I am trying to create a simple version of VFH (Vector Field Histogram) on the NXT using NBC (next byte code). To do this I need to accurately measure the distance between the robot and an object. Since the NXT can show the distance in centimeters, I want to program the distance in centimeters in my program? Since there is no default centimeter reading(or is there?), can this be done or do I have to use the default sensor values? If it can, how do I do it? If not, how can I translate the ultrasonic sensor readings into centimeter readings?
Thanks in advance.
The default output is a byte value giving you centimeters.
task main(){
int DistanceInCm;
SetSensorLowspeed(IN_4);
while(true){
DistanceInCm = SensorUS(IN_4);
//do something with the value here.
Wait(800); //or just wait.
}
}
It's as simple as that. The sensor reading is a byte (0-255 cm). But the NXC compiler casts it into an into an int on the fly.
Note, though that the sensor is not very accurate! Especially if you read it while moving. So expect a lot of errors and noise in the readings.
Related
I want to get the temperature from a thermistor, so I made a voltage divider (3.3V to 10k resistor and between ground a 10k thermistor) I read the ADC between the 10k resistor and the thermistor.
The BCOEFFICIENT is 3977, the NOMINAL TEMPERATURE is 25C and I use the simple B parameter equation. I'm not sure where I'm doing mistake, I read room temperature as 10.5C which was suppose to be around 24C. The following is the part of the program that I used for temperature sensor(developed in AVR studio),
#define TEMPERATURENOMINAL 25
#define TERMISTORNOMINAL 10000
#define BCOEFFICIENT 3977
#define SERIESRESISTOR 10000
{
float ke1,tempa,xin
ke1 = adc_get_value(peak_adc2,peak2);
xin=(1023/ke1)-1;
xin=SERIESRESISTOR/xin;
tempa=xin/TERMISTORNOMINAL;
tempa=log(tempa);
tempa/= BCOEFFICIENT;
tempa+=1.0/(TEMPERATURENOMINAL + 273.15);
tempa=1.0/tempa;
tempa-=273.15;
dip204_set_cursor_position(1,3);
//sprintf(ui, "Temp is %.2f deg", Ref);
sprintf(ui, "Temp is %.2f deg", tempa);
dip204_write_string(ui);
}
I checked the voltage using multi-meter for instance in between the thermistor and 10k resistor and in the EVK 1100 using the following line
ke1 = adc_get_value(peak_adc2,peak2)*3.3/1024;
I get the same voltage in both.
Not sure where I'm doing a mistake, Hope someone guide me in right direction
Your code looks correct to me, and I suspect a hardware problem may be the culprit.
It seems likely you have inadvertently connected two 10K-ohm pull-up resistors between the ADC input and the +3.3V reference: perhaps one is already populated on the EVK1100 board, and you have added another one externally connected to your thermistor. This would be equivalent to putting both 10K-ohm resistors in parallel with each other, which would be equivalent to a 5K-ohm resistor in series with the thermistor. At 25°C, the thermistor resistance Rt would read 10K ohms, which would produce a voltage of:
+3.3V * (Rt / (Rt + 5K))
= 2.20V
instead of the correct +1.65V. This number is very close to the result you are seeing (+2.17V # 24°C).
You can verify this hypothesis by looking at the schematic and/or PCB for the EVK1100 to see if a 10K-ohm pull-up resistor is connected from the ADC input to +3.3V. If this is the problem, remove one of the two resistors and you should see correct behavior.
I clearly see the need to deepen my knowledge in RenderScript memory allocation and data types (I'm still confused about the sheer number of data types and finding the correct corresponding types on either side - allocations and elements. (or when to refer the forEach to input, to output or to both, etc.) Therefore I will read and re-read the documentation, which is really not bad - but it needs some time to get the necessary "intuition" how to use it correctly. But for now, please help me with this basic one (and I will return later with hopefully less stupid questions...). I need a very simple kernel that takes an ARGB Color Bitmap and returns an integer Array of gray-values. My attempt was the following:
#pragma version(1)
#pragma rs java_package_name(com.example.xxxx)
#pragma rs_fp_relaxed
uint __attribute__((kernel)) grauInt(uchar4 in) {
uint gr= (uint) (0.2125*in.r + 0.7154*in.g + 0.0721*in.b);
return gr;
}
and Java side:
int[] data1 = new int[width*height];
ScriptC_gray graysc;
graysc=new ScriptC_gray(rs);
Type.Builder TypeOut = new Type.Builder(rs, Element.U8(rs));
TypeOut.setX(width).setY(height);
Allocation outAlloc = Allocation.createTyped(rs, TypeOut.create());
Allocation inAlloc = Allocation.createFromBitmap(rs, bmpfoto1,
Allocation.MipmapControl.MIPMAP_NONE, Allocation.USAGE_SCRIPT);
graysc.forEach_grauInt(inAlloc, outAlloc);
outAlloc.copyTo(data1);
This crashed with the message cannot locate symbol "convert_uint". What's wrong with this conversion? Is the code otherwise correct?
UPDATE: isn't that ridiculous? I don't get this "easy one" run, even after 2 hours trying. I still struggle with the different Element- and variable-types. Let's recap: Input is a Bitmap. Output is an int[] Array. So, why doesnt it work when I use U8 in the Java-side Out-allocation, createFromBitmap in the Java-side In-allocation, uchar4 as kernel Input and uint as the kernel Output (RSRuntimeException: Type mismatch with U32) ?
There is no convert_uint() function. How about simple casting? Other than that, the code looks alright (assuming width and height have correct values).
UPDATE: I have just noticed that you allocate Element.I32 (i.e. signed integer type), but return uint from the kernel. These should match. And in any case, unless you need more than 8-bit precision, you should be able to fit your result in U8.
UPDATE: If you are changing the output type, make sure you change it in all places, e.g. if the kernel returns an uint, the allocation should use U32. If the kernel returns a char, the allocation should use I8. And so on...
You can't use a Uint[] directly because the input Bitmap is actually 2-dimensional. Can you create the output Allocation with a proper width/height and try that? You should still be able to extract the values into a Java array when you are finished.
I know that there is a lot in internet (http://forum.arduino.cc/index.php?topic=159557.0 for example) about OV7670 and I read a lot about it, but seems something is missing.
First of all I took a look into the way how can we read pixel by pixel from the camera to build the rectangular 600 X 480 image, and this was quite easy to understand considering HREF, VSYNCH and PCLOCK described on documentation here: http://www.voti.nl/docs/OV7670.pdf. I understand XCLOCK as an input I need to give to OV7670 as a kind of cycle controller and RESET would be something to reset it.
So at this point I thought that the functionality of such camera would be covered by wiring the following pins:
D0..D7 - for data (pixel) connected to arduino digital pins 0 to 7 as INPUT on arduino board
XCLK - for camera clock connected to arduino digital pin 8 as OUTPUT from arduino board
PCLK - for pixel clock connected to arduino digital pin 9 as INPUT on arduino board
HREF - to define when a line starts / ends connected to arduino digital pin 10 as INPUT on arduino board
VSYCH - to define when a frame starts / ends connected to arduino digital pin 11 as INPUT on arduino board
GRD - groud connected to arduino GRD
3V3 - 3,3 INPUT connected to arduino 3,3v
RESET - connected to arduino RESET
PWDN - connected to arduino GRD
The implementation for such approach from my point of view would be something like:
Code:
for each loop function do
write high to XCLK
if VSYNCH is HIGH
return;
if HREF is LOW
return;
if lastPCLOCK was HIGH and currentPCLOCK is LOW
readPixelFromDataPins();
end for
My readPixelFromDataPins() basically read just the first byte (as I'm just testing if I can even read something from the camera), and it is written as follows:
Code:
byte readPixelFromDataPins() {
byte result = 0;
for (int i = 0; i < 8; i++) {
result = result << 1 | digitalRead(data_p[i]);
}
return result;
}
In order to check if something is being read from the camera I just print it to the Serial 9600, the byte read from data pins as a number. But currently I'm receiving only zero values. The code I'm using to retrieve an image is stored here: https://gist.github.com/franciscospaeth/8503747.
Did somebody that makes OV7670 work with Arduino already figure out what am I doing wrong? I suppose I'm using the XCLOCK wrongly right? What shall I do to get it working?
I searched a lot and I didn't found any SSCCE (http://sscce.org/) for this camera using arduino, if somebody have it please let me know.
This question is present on arduino forum (http://forum.arduino.cc/index.php?topic=211741.0) too.
your idea is not bad but ...
the xclock need to be a clock (in your program is just a transition from 0 to 1 and is freezing there)
you need also to use I2C with SIOC and SIOD for configuring the camera (or you can use the default settings, but I am not sure if is the correct output format for you, 30F/s,VGA, YUV format ....)
your code execution is slower using the serial output in the same loop with reading data
I will recommend you to toggle the xclock pin and to move the pixel print in a if(). Also you will be able to read Data only in a very precise time, if you want to read only one byte, than after a transition from 0 to 1 of HREF you need to wait for a new transition from 0 to 1 of PCLK (you will be able to see only one 0-1 transition of HREF after 784x2 transitions of PCLK, (640 active pixels + 144 dead time for each line) x 2 (for YUV or RGB are 2 bytes received for each pixel) )
Hello I am Mr_Arduino from the arduino forums. Your issue is that you are reading pixels too slow please do not use digital read to do such a thing. Also if you insist on using a separate function just to read a byte make sure the function is being inlined. You can do this by declaring your function as static inline. Also as mentioned above how are you generating the clock. You can generate the XCLK using PWM on the arduino.
I have created a working example here:
https://github.com/ComputerNerd/arduino-camera-tft/blob/master/captureimage.c
Edit: a 3rd party has copied part but not all of the code from the above link into the answer here. However, the link must remain as the code posted below requires additional files from that source to actually work.
Edit 2: Removed irrelevant code. You will need to modify what you do with the data.
void capImg(void){
cli();
uint8_t w,ww;
uint8_t h;
w=160;
h=240;
tft_setXY(0,0);
CS_LOW;
RS_HIGH;
RD_HIGH;
DDRA=0xFF;
//DDRC=0;
#ifdef MT9D111
while (PINE&32){}//wait for low
while (!(PINE&32)){}//wait for high
#else
while (!(PINE&32)){}//wait for high
while (PINE&32){}//wait for low
#endif
while (h--){
ww=w;
while (ww--){
WR_LOW;
while (PINE&16){}//wait for low
PORTA=PINC;
WR_HIGH;
while (!(PINE&16)){}//wait for high
WR_LOW;
while (PINE&16){}//wait for low
PORTA=PINC;
WR_HIGH;
while (!(PINE&16)){}//wait for high
WR_LOW;
while (PINE&16){}//wait for low
PORTA=PINC;
WR_HIGH;
while (!(PINE&16)){}//wait for high
WR_LOW;
while (PINE&16){}//wait for low
PORTA=PINC;
WR_HIGH;
while (!(PINE&16)){}//wait for high
}
}
CS_HIGH;
sei();
}
You can also find it on github.
You can use my instruction: how to retrieve image from ov7670 It contains all the steps you need. There is also instuction to setup FrameGrabber: how to run framegrabber
For example, there are QR scanners which scan video stream in real time and get QR codes info.
I would like to check the light source from the video, if it is on or off, it is quite powerful so it is no problem.
I will probably take a video stream as input, maybe make images of it and analyze images or stream in real time for presence of light source (maybe number of pixels of certain color on the image?)
How do I approach this problem? Maybe there is some source of library?
It sounds like you are asking for information about several discreet steps. There are a multitude of ways to do each of them and if you get stuck on any individual step it would be a good idea to post a question about it individually.
1: Get video Frame
Like chaitanya.varanasi said, AVFoundation Framework is the best way of getting access to an video frame on IOS. If you want something less flexible and quicker try looking at open CV's video capture. The goal of this step is to get access to a pixel buffer from the camera. If you have trouble with this, ask about it specifically.
2: Put pixel buffer into OpenCV
This part is really easy. If you get it from openCV's video capture you are already done. If you get it from an AVFoundation you will need to put it into openCV like this
//Buffer is of type CVImageBufferRef, which is what AVFoundation should be giving you
//I assume it is BGRA or RGBA formatted, if it isn't, change CV_8UC4 to the appropriate format
CVPixelBufferLockBaseAddress( Buffer, 0 );
int bufferWidth = CVPixelBufferGetWidth(Buffer);
int bufferHeight = CVPixelBufferGetHeight(Buffer);
unsigned char *pixel = (unsigned char *)CVPixelBufferGetBaseAddress(Buffer);
cv::Mat image = cv::Mat(bufferHeight,bufferWidth,CV_8UC4,pixel); //put buffer in open cv, no memory copied
//Process image Here
//End processing
CVPixelBufferUnlockBaseAddress( pixelBuffer, 0 );
note I am assuming you plan to do this in OpenCV since you used its tag. Also I assume you can get the OpenCV framework to link to your project. If that is an issue, ask a specific question about it.
3: Process Image
This part is by far the most open ended. All you have said about your problem is that you are trying to detect a strong light source. One very quick and easy way of doing that would be to detect the mean pixel value in a greyscale image. If you get the image in colour you can convert with cvtColor. Then just call Avg on it to get the mean value. Hopefully you can tell if the light is on by how that value fluctuates.
chaitanya.varanasi suggested another option, you should check it out too.
openCV is a very large library that can do a wide wide variety of things. Without knowing more about your problem I don't know what else to tell you.
Look at the AVFoundation Framework from Apple.
Hope it helps!
You can try this method: start by getting all images to an AVCaptureVideoDataOutput. From the method:captureOutput:didOutputSampleBuffer:fromConnection,you can sample/calculate every pixel. Source: answer
Also, you can take a look at this SO question where they check if a pixel is black. If its such a powerful light source, you can take the inverse of the pixel and then determine using a set threshold for black.
The above sample code only provides access to the pixel values stored in the buffer; you cannot run any other commands but those that change those values on a pixel-by-pixel basis:
for ( uint32_t y = 0; y < height; y++ )
{
for ( uint32_t x = 0; x < width; x++ )
{
bgraImage.at<cv::Vec<uint8_t,4> >(y,x)[1] = 0;
}
}
This—to use your example—will not work with the code you provided:
cv::Mat bgraImage = cv::Mat( (int)height, (int)extendedWidth, CV_8UC4, base );
cv::Mat grey = bgraImage.clone();
cv::cvtColor(grey, grey, 44);
I would like to know if anyone knows how to perform a cross-correlation between two audio signals on iOS.
I would like to align the FFT windows that I get at the receiver (I am receiving the signal from the mic) with the ones at the transmitter (which is playing the audio track), i.e. make sure that the first sample of each window (besides a "sync" period) at the transmitter will also be the first window at the receiver.
I injected in every chunk of the transmitted audio a known waveform (in the frequency domain). I want estimate the delay through cross-correlation between the known waveform and the received signal (over several consecutive chunks), but I don't know how to do it.
It looks like there is the method vDSP_convD to do it, but I have no idea how to use it and whether I first have to perform the real FFT of the samples (probably yes, because I have to pass double[]).
void vDSP_convD (
const double __vDSP_signal[],
vDSP_Stride __vDSP_signalStride,
const double __vDSP_filter[],
vDSP_Stride __vDSP_strideFilter,
double __vDSP_result[],
vDSP_Stride __vDSP_strideResult,
vDSP_Length __vDSP_lenResult,
vDSP_Length __vDSP_lenFilter
)
The vDSP_convD() function calculates the convolution of the two input vectors to produce a result vector. It’s unlikely that you want to convolve in the frequency domain, since you are looking for a time-domain result — though you might, if you have FFTs already for some other reason, choose to multiply them together rather than convolving the time-domain sequences (but in that case, to get your result, you will need to perform an inverse DFT to get back to the time domain again).
Assuming, of course, I understand you correctly.
Then once you have the result from vDSP_convD(), you would want to look for the highest value, which will tell you where the signals are most strongly correlated. You might also need to cope with the case where the input signal does not contain sufficient of your reference signal, and in that case you may wish to (for example) ignore values in the result vector below a certain level.
Cross-correlation is the solution, yes. But there are many obstacles you need to handle. If you get samples from the audio files, they contain padding which cross-correlation function does not like. It is also very inefficient to perform correlation with all those samples - it takes a huge amount of time. I have made a sample code which demonstrates time shift of two audio files. If you are interested in the sample, look at my Github Project.