A touch numeric keyboard for Arduino or Teensy

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Giovanni Carrera blogged about his touch numeric keyboard for Arduino or Teensy:

Very often, for our programs, we need a system to set parameters, usually of a numerical type. A 4×4 keyboard requires some space and then we also need a display. Here is the idea of using a touchscreen display to do both. I have then written the GetNum function that allows you to print a prompt message and to type an integer number. To test this function I wrote a simple analog data logger program that required two parameters, the first is the sampling period and the second the number of samples. In this example the number of channels to be scanned is set to three, but the program can be modified to request a third parameter with the number of channels.

See the full post on ArduPicLab blog.

App note: ASIC fixes for noisy analog “Oops”

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App note from Maxim Integrated about simple fixes that can solve most issues when designing with ASICs. Link here (PDF)

Noise is a common problem in mixed-signal ASICs, degrading performance and jeopardizing the completion of products. This application note gives hints and tips for adding external circuits that make many of these ASICs operational for prototyping or shippable as final products. Ways to optimize the ASIC by correcting noise in analog circuits, making adjustments, calibrating gain and offset, and cleaning power sources are discussed. The payoff is quicker time to market and even the prevention of an extra ASIC manufacturing spin.

Adding ADC to Microcontrollers without ADC

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Scott Harden writes:

I recently had the need to carefully measure a voltage with a microcontroller which lacks an analog-to-digital converter (ADC), and I hacked together a quick and dirty method to do just this using a comparator, two transistors, and a few passives. The purpose of this project is to make a crystal oven controller at absolute minimal cost with minimal complexity. Absolute voltage accuracy is not of high concern (i.e., holding temperature to 50.00 C) but precision is the primary goal (i.e., hold it within 0.01 C of an arbitrary target I set somewhere around 50 C).

More details at Scott Harden’s blog.

App note: Interfacing AT84AD001B dual 8-bit 1 Gsps ADC and AVR ATmega128L

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e2v’s application note interfacing their 1 Gsps 8-bit ADC to AVR. Link here (PDF)

With its smart feature (3-wire serial interface), e2v’s AT84AD001B dual 8-bit 1 Gsps ADC provides you with digital control over various functions offered with the dual ADC: calibration, gain and offset adjustments, DMUX ratio selection, analog and clock input mode, and partial or full standby mode.

This digital control via the 3-wire serial interface can be managed using Atmel’s ATmega128L AVR. The aim of this application note is to provide you with the relevant information for interfacing these two devices.

App note: Peak-to-peak resolution versus effective resolution

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Effective resolution is superior compared to peak-to-peak resolution when comparing ADCs from different companies. An application note from Analog Devices. Link here (PDF)

The low bandwidth, high resolution ADCs have a resolution of 16 bits or 24 bits. However, the effective number of bits of a device is limited by noise. This varies depending on the output word rate and the gain setting used. This parameter is specified by some companies as effective resolution. Analog Devices specifies peak-to-peak resolution, which is the number of flicker-free bits and is calculated differently from effective resolution. This application note distinguishes between peak-to-peak resolution and effective resolution.