by Publitek European Editors
This article looks at the latest touchscreen sensor technologies and the wide range of interfaces that the different technologies use. It also evaluates the different approaches for interfacing such sensors for human interfaces from three, four and five wire to USB, covering sensors and interfaces from Atmel, 3M, IR Touch Systems, and NKK Switches. Resistive 4- and 5-wire touch sensors are the most popular and most common touchscreen technologies with about 75% market share, mainly due to their low costs and simple interface electronics. The high volume of these screens requires a low-cost reliable interface, often with a low-power element. This can be provided through a range of analog features combined with low-power modes for portable, battery-powered applications.
Evaluating Different Approaches for Interfacing Touchscreens – [Link]
Brian Schmalz writes:
The UBW board is a small board that contains a Microchip PIC USB-capable microcontroller, headers to bring out all of the PICs signal lines (to a breadboard for example), only costs about $15-$20 to build and is powered from the USB connection.
UBW – USB Bit Whacker- inexpensive, simple input/output USB device – [Link]
This app note describes the common IC interface protocols like I2C, SPI, and GPIO. Also some problems covered with these interfaces that turn happy faces to sad. [via]
How can an interface change a happy face to a sad face? Engineers have happy faces when an interface works properly. Sad faces indicate failure somewhere. Because interfaces between microprocessors and ICs are simple—even easy—they are often ignored until interface failure causes sad faces all around. In this article, we discuss a common SPI error that can be almost impossible to find in a large system. Links to interface tutorial information are provided for complete information. Noise as a system issue and ICs to minimize its effects are also described.
Common IC interface problems – [Link]
The LTM2883 is a 6-channel SPI/Digital or I2C digital μModule isolator with triple rail regulated power for 3.3V and 5V systems. In industrial systems applications, ground potentials can vary widely, often exceeding the tolerable range, which can interrupt communications or even destroy components. The LTM2883 breaks ground loops by electrically separating communications signals, isolating the logic level interface on each side of an internal inductive isolation barrier that withstands a very large common-mode voltage range up to 2,500VRMS. The LTM2883’s low EMI isolated DC-DC converter powers the communications interface and provides adjustable 5V, +12.5V, and -12.5V supply outputs, ideal for powering data converters in data acquisition systems. With 2,500VRMS of galvanic isolation, onboard secondary power and a communications interface operating at up to 20Mbps, the LTM2883 requires no external components and provides a simple μModule solution for isolated data communications.
LTM2883 – SPI/Digital or I2C μModule Isolator with Adjustable Regulated Power – [Link]
This table provides top-level characteristics for serial interface standards by which two or more digital devices can be connected for communication. Design engineers can use the table to compare interface options for their application based on the design constraints like number of signal lines, network size, speed, distance, noise immunity, fault tolerance and reliability.
Serial Data Communication Protocols Comparizon – [Link]
Haris Andrianakis writes:
One of my latest projects i just finished is a hardware thermal printer driver. This project designed/developed for “Delmac Instruments” as a part of my internship. Thermal printers are used in cash and weighting machines for receipt printing.
What the specific hardware does is to receive ASCII characters, escape sequences in UART and convert them in a printable form to send to printer mechanism for printing. Escape sequences are used to send commands to the printer to change character size, line spacing etc.
Thermal Printers don’t use ink as usual printers but they have a head of tiny resistors in a row (about 384) which behave on the paper as dots. Also they use a suitable paper which is thermal sensitive.
By supplying voltage to a single resistor, you heat the resistor and you make the paper burn at the specific point drawing a tiny single dot on the paper. If you supply voltage to a single resistor and you move the paper at the same time by stepping the head motor you will have a tiny width vertical row. This is the basic. (Resistors are refered as elements).
Thermal Printer Driver – [Link]
Boris Ribov, Georgi Bakalski writes:
If you have a website, blog or any other web service then the etherfeed is for you. The etherfeed is a small standalone network device, it connects to the Internet and displays statistical data about your website like number of unique visitors, number of pageviews, PayPal sales (SUM of sales via the PayPal IPN), Facebook likes for your brand / group and weather data like temperature, humidity for your location.
How it works?
The system consist of two parts. The first part is a set of php scripts responsible for collecting data from Google Analytics, PayPal, Facebook and Google weather data. These scripts shall be installed on the target website.
The second part is the etherfeed device which connects to the internet via a router, and access one of the above mentioned php scripts, collects the data and displays it on the etherfeed 16×1 Blue backlight LCD Display.
Etherfeed – tickling your ego or statistics? – [Link]
Kerry uses a DIY serial display to show debugging data sent from an Arduino’s UART. Sometimes the data comes too fast to read, so he added a 4K buffer and controls to scroll thorough the history. [via]
…if your application generates a lot of messages, it would still be hard to spot the relevant information as you can only see the last couple of lines of the data.
So my solution is to add a none-volatile off-screen buffer to the serial display so that multiple rows of data can be captured during run time and retained for later debugging.
Serial port monitor with 2×20 LCD and 4K text buffer – [Link]
Charalampos Andrianakis writes:
The idea of explaining here how a rotary encoder works began from the need to use a rotary encoder myself for adjusting a PWM which drives a DC motor. So i started looking for how a rotary works. When i understood how it works i thought that it could be a good idea to show you and explain what i learned.
Anyone who has worked on circuits before has used an analog potentiometer. If you are new in electronics here is a quick explanation of what a potentiometer is. In a few words a potentiometer is a varying resistor which value changes by turning the knob. By the Ohm Law V=I*R implies that it can be used for voltage or current adjustments. An example of potentiometers use is in front panels for varying values e.g in a work bench power supply to adjust the voltage or the current.
Well the potentiometers have some disadvantage.
- Produce noise at knob turn over the uses or if dust has passed in.
- They are not that accurate.
- To use them in a digital circuit you have to use an Analog To Digital converter.
On the other hand Rotary Encoder.
- There is no noise production (if you use the appropriate capacitors).
- They are accurate (they have steps).
- There is no need of a digital to analog converter.
3-pin Rotary Encoder How to – [Link]
Displaying content on a normal alphanumeric display is very limited ,we have to be limited with the font size and we can’t draw any graphics also. but convention Graphics lcd are really very expensive so here is the solution, you can use Nokia 3315 monochrome LCD to display your large font text and graphics . the reason behind using this LCD is ,it is really very cheap and can be powered with 3 volts supply. so it is really good for battery powered application.
Nokia 3315 LCD interfacing with Microcontroller – [Link]