### ATmega169 base 8bit Arithmetic and Logic Unit

ALU (Arithmetic and Logic Unit) is a digital system that performs integer arithmetic and logical operations. In this post we introduce ATmega169 base ALU simulation using Proteus. This is 8bit ALU, and functionally it is similar to other entry level ALUs such as Motorola MC14581, 74LS181, etc. This unit can perform 80 arithmetic and logic operations and all these operations are listed in below of this post.

 schematic of ATmega169 base 8bit ALU simulation

Firmware of this ALU is developed using AVR-GCC. While at the development we try to isolate firmware with platform as maximum as possible, because of that, this firmware can be modified to run on top of PIC, 8051 or MSP430 MCUs with minor set of changes.

• A: Input A
• B: Input B
• Z: Output
• EO: Overflow
• Ei: A = B
• FF = 0xFF ( = 255)

 Instruction Expression Comments 00 Z = A EO = 0 01 Z = B EO = 0 02 Z = ¬A EO = 0 03 Z = ¬B EO = 0 04 Z = A ∧ B EO = 0 05 Z = ¬ (A ∧ B) EO = 0 06 Z = (¬A) ∧ B EO = 0 07 Z = A ∨ B EO = 0 08 Z = ¬ (A ∨ B) EO = 0 09 Z = (¬A) ∨ B EO = 0 0A Z = A ⊕ B EO = 0 0B Z = ¬(A ⊕ B) EO = 0 0C Z = (¬A) ⊕ B EO = 0 0D Z = 0 EO = 0 0E Z = A + B ((A + B) > FF) → (EO = 1) 0F Z = A - B (B > A) → (EO = 1) 10 Z = A × B ((A × B) > FF) → (EO = 1) 11 Z = A ÷ B (B > A) → (EO = 1) 12 Z = max{A,B} EO = 0 13 Z = min{A,B} EO = 0 14 Z ≈ √A EO = 0 15 Z = !A (A > 5) → (EO = 1) 16 Z = AB (AB > FF) → (EO = 1) 17 Z = A - 1 (A = 0) → (EO = 1) 18 Z = A + 1 (A = FF) → (EO = 1) 19 Z = (A ∧ B) - 1 ((A ∧ B) = 0) → (EO = 1) 1A Z = (¬ (A ∧ B)) - 1 (¬ (A ∧ B) = 0) → (EO = 1) 1B Z = (A ∧ B) + 1 ((A ∧ B) = FF) → (EO = 1) 1C Z = (¬ (A ∧ B)) + 1 (¬ (A ∧ B) = FF) → (EO = 1) 1D Z = ((¬A) ∧ B) + 1 (((¬A) ∧ B) = FF) → (EO = 1) 1E Z = (A ∧ (¬B)) + 1 ((A ∧ (¬B)) = FF) → (EO = 1) 1F Z = ((¬A) ∧ B) - 1 (((¬A) ∧ B) = 0) → (EO = 1) 20 Z = (A ∧ (¬B)) - 1 ((A ∧ (¬B)) = 0) → (EO = 1) 21 Z = (A ∨ B) - 1 ((A ∨ B) = 0) → (EO = 1) 22 Z = (¬ (A ∨ B)) - 1 (¬ (A ∨ B) = 0) → (EO = 1) 23 Z = (A ∨ B) + 1 ((A ∨ B) = FF) → (EO = 1) 24 Z = (¬ (A ∨ B)) + 1 (¬ (A ∨ B) = FF) → (EO = 1) 25 Z = ((¬A) ∨ B) + 1 (((¬A) ∨ B) = FF) → (EO = 1) 26 Z = (A ∨ (¬B)) + 1 ((A ∨ (¬B)) = FF) → (EO = 1) 27 Z = ((¬A) ∨ B) - 1 (((¬A) ∨ B) = 0) → (EO = 1) 28 Z = (A ∨ (¬B)) - 1 ((A ∨ (¬B)) = 0) → (EO = 1) 29 Z = B - 1 (B = 0) → (EO = 1) 2A Z = B + 1 (B = FF) → (EO = 1) 2B Z = (A ⊕ B) - 1 ((A ⊕ B) = 0) → (EO = 1) 2C Z = (¬ (A ⊕ B)) - 1 (¬ (A ⊕ B) = 0) → (EO = 1) 2D Z = (A ⊕ B) + 1 ((A ⊕ B) = FF) → (EO = 1) 2E Z = (¬ (A ⊕ B)) + 1 (¬ (A ⊕ B) = FF) → (EO = 1) 2F Z = ((¬A) ⊕ B) + 1 (((¬A) ⊕ B) = FF) → (EO = 1) 30 Z = (A ⊕ (¬B)) + 1 ((A ⊕ (¬B)) = FF) → (EO = 1) 31 Z = ((¬A) ⊕ B) - 1 (((¬A) ⊕ B) = 0) → (EO = 1) 32 Z = (A ⊕ (¬B)) - 1 ((A ⊕ (¬B)) = 0) → (EO = 1) 33 Z = (A ∨ B) - A ((A ∨ B) = 0) → (EO = 1) (A > (A ∨ B)) → (EO = 1) 34 Z = (¬ (A ∨ B)) - A (¬ (A ∨ B) = 0) → (EO = 1) (A > ¬ (A ∨ B)) → (EO = 1) 35 Z = (A ∨ B) + A ((A ∨ B) = FF) → (EO = 1) 36 Z = (¬ (A ∨ B)) + A (¬ (A ∨ B) = FF) → (EO = 1) 37 Z = ((¬A) ∨ B) + A (((¬A) ∨ B) = FF) → (EO = 1) 38 Z = (A ∨ (¬B)) + A ((A ∨ (¬B)) = FF) → (EO = 1) 39 Z = ((¬A) ∨ B) - A (((¬A) ∨ B) = 0) → (EO = 1) (A > ((¬A) ∨ B)) → (EO = 1) 3A Z = (A ∨ (¬B)) - A ((A ∨ (¬B)) = 0) → (EO = 1) (A > (A ∨ (¬B))) → (EO = 1) 3B Z = (A ∧ B) - A ((A ∧ B) = 0) → (EO = 1) (A > (A ∧ B)) → (EO = 1) 3C Z = (¬ (A ∧ B)) - A (¬ (A ∧ B) = 0) → (EO = 1) (A > ¬ (A ∧ B)) → (EO = 1) 3D Z = (A ∧ B) + A ((A ∧ B) = FF) → (EO = 1) 3E Z = (¬ (A ∧ B)) + A (¬ (A ∧ B) = FF) → (EO = 1) 3F Z = ((¬A) ∧ B) + A (((¬A) ∧ B) = FF) → (EO = 1) 40 Z = (A ∧ (¬B)) + A ((A ∧ (¬B)) = FF) → (EO = 1) 41 Z = ((¬A) ∧ B) - A (((¬A) ∧ B) = 0) → (EO = 1) (A > ((¬A) ∧ B)) → (EO = 1) 42 Z = (A ∧ (¬B)) - A ((A ∧ (¬B)) = 0) → (EO = 1) (A > (A ∧ (¬B))) → (EO = 1) 43 Z = (A ⊕ B) - A ((A ⊕ B) = 0) → (EO = 1) (A > (A ⊕ B)) → (EO = 1) 44 Z = (¬ (A ⊕ B)) - A (¬ (A ⊕ B) = 0) → (EO = 1) (A > ¬ (A ⊕ B)) → (EO = 1) 45 Z = (A ⊕ B) + A ((A ⊕ B) = FF) → (EO = 1) 46 Z = (¬ (A ⊕ B)) + A (¬ (A ⊕ B) = FF) → (EO = 1) 47 Z = ((¬A) ⊕ B) + A (((¬A) ⊕ B) = FF) → (EO = 1) 48 Z = (A ⊕ (¬B)) + A ((A ⊕ (¬B)) = FF) → (EO = 1) 49 Z = ((¬A) ⊕ B) - A (((¬A) ⊕ B) = 0) → (EO = 1) (A > ((¬A) ⊕ B)) → (EO = 1) 4A Z = (A ⊕ (¬B)) - A ((A ⊕ (¬B)) = 0) → (EO = 1) (A > (A ⊕ (¬B))) → (EO = 1) 4B Z = flip{A} EO = 0 4C Z = flip{B} EO = 0 4D Z = random{0..FF} EO = 0 ; see note in below 4E Z = Z | random0 = A EO = EO ; see note in below 4F Z = Z | random0 = B EO = EO ; see note in below

Note 1:

In this system random numbers are generated using linear congruential generator algorithm, therefore:

randomn + 1 = (a randomn + C) mod m

If not initialized random0 = 0.

The Proteus simulation and ATmega169 firmware is available to download at google drive. This is an open source software project and all the content are licensed under the terms of MIT license.

### Enable WebRTC on QtWebEngine for Raspberry Pi 3

WebRTC is a web technology to enable peer to peer communication in real-time. It mainly uses to create video conferencing and chat applications using web browsers. In this post, we describe how to enable this technology in QtWebEngine on Raspberry Pi 3 platform.

QtWebEngine is an embedded browser component which comes with the Qt framework. This component is based on Google Chromium browser and it supports most of the Chromium features including WebRTC. In PC, WebRTC applications run smoothly on QtWebEngine component. But in Raspberry Pi platform situation is different and none of the WebRTC application is work with the QtWebEngine. The only thing which we can see is a black box in an HTML5 video tag area. At the time of writing this problem exists in Qt version 5.6, 5.7 and 5.8.

### BMP180 based USB atmospheric pressure monitor

We initially developed this USB atmospheric pressure monitor to study some operating characteristics of Bosch BMP180 sensor. BMP180 is a low-cost sensor for measuring barometric pressure and temperature. According to the datasheet this sensor can use to measure pressure ranging between 300hPa to 1100hPa. This sensor is introduced a couple of years back but still, it is popular due to lower cost and simplicity of its interface.

We did this unit to test the BMP180 sensor more accurately and to study its behaviors. This unit is based on PIC18F2550 microcontroller and the main reason to select this MCU is because of its built-in USB 2.0 interface.

To display sensor calibration data and it’s readings we did small windows application. This application display and plot temperature and pressure readings captured from the BMP180 sensor.

This unit is programmed to work as a USB HID device and no special device driver is required to use this device. We test this unit in Windows 10 environment.

### Programmable light controller

The main objective of this project is to design a maintenance free and low-cost light which automatically turns on and off at the predetermined time of the day.

To meet the above requirement I designed this controller using ATmega8 MCU and DS1307 RTC. The driver stage of this light controller is intended to work with commonly available 7W LED modules.

The core component of this programmable light is ATmega8 low power CMOS microcontroller. The main reason to select this microcontroller is it’s lower cost and higher availability. Except for the above two reasons this microcontroller also bundled with a rich set of peripherals which including 23 GPIOs, 3 independent timers, Two-wire serial interface, EEPROM, etc.

Apart from ATmega8 microcontroller, this system uses DS1307 real time clock to maintain system time. Like ATmega8, DS1307 is also a very popular RTC in the market.

This controller is designed to work with a 24V DC power supply. The main reason to select 24V is that most of the…