I have a LED stripe with a classic IR controller (image) and asked myself if I could control it with my Samsung Galaxy s21 Ultra which can emit infra-red light for its ToF camera. Now there are two issues.
Does Samsung provide an API access to control this IR emitter? (The remote control apps I downloaded all say that the phone doesn't have the necessary hardware (IR) for this)?
Is it physically possible, would the IR beam be even strong enough to control the LED stripe driver?
This is unlikely. The ToF IR pulse has to be very specific in length and shape, and likely controlled at the very low level (possibly by the sensor hardware itself).
So it's not likely that there's a way to customize the pulse shape or duration.
Well, it might be possible to turn the IR emitter on and off via some api (maybe the standard camera2 API or a special Samsung API) but IR transmitters commonly use a transmitting protocol which requires quite fast switching. That might be difficult.
There is some fairly detailed information about some IR Remote control protocols here: Data Formats for IR Remote Control from Vishay Semiconductors
I have seen projects which use the headphone socket of older phones connected to an IR LED to emit RC commands by outputting the signal as Audio.. pretty neat.
Related
I know every device transmits bluetooth at a different frequency. Any way to change the frequency. I want to change the frequency of BLE specifiaclly.
Given that the radio technology used in Bluetooth Low Energy is known as frequency hopping the answer is NO not as a developer as that belongs to the BLE driver level.
Realize that the range frequencies used to communicate between devices are collectively grouped into channels and that Bluetooth can switch between channels at 1600 hops per second so the notion of a third-party app being able to modify a lower level protocol seems undesirable as simply a security and separation of concerns matter.
Update
is it possible to change it at a device level. when i add a Bluetooth component(peripheral) to the device
Without more detail as to what and how you want to change the radio, I can't say. However:
What if I'm building the device from scratch
You'll need to learn how to read a datasheet which is provided by the chip/peripheral manufacturer. The datasheet will provide detailed physical connection information and details about the wire/software protocols necessary for operation. The datasheet for a chipset is roughly the API to the hardware, generally obtainable by using your favorite search tool, so if you do have a specific modification in mind, the datasheet should inform what is possible or not.
At this point you are at a level below the types of programming questions that StackOverflow normally operates at and should look to: https://arduino.stackexchange.com/ or https://raspberrypi.stackexchange.com/ or https://electronics.stackexchange.com/
I'm working on an Augmented Reality (AR) demo in which high quality openGL renders (in C++) will be generated from a PC and then streamed to an Android display device (running minimum Android 2.2). What is the easiest way to achieve this in real-time (30 FPS on Android Device) ?
I've looked into existing Anrdroid applications, and have not found anything to be suitable so far. The best available were remote desktop applications (such as TeamViewer) however the frame rates were far too low and unreliable.
Possible solution A:
1) Encode openGL window as H.264 Video (natively supported by Android)
2) Stream the H.264 Video via RTSP using a server
3) View the content from an Android Browser (android and pc connected via WiFi)
Possible solution B:
1) Encode openGL window as IP Camera in c++ (is this possible?)
2) Use an IPCamViewer on Android device to view (again connected via WiFi)
I'm not entirely sure if either or both of these approaches are viable and would like some reassurance before moving forward.
What is the resolution of the image (is it equal to the current screen resolution, larger or smaller)? It is possible and efficient to transport a H.264 stream, but it also depends on the machine used to do the encoding. Hardware encoders or GPU-accelerated encoders are your best bet.
Remember - if you choose to go with encoding, you will have latency due to buffering (on the encode and the decode side). It will be a constant time offset so if that's not a problem you should be ok.
The total system delay as proposed by this paper is composed of
Note that none of these delays can be fully measured directly in frame-time. Some of these depend on the frame data and/or the encoder/processing performed. But as a rough estimate with fast GPU-encoding and hardware decoding I'd say a lag of around 5-20 frames. You'll have to measure the final latency per-scenario. I did this by sending frames containing text (ticks) and once the frames were steady, comparing them side-by-side. In fact, I even allowed the user to enter "test mode" at anytime to compensate for network traffic peak times or have him change the "quality" settings to tweak this delay.
If someone wants to write a android application that interacts with a physical device, specifically a reader using mobiles audio jack
(e.g. Like how Square Inc is doing ) how is this done?
Is there a api's to interact with the reader and get the cards data?
When a company creates a reader (physical device) does it provide relevant apis?
Are the physical details abstracted from the application programmer?
I have found the AudioRecord class which can record magnetic stripe data from audio jack
But I can't fiqure out how to capture the actual card swipe event and
to extract the meaningful data from RAW DATA
Can any one help me with this
Any input is highly welcome!
The way this usually works is by encoding the data signal sent out by the device, like the card reader, in such a way that is can be decoded on the other end. Sound is a wave, and different amplitudes correspond to different loudness, and different frequencies correspond to different pitches. Imagine you have a sine wave, that varies between a high and a low frequency that are sufficiently different from each other so as to be easily distinguishable. The device sending out binary data (0's and 1's) can translate this data into an audio signal that varies by frequency (an alternative is varying amplitude). The receiver, in this case the mobile device, decodes the signal back into 0's and 1's. This is called "Frequency-shift-keying" (check out more here: http://en.wikipedia.org/wiki/Frequency-shift_keying).
The simplest way to implement this is to try and find an open library that already does it. The device sending the data will also need to contain some kind of microcontroller that can perform the initial modulation. If you come across any good libraries, let me know, because I'm currently
looking.
To answer your question, companies do not generally provide APIs etc to perform this.
This may seem like a lot of extra work to convert a digital signal, into an audio signal, and back, and you're right. However, every mobile device has essentially the same headphone jack, whereas the USB port on an Android is drastically different from an iPhone's lighting connector, or the connector in previous iPhones. Sending wirelessly through a network or Bluetooth is also an option, but they have their disadvantages as well.
Now the mobile device must be using a special headphone jack that supports microphones, otherwise it cannot receive input, it can only output sound. Most smartphones can do this.
Radios work on this principle (FM = Frequency modulation, AM = amplitude modulation).
Old dial up modems used FSK, which is why you heard those weird noises each time it connected.
Hope that helps!
I'm looking in to making a pH tester for my Android phone. I've found a pH electrode that will send a milliVolt signal which I can then use to convert into a pH reading (59.2 mV per pH unit # 25° C). The question I'm having is would it be possible to connect the electrode to the headphone jack and directly read the milliVolt reading or would I need to convert the analog signal to digital first and then plug it in via USB? I'm not a big electronics guy but I'm doing this project on the side and hoping to learn from it.
I was thinking perhaps getting the mV reading from the headphone jack would be possible with the GetMaxAmplitude function like from this thread here: Range of values for GetMaxAmplitude. Although, from what I understand the lowest reading possible with this function is 0 and there are negative mV values that can be read when testing for pH.
Any help is greatly appreciated, thanks!
This should be asked in the electrical engineering site. But the best way is to use a Bluetooth-to-serial converter, ($5 off ebay) and a PIC microcontroller with USART and A/D converter, ($1), you could program the PIC quite easily in C with the 'MPLAB' IDE and 'HI-TECH' C compiler. The tools you'll need are a PIC programmer ($20) and something with a serial port if you want to configure the Bluetooth-serial converter, like a desktop PC or a USB-serial converter. You might need an op-amp circuit to amplify the signal so it's readable by the PIC. You'd then use code from Google's BluetoothChat example to get your phone connecting to your bluetooth system, and receiving data from it.
Using a microphone for input would be tricky, for one reason, because it will be filtered to accept only AC. One way to get round that would be to modulate an oscillator's output so its amplitude is proportional to the DC signal you're measuring, then you could measure the magnitude by analysing the data from the microphone.
Interfacing with USB is more difficult than it sounds, it would be harder to build something which would interface with that and measure millivolts, than with bluetooth, because the PIC processor you use for analog to digital sampling and USB client would in fact have to either act as USB host or USB OTG on a phone, which is far more complicated than being a USB peripheral.
I think you would have the most consistent operation across a range of android devices if you built a circuit which uses the voltage from the sensor to control the frequency of an audio oscillator, and measures the frequency with software on the phone.
It's not impossible that a direct connection and reading the amplitude would work, but the two problems are that the signal path may not be good all the way down to DC - there may be a minimum frequency that it can pass making it unsuitable for measuring constant voltages. And second, that the gain of the input channel may not be consistent from device to device or even over time, temperature, etc. There are possible workarounds such as circuits which alternately send the voltage upright and inverted, effectively modulating it to overcome minimum frequency limitations, or even alternate the actual reading with a reference voltage to help model the input gain.
But I'd probably recommend either the frequency modulation approach, or using a $20 embedded bluetooth module and going wireless. Either way, the sensor system is going to need its own small battery pack.
You can extract some power from the headphone jack by telling android to make some sound (and, I suppose, rectifying the output and storing it in a capacitor) - I've seen a bunch of jack-powered things do this. I wonder if the 2 ideas could go together? What if you modulated some audio out through the headphone jacks, through the sensor, then back into the mic? The pH reading should mess with the received sound in some kind of measurable way I'd expect?
My quest is if anyone knows how to create an Android app that can send electric charge through the device's headphone jack, like in this video iPocket_LED. The video shows an app for iPhone that controls a LED plugged into the headphone jack.
I want to know how to access the device to send an electric signal.
Sorry about my English, is not my language, I hope some one understand me
Many consumer devices which accept an external microphone will provide "plug-in power". This is a small voltage typically from 1 to 5 volts across two of the contacts in the microphone connection.
Apple and (most) Android devices are no exception. Most use a 4-conductor TRRS connection with the following pin-out:
TIP = left headphone out
RING = right headphone out
RING = ground
SLEEVE = mic in + plug-in power
The plug-in power is usually around 2V on smartphones and is supplied as +2V on the microphone (sleeve) conductor. The phone will only supply it if it detects that a microphone is in place, which it does by testing the resistance across Mic to Ground to see if it's consistent with a microphone's impedance - something like 200 to 5000 ohms impedance, and I hear the iphones can be very fussy with this and need very close to 1600 ohms.
This means the maximum power you could draw from this and still seem like a microphone would be pretty small - around 1.25 milliamps. There are some low powered microcontrollers or other devices you may be able to power with this.
Note that plug-in power may be a similar concept to "phantom power" as used in pro audio gear but it's a different and incompatible standard. "plug-in power" is what causes the tiny electret microphones in smartphone headsets to work without needing their own small battery.
As for how to actually exert control over your attached device from an app, that's getting into much more complicated electronics. Presumably it is possible if you use the left and/or right headphone out lines to send signals to the device.
You'll need to play some audio. A small amount of current flows anytime audio plays, that's what moves the tiny little speakers in your headphones. The voltage will vary with the level of the audio. It is also AC current, such that the frequency of the sound (pitch) affects the frequency of the AC cycle.
It is going to be difficult to integrate with a device using this approach, especially because of the AC current. You can determine the appropriate pitch to send the voltage you want, but most "devices" are probably going to want a +3.3v or +5v DC signal. You'll probably need to do an AC to DC conversion to make that work.
I believe there is a means to integrate with an Android device via the USB interface. That would probably be far better and easier. You could get yourself an Arduino kit with a built-in USB shield/controller, and build your device on top of that.
See External USB devices to Android phones?
Yes using both at the same time is possible as this is how phones are designed to work. In fact depending on which specific device you have, overriding the volume limit will also give you a bit more power.
The best bet as far as lowest possible loss would be active rectification: at the null point have it switch over to +2V and the rest of the time whichever is the highest peak gets rectified. Simple enough to use two dual MOSFETs and this should get you enough power to at least initialize a phone though probably not charge it.