## If you need second (or third) Fast Gigabit Ethernet interface on your embedded Linux computer or desktop our Open Source Hardware OSHW USB-Gigabit adapter is what you need!

Many of our customers ask if we can design board with two or three Gigabit Ethernet interfaces. The Allwinner chips we use for OLinuXino are general purpose not communication chips so they usually have single Ethernet. The Sitara SOC we use AM335X advertise to have more than one Ethernet interface but it’s marketing as these are virtual interface i.e. share transfer speed.

USB-Gigabit allow you to add 10/100/1000Mbit interface to any of your computers which has USB host. It supports USB 1.1, USB 2.0 and USB 3.0 interfaces and speed depend on your USB port speed.

Our tests with A20 OLinuXino boards with USB 2.0 host interface show 319Mbit of Upload and 295Mbit of Download speed i.e. x3 times more than our other USB-Ethernet-AX88772B interface.

## New compact AC-DC converters for PCB assembly in stock: 5W and 3.5W for 3.3V and 5V

PWR-90-240V-5V1A and PWR-90-240V-3.3V1.5A are compact 51x23x18 mm AC-DC converters for PCB assembly. The input voltage is from 90 to 240VAC so make them suitable for both 110VAC and 220VAC applications.

Operating temperature is -20+60C. Output ripple voltage is 50mV.

PWR-90-240V-5V0.7A and PWR-90-240V-3.3V0.8A are in even smaller form 30x20x18 mm.

## Problem:

Input string which is mathematical statement written in normal Infix Notation and convert it to Postfix Notation.

Infix notation is the normal way we write mathematical statements like:

`(10 + 20) / (30 - 40)`

Postfix notation (also known as Reverse Polish notation) is where every operator follows all of its operands and is parenthesis-free, the above statement written in Postfix notation is:

`10 20 + 30 40 - /`

## The rules:

You can code the solution in any programming language during the weekend and have to submit it to info@olimex.com latest on Sunday July 7th.

On Monday we will upload the solutions on GitHub and review https://github.com/OLIMEX/WPC .

You can play with your real name or with nick if you want to be anonymous, we will not disclosure your personal info if you do not want to.

Good Luck and Have fun!

## Weekend Programming Challenge Issue-13, Solutions

We got only 3 solutions for this challenge! Java, C# and C++

First was Michael Zucchi his solution output the picture above.

Nigel Mollett was second with C# solution. Here is output from his code:

Miller Wang submitted C++ solution and although he do not sort the font in grey scale order also converts the pictures:

Solutions are as usual uploaded to GitHub https://github.com/OLIMEX/WPC/tree/master/ISSUE-13

## Problem: Convert picture to ASCII art

Make code which converts picture to ASCII art.

Hints: This is very easy challenge although seems hard at first sight. Just convert the picture from color to gray scale, then select font which you will use to print ASCII art and analyze it which letters you could use for gray scale print – every letter have some coefficient of filling from 0 for the space to 255 for solid bar, use letters which are spread well in the font size space. Then slice your image at rectangles with the font size, calculate the median grey scale for each rectangle and print the corresponding ASCII character with same grey scale value.

As test image you can use everything – from Olimex logo to Lena above.

## The rules:

You can code the solution in any programming language during the weekend and have to submit it to info@olimex.com latest on Sunday June 2nd.

On Monday we will upload the solutions on GitHub and review https://github.com/OLIMEX/WPC .

You can play with your real name or with nick if you want to be anonymous, we will not disclosure your personal info if you do not want to.

Good Luck and Have fun!

## Low Cost LCD-TO-VGA adapter

A13 processor have no HDMI and VGA output as his big brother A10, so we had to work out something using the LCD interface it have.

We browsed IC video DACs and there is plenty of them, but they are expensive and didn’t fit well OLinuXino low cost concept, so we decided to give a try and make simple R ladder video DAC.

A13 LCD interface is 18 bit this means we will need 3 channels x 6 bit Video DAC.

All VGA monitors have 75 ohm terminator on their input lines and the video signal is 0.75V for white level and 0V for black. So knowing this we could make resistor ladder DAC with R, 2R, 4R, 8R, 16R, 32R connected in parallel with RGB 0-5 bits. The values are easy to calculate when we know the LCD buffer output voltage 3.3V and the voltage we want to have when all bits are “1” i.e. 0.75V. The resistors using the 1% precission values picked were 549 ohm, 1050 ohm, 2180 ohm, 4370 ohm, 8660 ohm, 17800 ohm.

The adapter was routed and pcb prototypes were run. The assembled adapter was attached to LPC1788 board with 4.3″LCD with tweaking the output to match VGA lock frequency and the result was perfect.

The picture which appears on LCD was color stripes with small ball which you can move by tilting the board (using on-board accelerometer), as you can see from the picture the colors are perfect and image is standing still with no glitches and jitters.

So now we have low cost VGA solution for our A13-OLinuXino and can move forward with the PCB schematic finish and routing. Note that the VGA signals go through buffers which are gated i.e. we can enable and disable the VGA output and A13-OLinuXino will be able to work with both LCDs and VGA.

EDIT: schematic is included here below: