I've got two Arduino/Xbees set up over a network and trying to send an analog voltage reading from one to the other. I'm sending the raw integer analog reading across (1-1028 reading) to be translated into a voltage on the second Arduino unit.
So question is - how do I unpack two bytes? I'm using byteHigh and byteLow commands to read the serial value and assembling these two with a Word function, but this isn't working properly. The Word turns out something completely unrelated to the actual analog V sent.
Am I missing something here?
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I am using esp8266 with Arduino framework to drive a LED matrix display and some sensors. The problem I encountered is as follows: when I want to read data from CO2 sensor (mhz-19b) I have to do so by sending a command via serial and then read the answer it gives me. This of course takes some time and causes a delay in my code which means the LED matrix display stops refreshing and goes dark for a short but noticable amount of time.
I have a smiliar problem with reading data from DHT22 temperature and humidity sensor (reading data takes some time and causes a delay in code).
Is there anyway I could solve this? Perhaps with some kind of pseudo-multithreading (if that even exists). Also would using esp32 (which is dual core) instead of esp8266 help?
I'm trying to do something really simple and I'm having a bit of trouble getting it to work. I'm working with the MPL3115A2 Altitude/Pressure Sensor and a pic32 uC32 board, and I'm trying to communicate between the two using I2C. (uC32 board is similar enough to arduino that it's practically the same in terms of coding).
I'm using the wire library and I'm simply trying to read register 0x0C from the MPL3115A2, which should give me the device ID.
Here's a code snippet (the define is at the top of the code and the rest is in the main loop):
#define barAddress 0x60
Wire.beginTransmission(barAddress);
Wire.send(0x0C);
Wire.endTransmission();
Wire.requestFrom(barAddress, 1);
uint8_t a = Wire.receive();
Serial.println(a, HEX);
So I start the transmission with address 0x60 (From the datasheet: The standard 7-bit I2C slave address is 0x60 or 1100000. 8-bit read is 0xC1, 8-bit write is 0xC0.). Then I send 0x0C because that's the register I want to access. I then end transmission, and request 1 byte from address 0x60, receive that bit into a 8-bit variable, then print it.
The problem I run into is that when I print it, I just get 0. I don't get the device ID, just 0. No matter what register I try to read, I get 0.
I've been banging my head against a wall for the past few days trying to get this to work. I've attached something I've captured with a logic analyzer, as well as a list of registers from the datasheet of the MPL3115A2 that I've been trying to access.
Using a logic analyzer I can see the clock and data lines. The clock seems normal and the data line gives me the following:
START
Write['192'] + ACK
'12' + ACK
STOP
START
Read['193'] + ACK
'0' + NAK
STOP
This all seems correct to me (192 and 193 come from 8-bit write and read being 0xC0 and 0xC1), except for the '0'. I should be getting the device ID, not 0.
Thanks for any help with this!
You should look at Freescale's app note AN4481, which is referred to by the datasheet. Page 5 shows the single-byte read operation which is what you are doing, except that the register address write must not be followed by a STOP but instead uses a REPEATED-START.
I'm not familiar with the Wire library but it look like all you need to do is remove the Wire.endTransmission(); between the send and requestFrom.
Hopefully, this will solve your problem.
I am using Arduino UNO board. I have 24 analog channel which gives me 0~5v analog out put. Now my problem is I have only 5 analog channel. I wanted to read value from each channel for every 2 min and then switch to other channel. Can anyone suggest me in Hardware how can get analog value ?
I am planning to use 8:1 multiplexer or 16:1 multiplexer . Will it is correct way of doing it. Can you suggest other way of doing it in hardware ?
74HC4051,74HCT4051,ADG708,MD14051B,
IC I am planning to Use.dep[end on so,s1,s2 just switch the channel
As a start, you might need to know that even Arduino Uno also have internal MUX. In my experience of reading multiple analog channel, this is the approach that I take. However by taking this approach, I suggest you to recheck the analog value so adding MUX will not generate any error or bias.
This could be done by comparing the output of measurement with the MUX and output of measurement without the MUX. I used 74HC4051 and it works brilliantly, just make sure not to leave any pin floating. The only disadvantage of this method is that you will need to use some I/O to control the MUX, but if that is not an issue for you, then go ahead.
Any other method could be more complicated. It would require your analog channels to correlate with each other, and you need to find a way method to combine multiple analog channel into a single channel.
e.g: if your aim is to compare two analog value, instead of measuring the value and comparing the value in software, you could make use of op-amp comparison circuit to compare the value for you and take the comparison result instead.
Use the photon-pixel coupling method, it is a new approach in science for sampling an unlimited number of sensors in parallel.
Basically, each sensor output is an LED. If you have 10000 sensors, the output of all of them is inserted in a LED array, a LED matrix as the authors say. After that, the LED array is filmed by a video camera and the images are processed in real time by a computer. A software reads one pixel from each LED from the LED array and converts it to numerical values. So, your LED array will be converted in a matrix (with 10000 elements) filled with numbers that can be processed as you wish in your software. I don't know if I was explicit but you can read their article here: https://www.sciencedirect.com/science/article/pii/S2215016119300901
Note that classic multiplexing is serial, this approach is parallel.
The photon-pixel coupling method is truly ingenious because it solves two main problems in engineering: an unlimited number of sensors and their parallel sampling at video rate frequencies. Just imagine, we can read as many sensors as we wish. What I wander is if we can adapt the photon-pixel coupling to Arduino. I am new in the world of microcontrollers but I know Arduino can support a cam, so it should be possible.
If you are a PhD student then:
P.A. Gagniuc, C. Ionescu-Tirgoviste, R.G. Serban, E. Gagniuc. Photon-pixel coupling: A method for parallel acquisition of electrical signals in scientific investigations. MethodsX, 6:968-979, 2019.
To read more analog channels than inputs you have, an analog multiplexer is a good option. All the ones you suggested will work, but personally, I like the Analog Devices ICs for analog circuits, so I would take the ADG708, but this is just a personal preference.
I'm trying to send an analog value from xbee to another xbee (WHICH IS CONNECTED TO ARDUINO). But I don't want to read this value serially (x=Serial.read();).
I would like to read this value from an arduino's analog input (x=analogRead(A0);). Can I pass an analog value from 1st xbee input pin to 2nd xbee output pin and connect this pin with ex.arduino's analog input (A0) and process it? If it can be done, how does this occur? (sorry for my english)
This is indeed possible. Xbee's have DAC and digital line support. Check out the user manual found in this Manual
The information you're going to need is on page 12. This is for series one xbee's.
For series two xbee's the process is different and can be found in this manual
manual on page 41. Good luck!
I would suspect you would be better off using xbee API and just do an AT command to read pin, then transfer it over serial TX out to the arduino RX in.
I have tried measuring the analog pin value using the provided standard sketch in the Arduino IDE. However even when there is no connection to the pin, it prints out random values. Is there anything that has to be taken care of?
I have a FSR sensor connected from 5V+ to analog pin 0
No connection giving you random value is completely expected. The pin is floating, and may or may not have a charge on it at any time, giving random values.
Attach the analog input to ground - it should return a number approaching zero (within the accuracy and noise of the ADC).
You have to use "Pull-up" or "Pull-down" resistor. Read here about this circuit: http://www.ladyada.net/learn/arduino/lesson5.html
Providing a path of higher resistance to ground ensures that when that portion of the circuit is open, the static electricity remaining in the portion connected to the pin gets grounded. It also splits the voltage between both paths to allow you to properly throttle the voltage to the pin.
The same problem arise to me ,
What you have to do is change the" Serial.begin(9600);"
To "Serial.beigin(115200);
Now it is showing exact zeroes without any input source.