I have a couple of Maginon SP-1E smart plugs which can be triggered remotely. I manage them through HA, but did not find a way yet to just read out the state of the switch. There is a command to switch on or off and a result is returned. The plug is running Busybox (v1.12.1 (2014-07-31 06:32:52 CEST) multi-call binary) and is somewhat stripped down, but telnet, ifconfig, nvram_get, nvram_daemon, nvram_set, flash, gpio are all binaries that are available for use.
To turn on:
http://192.168.0.52/goform/SystemCommand?command=GpioForCrond+1
Returns:
gpio_set_dir: gpio=2, dir=0
gpio_set_dir: gpio=1, dir=1
InitGpio() success, fd = 3
Get GPIO1 = [01]
To turn off:
http://192.168.0.52/goform/SystemCommand?command=GpioForCrond+0
Returns:
gpio_set_dir: gpio=2, dir=0
gpio_set_dir: gpio=1, dir=1
InitGpio() success, fd = 3
Get GPIO1 = [00]
So clearly there seems to be a way to toggle (and read) the switch state, but I cannot find a way to do so. Any hints? The source code for the plug is available here.
Related
I started using fmt for printing recently. I really like the lib, fast, easy to use. But when I completed my conversion, there are ways that my program can run that will render with a bunch of additional newlines. It's not every case, so this will get a bit deep.
What I have is a compiler and a build manager. The build manager (picture Ninja, although this is a custom tool) launches compile processes, buffers the output, and prints it all at once. Both programs have been converted to use fmt. The key function being called is fmt::vprint(stream, format, args). When the build manager prints directly, things are fine. But when I'm reading the child process output, any \n in the data has been prefixed with \r. Windows Terminal will render that fine, but some shells (such as the Visual Studio output window) do not, and will show a bunch of extra newlines.
fmt is open source so I was able to hack on it a bunch and see what is different between what it did and what my program was doing originally. The crux is this:
namespace detail {
FMT_FUNC void print(std::FILE* f, string_view text) {
#ifdef _WIN32
auto fd = _fileno(f);
if (_isatty(fd)) {
detail::utf8_to_utf16 u16(string_view(text.data(), text.size()));
auto written = detail::dword();
if (detail::WriteConsoleW(reinterpret_cast<void*>(_get_osfhandle(fd)),
u16.c_str(), static_cast<uint32_t>(u16.size()),
&written, nullptr)) {
return;
}
// Fallback to fwrite on failure. It can happen if the output has been
// redirected to NUL.
}
#endif
detail::fwrite_fully(text.data(), 1, text.size(), f);
}
} // namespace detail
As a child process, the _isatty() function will come back with false, so we fall back to the fwrite() function, and that triggers the \r escaping. In my original program, I have an fwrite() fallback as well, but it only picks up if GetStdHandle(STD_OUTPUT_HANDLE) returns nullptr. In the child process case, there is still a console we can WriteFile() to.
The other side-effect I see happening is if I use the fmt way of injecting color, eg:
fmt::print(fmt::emphasis::bold | fg(fmt::color::red), "Elapsed time: {0:.2f} seconds", 1.23);
Again Windows Terminal renders it correctly, but in Visual Studio's output window this turns into a soup of garbage. The native way of doing it -- SetConsoleTextAttribute(console, FOREGROUND_RED | FOREGROUND_GREEN | FOREGROUND_INTENSITY);-- does not trigger that problem.
I tried hacking up the fmt source to be more like my original console printing code. The key difference was the _isatty() function. I suspect that's too broad of a question for the cases where console printing might fail.
\r is added because the file is opened in text mode. You could try (re)opening in binary mode or ignore \r on the read side.
My audio system is simple: two speakers in the rear panel--front left(FL) ,front right(FR) ,headphone in the front panel. The primitive status is as below--primitive status:
In this status , sound can be heared from FL,FR,and headphone.
I find a strange fact that master,front,surround in alsamixer changed into MM status when to click M on LFE,i move the cursor on LFE,and click M,LFE changed into MM,at the same time master,front,surround all changed into MM status !No sound can be heared !
And i click M for the second time on LFE,all status changed as below:
Let's go on from the primitive status,and unplug line from rear panel,no sound in headphone! The status in alsamixer gui is as below:
Now re-plug the line in the rear panel,the status in alsamixer gui turns into :
Please give an explanation in detail.
To see what's going on:
In one terminal window, run alsactl monitor.
In another terminal window, run alsamixer.
As you mute/unmute things in alsamixer, you can see the control commands in the monitor window. You should see multiple switch commands show up when you mute the LFE.
The reason this is happening is because of the pulseaudio profile in use by alsamixer.
Profiles are located in /usr/share/pulseaudio/alsa-mixer/profile-sets/*.conf
Paths are located in /usr/share/pulseaudio/alsa-mixer/paths/*.conf
So which ones are in use? You can check that with pacmd info | grep "active", which may produce something like:
active port: <analog-output-speaker>
active port: <analog-input-headphone-mic>
active profile: <output:analog-stereo+input:analog-stereo>
Ok, so the output mapping is analog-stereo. I can find this in /usr/share/pulseaudio/alsa-mixer/profile-sets/default.conf. It contains the following:
[Mapping analog-stereo]
device-strings = front:%f hw:%f
channel-map = left,right
paths-output = analog-output analog-output-lineout analog-output-speaker analog-output-headphones analog-output-headphones-2
paths-input = analog-input-front-mic analog-input-rear-mic analog-input-internal-mic analog-input-dock-mic analog-input analog-input-mic analog-input-linein analog-input-aux analog-input-video analog-input-tvtuner analog-input-fm analog-input-mic-line analog-input-headphone-mic analog-input-headset-mic
priority = 10
The real control is under /usr/share/pulseaudio/alsa-mixer/paths/analog-output-speaker.conf. You can read /usr/share/pulseaudio/alsa-mixer/paths/analog-output.conf.common for details, where we see two important sections:
; When a device shall be muted/unmuted *all* elements listed in a path
; file with "switch = mute" will be toggled.
(there's a bit of a caveat to this one. It seems that unmuting does NOT toggle other elements in the path)
and
; [Element ...] # For each element that we shall control
...
; switch = ignore | mute | off | on | select # What to do with this switch: ignore it, make it follow mute status,
; # always set it to off, always to on, or make it selectable as port.
; # If set to 'select' you need to define an Option section for on
; # and off
...
So now, if we want to adjust an element such that it's always on, always off, or simply ignores muting, we would set the corresponding switch= values in the Element of interest.
If you want to adjust the behavior of the headphones when activating that path (i.e. when plugging them in), change the Element values in paths/analog-output-headphones.conf
We have a Linux device which has a speaker and MIC devices. These devices are shared among different modules - example a VOIP call can use speaker, a hazard Warning system can use speaker, a Voice prompt can use a speaker etc:
There seems to be a function in ALSA which uses pcm to provide the status.
int snd_pcm_status (snd_pcm_t * pcm, snd_pcm_status_t * status)
However the *pcm is returned by snd_pcm_open. We do not want to open the device as we would like to know the status of the device using its "name"
Alsa API is here
How can we check if a resource/device is busy without opening it and using its name?
The same information for playback stream X of device Y on card Z is available in the file /proc/asound/cardZ/pcmYp/subX/status; when the device is not open, it just says "closed".
Please note that you cannot use this information to decide if you can open the device, because some other process could have openend it just after you've read this information. The only way to check if you can open it is to actually try.
Though it requires /dev/dsp, this seems to work:
#!/bin/dash
## If the speaker is not used by any, returns 0, and prints "free"
## Otherwise, returns 1 and prints "not free"
iExit (){
trap '' 0
exit $1
}
iCatch (){
# The speaker is already in use
echo not free
iExit 1
}
trap iCatch 0
{
exec 3>&1 1>/dev/dsp
# If the execution reaches here, the speaker is not used by any
# Otherwise, it's catched by iCatch
exec 1>&3
echo free
iExit 0
} 2>/dev/null
Without PulseAudio, it seems on some PC only one output is accepted at one time; on others simultaneous playbacks are allowed. But even in the latter case, the above code works.
NB: The above code does not work with bash; for bash, simply use if/else rather than trap.
NB 2: /dev/dsp may be lacking depending on the kernel configuration.
The man page is here: http://man.cat-v.org/unix-6th/3/ttyn
This example:
if (ttyn(0) = 'x'){
...
}
The man page says "x is returned if the indicated file does not correspond to a
typewriter."
The indicated file would be argument 0, so the standardinput, right?
And what is a typewriter? My keyboard?
What are you checking with this line?
if (ttyn(0) = 'x')
At that point in time, a typewriter (or teletype, or tty) was an RS-232 terminal connected to the computer via a serial port. The device entries in /dev corresponding to these ports were named /dev/tty0, /dev/tty1, /dev/ttya, etc. Each of those files was a character special file, as opposed to an ordinary file.
When a terminal was detected by the system, typically by being turned on or connected through a modem, the init process opened the device on file descriptors 0, 1, and 2 in a new process, and those file descriptors persisted through the login process, a user's shell, and any processes forked from the shell.
As you said in your question, file descriptor 0 is also called standard input.
The ttyn function calls fstat on its argument, which returns some info about the file such as its inode number, permissions, etc. ttyn then reads through /dev, looking at each file that starts with "tty", to see which one has the same inode number as ttyn's argument. When it finds a match, it returns the 4th character of the filename, which would be '0', '1', 'a', etc. If no matches are found, it returns 'x'.
There were generally a console and a few 8-port serial interfaces on a PDP-11. so there was no ttyx. And you could name devices in /dev anything you wanted. So it was easy to avoid /dev/ttyx being an actual device.
Commands like goto could use ttyn(0) != 'x' to determine whether the user was actually typing the command on a terminal.
Here is the default config file, /etc/ttys, used by init in V6. The console was tty8.
In V7 Unix, the functionality of ttyn was replaced by ttyname, which could accommodate longer device names, and isatty, which returned true if the fle descriptor was a terminal device. The goto command was not present in V7.
I've never seen this library call before; I'm used to the more familiar ttyname. The webpage doesn't give a return value, but based on what the text says, it would give the last char value in the string returned by ttynam(3). So if stdin (fd0) was connected to "/dev/tty2", then the return value would be the char 2. And in C, you would be able to check it with:
if (ttyn(0) == '2') { ... }
Granted the documentation is not clear. And it is using bad terminology; instead of "typewriter", it should be using "teletype" or "terminal", which are the accepted terms. Remember that stdin can be different from stdout; it is perfectly possible to do run cat </dev/tty1 > /dev/tty2, assuming you have the permissions for it.
I'm using a serial device for a project, and what I'm trying to accomplish PC side, is listening for a command sent by the serial device, interpreting the query, running some code depending on the query, and transmitting back the result.
To be honest I tried out using PHP as the listener, and it works, unfortunately the infinite loop required to make the script act as a receiver, loads the CPU to 25%. So it's not really the best option.
I'm using cygwin right now, I'd like to create a bash script using linux native commands.
I can receive data by using:
cat /dev/ttyS2
And send a response with:
echo "command to send" > /dev/ttyS2
My question is, how do I make an automated listener to be able to receive and send data? The main issue I have, is actually how do I stop the cat /dev/ttyS2 command once information was received, put it into a variable which then I could compare with a switch, or a series of if else then blocks. Afterwards send back a response and start the cycle all over again?
Thanks
Is this not what you're looking for?
while read -r line < /dev/ttyS2; do
# $line is the line read, do something with it
# which produces $result
echo $result > /dev/ttyS2
done
It's possible that reopening the serial device on every line has some side-effect, in which case you could try:
while read -r line; do
# $line is the line read, do something with it
# which produces $result
echo $result > /dev/ttyS2
done < /dev/ttyS2
You could also move the output redirection, but I suspect you will have to turn off stdout buffering.
To remain fairly system independent, use a cross platform programming language: like Python, use a cross platform serial library like : pySerial and do the processing inside a script. I have used pySerial and I could run the script cross platform with almost no changes in source code. By using BASH you're limiting yourself a fair little.
If you use right tools, it is possible to actually have your CPU usage to be exactly 0 when your device does not have any output.
To accomplish this, you should use some higher level language (Perl, Python, C/C++ would do, but not bash) and use select loop on top of file handle of your serial device. This is an example for Perl http://perldoc.perl.org/IO/Select.html, but you can use any other language as long as it has support for select() syscall.
I would recommend to use C/C++ with Qt 5.1.1, it's really easy and if you are familiar with the framework it'll be a piece of cake!!!
Here you can find more information and here more helpful examples, give it a try,
it's really pain free!! Also you can develop on win and then port your code to linux...straight forward.
Declare an object like this:
QSerialPort mPort; //remember to #include <QtSerialPort/QSerialPort>
//also add QT += serialport to your .pro file
Then add this code:
MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
{
setupUi(this);
connect(this->pushButton,SIGNAL(clicked()),this,SLOT(sendData()));
mPort.setPortName("ttyS0");
mPort.setBaudRate(QSerialPort::Baud115200);
mPort.setParity(QSerialPort::EvenParity);
if(!mPort.open(QSerialPort::ReadWrite))
{
this->label->setText(tr("unable to open port, %1").arg(mPort.error()));
}
connect(&(this->mPort),SIGNAL(readyRead()),this,SLOT(readData()));
}
void MainWindow::sendData()
{
QByteArray data = lineEdit->text().toLatin1();
if(mPort.isOpen())
{
mPort.write(data);
}
else
{
this->label->setText(tr("port closed %1").arg( mPort.error()));
}
}
void MainWindow::readData()
{
QString newData;
int bread=0;
while(bread < mPort.bytesAvailable() ){
newData += mPort.readAll();
bread++;
}
this->textEdit->insertPlainText("\n" + newData);
}