At this time, I will present a kind of "bugfix" for the device from the previous article . Another version of the implementation, see the following .

Having looked at the resulting bike, an idea came to correct how badly it could be. Namely:

• expand remote control capabilities;
• reduce the cost;
• come up with something with the transfer of video that would be at least a little more comfortable to work remotely.

I’ll just say something from the video that didn’t come up, I’m going to have to be content with what we have, but let's not talk about sad things.
')
And so proceed, with clean hands, a cold head and a warm heart. The components have changed dramatically instead of the Raspberry PI, we will use the Orange PI and instead of the Arduino UNO only the very microcircuit (Atmega16u2) that was discussed in the last article.

The number of components has not changed:

1. UVC video capture card:



2. VGA to AV Converter:



Experimented with another converter, here with this:



But the miracle did not happen, the video quality did not improve, but on the contrary.

3. Atmega16u2:



4. Orange PI in my case Orange pi PC model:



A few words about this micro computer. It is based on the Allwinner H3 processor (a good cheap 4-core processor on the AWP architecture), 1 GB of RAM 3 USB, HDMI, and so on, a full description is not difficult to find on the Internet.

Preparatory stage

Install the operating system on Orangepi

Here is a link to the forum, in this forum thread there is a lot of useful information, but of course everything is in English, we are interested in the OrangePI-PC_Ubuntu_Vivid_Mate.img distribution, you can download it from mega.nz or Google Drive. We find the Download from Mega or Google Drive line in the header, click on the desired link, download it.

The procedure for transferring an image to a USB flash drive is the same as for a flash drive; on Windows, you can use win32 disk imager writer on Linux with the dd command.

A small digression. Orange pi and similar microcomputers built on Chinese Allwinner processors are pretty much inferior to hardware not by hardware (hardware), but by software (software), more precisely by capabilities and OS "completeness", so to speak. A trimmed kernel, an un-optimized file system, a huge number of bugs, these are not all problems. This situation arose due to the fact that the processor manufacturer initially focused on tablets (maybe even smart phones) running Android, and from the manufacturer’s point of view, there wasn’t any economic expediency in a full-fledged Linux distribution. The Linux kernel was trimmed to the very tomatoes, from a full life turned into a vegetable, capable only of primitive actions. For a long time there were Linux distributions on the core of the android, probably a kind of cheap marketing ploy, and so it would have continued if not for the enthusiasts.

But back to our sheep. Distribution recorded, the system is running.

Adjust the motion

Go to the console. orangepi root or root orangepi password

Update packages:

 sudo apt-get update && sudo apt-get upgrade –y 

Set Motion

All settings as in the previous article:


The console is not closing yet.

Preparing to compile

For the transfer of control, we will write a program, everything will be described below in more detail, in the meantime, we will make basic preparations.

Install everything you need to compile, our program will be in C:

 sudo apt-get install build-essential -y 

Install the ncurses library, using it we will capture the key values:

 sudo apt-get install ncurses -y 

We make ourselves the owner of the serial port so that we can record:

 sudo chown orangepi /dev/ttyS2 

Open the kernel module loading config in the editor:

 sudo nano /etc/modules 

Uncomment the gpio-sunxi . With this action we activate gpio, more precisely, the module for working with it, why I’ll tell you later.

Editing autorun:

 sudo nano /etc/rc.local 

Add in front of the exit line the following chown -R orangepi /sys/devices/platform/* . This command will make the orangepi user own the virtual files that are responsible for interacting with the GPIO port.

In theory, it would be better to create a group, assign rights, add a user to the group, but this is all a demonstration model (therefore, a character from a famous cartoon is recalled), and so it will come down. Of course, I do not in any way forbid you to do everything as it should.

Save the changes and reboot:

 sudo reboot 

Let's digress a bit on the hardware.

Atmega16u2

To transfer control, it was decided to use the Atmega16u2 microcircuit directly without the participation of unnecessary microcontrollers and ArduinoIDE, and run the executable code, you guessed it, right on the microcomputer.

Let us analyze the logic of the Arduin in the previous article.

The key values ​​were received via the serial port on the Atmega328p microcontroller (large oblong chip on Arduino UNO) which of the arrays specified in HIDKeyboard.h passed the key codes, so-called “USB HID keyboard keycodes” to the Atmega16u2 microcontroller (again on the serial port), which in turn sent via USB to the target computer. Serial → Atmega328p → Serial → Atmega16u2 → USB

In general, Atmega328p played the role of intermediary, and of course it is logical to remove it, which we will do, for this we will rewrite the code that was for Arduin under Orangepi, and connect Atmega16u2 directly.

Naturally bare chip will not work, you need at least a minimum binding.
I advise you to read the review at this link. For our purposes, the USB powered version is perfect


As you can see, the scheme is very simple, even a beginner can cope with it, not a lot of elements can be managed with hinged mounting, only it is better to fix the crystal oscillator so as not to dangle in the air. The generator by the way should be 16 megahertz if suddenly it is not clear from the scheme. And do not pay attention to the fact that the circuit for ATmega32u2 is suitable for ATmega16u2 and for ATmega8u2 too.

If there is an Arduino UNO board you can use it, you should connect to the tx contacts - № 0, rx -№ 1 and preferably remove the Atmega328p mikruha so that it doesn’t consume any power and does not clog the serial port air.

I don’t need to remind you about the logical levels, everything is the same as in the previous article, the serial port Orange PI is similar to Raspberry PI running at 3.3 volts and matching of voltages is necessary.

For ATmega16u2 firmware, you need to close the Reset leg with the ground for a second and fill the firmware with the Flip program

I will not describe in detail, it was already the last time. At this training is over let's get to the point.

We write the program

For the transfer of keys and remote control of the converter, we will write a small program.

Theory

At first there was a rush to simply port the sources from UNO-HIDKeyboard-Library, this is the library for the Arduino IDE (files HIDKeyboard.cpp and HIDKeyboard.h) that was used last time, but the functionality was not enough for the idea, so why not write your own program.

I present to your attention the Linux-Remote-HIDKeyboard, the name is so-so, but you also need to call it something, hereinafter referred to as LRHIDKeyboard.cpp or rkeysend (compiled binary).

The source will consist of 2 files LRHIDKeyboard.cpp and HIDKeyboard.h. HIDKeyboard.h is the same header file from the UNO-HIDKeyboard-Library library. Arrays are stored in this file to convert to “USB HID keyboard keycodes”, but I took the liberty of correcting errors and expanding arrays, compatibility with HIDKeyboard.cpp is preserved, so if needed, you can also use it for arduin.

USB HID keyboard keycodes are key codes delivered via USB, you can read more here (pdf).

In the HIDKeyboard.h header file, two arrays are the first to define regular keys, the second is for keys with the shift pressed. The decimal number obtained when capturing from the terminal is compared with the number of the array element and is replaced with this element that looks something like “0x7f” (hexadecimal number). Example key "a" has the value "4" in decimal notation or "04" in hexadecimal, key "ESCAPE" "41" in decimal or "29" in hexadecimal, a hexadecimal number indicating the press of any key is sent to the chip.

Practice

Open the console Orangepi create a directory where the program will be stored like this:

 cd ~ mkdir PROG cd PROG 

We create the files HIDKeyboard.h and LRHIDKeyboard.cpp :

 touch HIDKeyboard.h touch LRHIDKeyboard.cpp 

Open in the editor HIDKeyboard.h:

 nano HIDKeyboard.h 

Copy the contents of the listing:


save Ctrl + x, y, Enter

And again:

 nano LRHIDKeyboard.cpp 

Copy the contents of the listing:


Save Ctrl + x, y, Enter.

Compile

 g++ LRHIDKeyboard.cpp -o rkeysend -lncurses 

rkeysend is the name of the executable file obtained during the compilation process.
The -lncurses connection when compiling the ncurses library is used to capture the keys in the terminal and send text messages to the same terminal.

If the compilation was successful, you can proceed to the GPIO ports.

Converter control

A “freshly compiled” program can not only transfer keys, but also control the converter. I will explain why. First, you can adjust the image, brightness, contrast, sharpness, etc. Secondly, I already wrote about the resolution of the image obtained from the converter = 720x576. So, the converter has a mode of displaying only a part of the image, while the resolution does not change, in other words, you can see more fine details of the image using this mode.

The converter will be controlled by GPIO. GPIO, as you already know, general-purpose input / output, or if in Russian, I liked the rather accurate definition from Wikipedia “general purpose input / output interface”, which is a microcomputer's way of interacting with the outside world.

Connecting Orangepi PC to the converter

And so we Connect the converter with GPIO. The converter has physical control buttons: left, right, bottom, top, menu, and zoom. They are connected by the following principle as in the picture. The illustration shows only the principle of the buttons.


The converter has a port on which it measures the voltage and, in accordance with the required level, performs the action: opens the menu, enlarges the image, moves the image, etc.

To control the buttons I used bipolar transistors with optical input AOT128A:


The emitter and collector of the transistor are soldered to the ground and the contact of the button. The cathode of the transistor is connected (soldered) to the ground. The anode of the transistor is connected to the desired GPIO port via a 33 Ohm resistor.


If you change something, remember:

The control voltage at the anode of this transistor is not more than 1.6V; when this value is exceeded, the transistor starts to heat up strongly and thermal breakdown can occur. The power source for Orangepi and for the converter is desirable to use the same, otherwise the picture may change due to the potential difference.

We connect the transistor anodes to the following GPIO ports: PA14 - menu, PD14 - zoom, PC4 - top, PC7 - bottom, PG8 - left, PA21 - right.

The serial port for connecting the ATmega16u2 microcircuit is located on Ports 11 (RX) and 13 (TX). We connect as indicated in the image

Well, now everything is connected. At first, I wanted to control the converter on a single field-effect transistor using a single port, but somehow I didn’t ask, the PWM ripple is transmitted to the transistor and as a result, the resistance starts to float on it, there are options for smoothing filters, but this would greatly complicate the design. There is also an option to use a digital potentiometer via SPI or I2C, here everything is in your hands, dare.

Launch

Check whether everything is connected as it should:

1. Orangepi GPIO to Converter
2. Converter for VGA to Computer (slave)
3. AV output converter to AV input video capture card
4. Video capture card to USB Orangepi
5. Orangepi to ATmega8U2 / 16U2 / 32U2 microcircuit
6. ATmega8U2 / 16U2 / 32U2 chip via USB to computer (slave)
7. Computer (master) on SSH to Orangepi

Run the program

Ha Orangepi we launch the compiled program, there should appear the inscriptions with the indication of the open serial port and key combinations. Something like that.



There are keyboard shortcuts to call the Task Manager or change the layout, for example, to press the Ctrl + Alt + Del computer under your control in the terminal, enter “Alt + Del”, possible combinations are written when the program starts on top of the terminal window.

The video, as in the previous article, transmits motion, available at orangepi:8081 . Well, that's all, all the necessary information for repeating the experience is stated, the mission is completed.

Let's sum up:

Video transfer

The video remains very low quality due to the fact that it is transmitted via the AV input, but now we have remote control of the converter and if you select the desired item in the menu - you can watch the screen in parts in the same resolution.

There are possible solutions to the problem with video quality, only they have one major drawback: the price:

1. Velocap U2m usb 2.0 hdmi
2. UVC USB 3.0 HDMI

I did not try these options, for it is expensive, maybe someone from reading the article will risk.
You can probably save money on the microcomputer board by changing the Orangepi PC to the Orangepi one or Orangepi Zero, its cost is about 500 rubles. But there may be problems with Orangepi Zero, there is a different processor, respectively, another distribution with a different core, in which the necessary drivers and modules may not be available.

Cost price

VGA to AV Converter about 700rub.
The video capture card is about 500 rubles.
Orangepi PC about 1000 rub.
ATmega8U2 / 16U2 / 32U2 approximately 150rub.

Total: 2350 rub.

Well, this article came to an end, thanks to everyone who read it. I hope in practice you will succeed. Although I was not able to implement all of my plans, the result was interesting, especially for such a price.Of course, the resulting device needs some work, but I think it still has a right to exist. I give all my work as it is, without any guarantees, in good hands. Thanks for attention!