generates the necessary video signals for VGA. The project name came about after the hours I spent wire-wrapping the project together yielded painfully raw fingertips. So be fore-warned if you duplicate this project, don’t abuse the wire-wrap tool!
Masochist’s Video Card - [Link]
Driving an adafruit VC0706 TTL Serial JPEG Camera with a Netduino @ Fabien’s Bit Bucket. [via]
Earlier this month, AdaFruit released a nice little TTL camera, perfect for security and remote monitoring applications. The camera supports three resolutions (640×480, 320×240 and 160×120), has a built-in motion detection circuit and can output an NTSC signal, all in a fairly compact form factor. The communication with the camera is done over a TTL UART @ up to 115200 bauds…
As I’m working on a security-related project involving the Netduino, it was the perfect opportunity to put this camera to the test, starting with writing a C# driver. While interfacing with the camera over the TTL UART of the Netduino is straight forward, the datasheet describing the protocol and commands required to control the camera functions is painfully sketchy and sometime inaccurate. In some instances, some camera functions such as OSD (text overlay) are not supported in the firmware even though the datasheet documents them or only behave properly if called in a particular sequence, which of course, is not documented…
Driving an adafruit VC0706 TTL Serial JPEG Camera with a Netduino - [Link]
adafruit.com writes: [via]
This tutorial is for our new TTL serial camera module with NTSC video output. These modules are a nice addition to a microcontroller project when you want to take a photo or control a video stream. The modules have a few features built in, such as the ability to change the brightness/saturation/hue of images, auto-contrast and auto-brightness adjustment, and motion detection.
TTL Serial Camera Tutorial - [Link]
This page features a circuit that has twenty open collector outputs that turn on one at a time in a continuous sequential manner. The circuit make use of the 74LSxx family of TTL integrated logic devices. The circuits are designed to drive light emitting diodes or low current, low voltage incandescent lights but can also drive other loads of up to 80 milliamps.
Traffic Light Control Circuit – [Link]
If you like gambling, you should have this toy in your collection. Electronic dice (die) is very easy to build – it uses several component and quite few code lines. Here you can find several Electronic die projects designed for different PIC microcontrollers by Pete Griffiths. These can be built on prototyping breadboard or as single application. Projects are ready for PIC16F84, PIC12F675, PIC16F690 and even on hard TTL logic. [via]
Electronic dice projects on PIC microcontrollers - [Link]