Thursday, May 24, 2018

Analog to Digital Converter (ADC) library for AVR microcontrollers

This library provides a quick and easy way to set up an ADC on AVR microcontrollers and retrieve the values in 8-bit or 10-bit format in an interrupt driven fashion.

Nowadays even the cheapest microcontroller has a build-in ADC (Analog to Digital Converter). An ADC converts analog signals into digital signals and can be used in a wide range of applications like recording a signal from a microphone into a digital format, reading light sensors like an LDR (light dependent resistor), measuring current consumption, reading temperature or humidity sensors, etc. All these requires voltage measurements that an ADC can do.



Wednesday, May 23, 2018

Watchdog library | AVR microcontrollers | ATmega328P

Even if you are a dog or a cat person, you should still be using the watchdog.

For those who don't know, a watchdog is a timer inside the microcontroller generated by an RC oscillator - with 128kHz frequency on an AVR device. When it times out, the microcontroller is reset. To prevent it from resetting the MCU, the watchdog timer must be reset by the code inside the while loop. The idea is that if you have a loop and gets stuck, the watchdog timer will not be reset and so the microcontroller will be reset after the timer reaches the timeout period. Say you read a sensor and in a loop the code waits for the sensor response but the sensor is malfunctioning. If not for the watchdog, the MCU will get stuck and your drone will crash.



Watchdog extension library for AVR microcontrollers

On ATmega328 the available timeouts are 16ms, 32ms, 64ms, 0.125s, 0.25s, 0.5s, 1s, 2s, 4s, 8s. Choosing the right timeout depends on the specific application. The while loop must be able to finish executing the code and reset the watchdog timer before the timer runs out. For critical applications where if the CPU being stuck for more than 1 second is unacceptable, you can choose timeouts of a few milliseconds. Those cases can be a drone where reaction time needs to be fast, or a 3D printer reaches the end and the motor needs to be stopped in time. But in most cases the timeout can even be 8s, like when taking room temperature readings.

Other uses for the Watchdog timer

Tuesday, May 8, 2018

Library for reading multiple buttons with 1 ADC pin | AVR microcontrollers

There are many ways of reading switches, and one of them is using ADC pins. The advantages of this method is that it uses very low pin count compared to other methods, and all is needed are switches, resistors and an ADC (analog to digital converter). With a 10bit ADC, at least 20 switches can be used per pin.

To read the buttons the conventional way where every button is connected directly to a GPIO pin, check out this other library https://www.programming-electronics-diy.xyz/2021/01/button-debouncing-library-for-avr.html.

Library Features

  • Supports multiple groups of buttons on different ADC pins
  • Ability to read combination of multiple button press on different ADC pins
  • Can have different number of buttons on each pin
  • Check if a button was pressed for a certain amount of time
  • Timer 2 and ADC is setup by default 

Reading buttons using ADC (configuration #1)

Reading buttons using ADC - Configuration 1
Fig. 1 Reading buttons using ADC (configuration #1)

Tuesday, April 24, 2018

Eagle CAD Tip | How to export PCB layout to an image

If you are planning to make your own PCBs, using toner transfer or UV exposure methods, you will need the layout image and maybe the silkscreen. With a little script file this can be done in a few seconds in Eagle.

Export a PCB layout image in Eagle CAD using script


Tuesday, March 27, 2018

LC75824 LCD driver chip library for EFM8 microcontrollers

LC75824 is an LCD driver chip. It has 4 commons so it has 1/4 duty and supports 1/2 and 1/3 bias voltages. In addition to being able to directly drive up to 204 LCD segments, the LC75824E and LC75824W can also control up to 12 general-purpose output ports. Serial data input supports CCB format communication with the system controller.
The interface between the LCD driver and the microcontroller is done by using only 3 pins (CLK, CE and DATA).
I know this is an old and rare LCD driver but the library code can be used to adapt other LCD drivers. I use this because I have a broken Samsung MM-N7 audio system with a good display using this IC.

LC75824 pinout
LC75824 pinout

Sunday, March 4, 2018

UART library for EFM8BB1 Busy Bee microcontrollers


This UART library is made for EFM8 microcontrollers. It uses circular buffers for transmission and reception of data. This way large amounts of data can be sent or received with only 5 or 10 bytes per buffer, thus saving memory.
Uses 8 data bits, 1 stop bit, no parity. Supported baud rates: 9600, 14400, 19200, 38400, 57600, 115200, 128000, 256000.



On EFM8BB10F8G-A device, the UART pins are on port 0 and pin 4 is TX and pin 5 is used for RX.

EFM8BB1 SOIC16 pinout

Saturday, March 3, 2018

Eagle CAD Quick Tip | How to remove unwanted copper pour

Beautify your PCB with this quick tip. A short video on how to remove unwanted copper pour around some traces in Eagle CAD without increasing the clearance between tracks.