I'm working with Arduino with a NFC Shield (this one). I'm trying to use interrupts on Rx: I want my Arduino to wake up, each it receives data on serial line. This works correctly without the NFC shield. However, with the NFC shield, it sends '0' on the serial port, triggering an interrupt, which I really don't want.
After some research, I discovered that each time the library writes on the SPI pins (like digitalWrite(_clk, LOW);, it returns '0'.
In the loop function, I have this line:
id = NFC.readPassiveTargetID(PN532_MIFARE_ISO14443A);
So, each time this line is executed, a '0' is sent through the serial bus, and the Arduino never goes into sleep mode... (even if there is no NFC card to read)
Does someone know why? And how can I avoid it?
Related
I'm trying to write a simple code that sends a string to an xbee and one that sends the string back, I was able to do this with XCTU via console, but I want my arduino to send the string.
I was able to use a simple code that read my output from the serial monitor and sends it to an xbee connected via usb adapter, the problem is that I now wrote the code so it sends a predefined string like in the screenshot, but when I write into the monitor it still sends whatever I wrote instead of the static string. I'm also unable to read what I type into the xbee console from XCTU.
I'd love any assistance in this, I've tried uploading and resetting everything to no avail.
Screenshot of problem with the current code of the arduino on the left
You said you were using an Arduino to try to communicate with your XBee Zigbee module.
One thing you have to check is the connection between the TX and RX signals on the Arduino side and on the XBee Zigbee side.
I've helped someone on another forum who used this Seed Studio XBee shield :
If you look at the schematics of this shield, the XBee 'DOut' signal (Tx) is wired to the XB_TX line which can be connected to any of the AJ2 pin with a jumper.
Now on the Arduino side :
On this extract of the Arduino schematics, we can see that the ATMEGA UART has it's RX signal connected to pin 2 of the CPU which is wired to the IOL (AJ2) pin 0.
So, that means that on this shield, the jumper have to be placed between XB_TX and pin 0 of AJ2 to connect the XBee transmission signal (output) to the ATMEGA reception signal (input) [and also XB_RX have to be connected pin 1 of AJ2].
As you didn't mention what kind of shield you were using, you have to double check this point which is a common issue when using serial communication.
In a general way, ALWAYS connect 1 output to N input (except open-drain or open-collector outputs which can be connected together to make a wired OR but which finally have to be connected to N inputs)
Hope this helps
Best regards
From what I can tell on the documentation Xbee "hijacks" the serial system. Instead try blinking an LED to confirm data is being received and sent.
documentation
I recently bought an Arduino UNO to read the data outputted by my Smart Meter. The meter uses serial communication and I would like to see the values being outputted on my laptop screen. I figured I would need to use the SoftwareSerial library to read the incoming data and print that data on my screen using the hardware serial and the Serial Monitor in the Arduino IDE. To become familiar with (software) serial communication on the Arduino, I reviewed the documentation of the SoftwareSerial library. Problem is, I can't get the most basic example to work and I have been stuck on this for quite a while now. The example code is below, the example can be found here
#include <SoftwareSerial.h>
SoftwareSerial mySerial(10, 11); // RX, TX
void setup() {
// Open serial communications and wait for port to open:
Serial.begin(57600);
while (!Serial) {
; // wait for serial port to connect. Needed for native USB port only
}
Serial.println("Goodnight moon!");
// set the data rate for the SoftwareSerial port
mySerial.begin(4800);
mySerial.println("Hello, world?");
}
void loop() { // run over and over
if (mySerial.available()) {
Serial.write(mySerial.read());
}
if (Serial.available()) {
mySerial.write(Serial.read());
}
}
As far as I understand this, the following should happen:
- Type text in Serial Monitor window.
- Serial.read() reads this data and writes it to the Software Serial.
- The Software Serial reads this data and writes it back to Serial.
- That which was written appears on the screen.
But whatever I try, nothing happens. Among things I tried to following:
- Change the baud rate for both software and hardware serial (9600 for instance).
- Tried a different SoftwareSerial library (AltSoftSerial).
- Tried different RX and TX pins for SoftwareSerial.
- Instead of Serial.write(mySerial.read());, store the result in a char first.
I'm probably missing something obvious. I would be grateful to anyone who could shed some light on this or offer an alternative way for me to read the data from my Smart Meter.
Edit
I had no wiring, because the example specified "There is no circuit for this example". I tried all three options suggested by #slash-dev, but none had the expected behaviour:
SoftwareSerial with wires connecting pin 1 to pin 10 and pin 0 to pin 11. It prints strange characters:
Goodnight moon!
Ùniÿhtÿmoÿn!ÿ
nihtmoÿttt
AltSoftSerial with wires connecting 1-8 and 0-9. First prints Goodnight moon! and then it keeps printing Ô당¥�¡Ñ�moon!.
NeoSWSerial with wires connecting 1-10 and 0-11. Same as AltSoftSerial but keeps printing Ôë‹–+ë¡Ñ�j½½¹…j.
The baud rates must be the same on Serial and mySerial.
And you don't describe the connections, so I have to ask: Did you connect a wire from pin 1 (Serial transmit) to pin 10 (mySerial receive), and another wire from pin 0 (Serial receive) to pin 11 (mySerial transmit)? Note how they are crossed.
AltSoftSerial is really the best choice, but it only works on pin 8 (RX) and pin 9 (TX), which would require connecting 8 to 1 and 9 to 0. SoftwareSerial is very inefficient, because it disables interrupts for long periods of time. This can interfere with other parts of your sketch or other libraries.
My NeoSWSerial library is another alternative. It's almost as efficient as AltSoftSerial, but it works on any two pins. It can transmit and receive at the same time (unlike SoftwareSerial), but it only works at bauds 9600, 19200 and 38400.
EDIT:
I think what you've tried is probably working ok. All the software serial libraries use interrupts for processing individual bits instead of one interrupt per character. When there are other interrupts in the system (millis() TIMER0 or Serial), the bit "calculations" can be affected. This manifests as receiving the wrong byte. Your loopback test makes it especially susceptible because the sending and receiving are synchronized (the initial receive interrupt occurs while the transmit interrupt is starting the next char).
If you just hook 0 to 1, I think it will work, because the UART is able to send and receive at the same time, and it deals with complete characters, not bits. The character interrupts do not disturb the sending or receiving of the bits.
In developing the NeoSWSerial library, I have seen this manifest the same way. I had to use two Arduinos to fully test asynchronously (i.e., not synchronized). In your case, using AltSoftSerial for the SmartMeter should work fine, and you can choose different baud rates. If you are echoing the SmartMeter characters to Serial, be sure you have a higher baud rate on Serial.
This is most likely not related to the issues now 5 years ago, but in my case I was using the Arduino IDE 2.0.0-rc5 which was not writing to the soft serial for unknown reasons. I downgraded to Arduino IDE 1.8.19 and the same serial sketch worked.
I am fighting with ESP8266 wifi module and connecting arduino. After updating firmware to newest version i started to programm arduino to get data incoming from wifi. I saw many examples about maiking webserver via ESP8266 but none of them works for me.
ESP is connected to my Arduino Leonardo:
>
Arduino -> ESP8266
power 3.3V -> vcc
ground -> ground
tx -> rx (via logic level converter 5->3.3V)
rx -> tx (via logix level converter
power 3.3V ->gpio0 (without any resistors)
I made simple sketch:
void setup(void){
Serial.begin(9600);
Serial1.begin(115200);
}
void loop() {
if(Serial1.available())
{
Serial.println("WIFI IS AVAILABLE");
Serial1.println("AT");
delay(1000);
} else {
Serial.println("WIFI not available.");
delay(1000);
}
}
After executing it ESP8266 is powered (red led is on) and also every second blue led (blinks). That makes me sure that in fakt "AT" command is transmited to module. But there are also two issues:
i want to get response from esp - in this case word "OK". I tried Serial1.read() but it only reads one byte. Serial1.readString() makes my messages "wifi not available" and sametimes "wifi is available" as if for a while the connection would be unavailable
after uploading sketch to arduino and having powered esp8266 wifi module is always unavailable - i need to power the module off and on again to have it working.
Anybody please can help me?
What you need to do is change your approach a bit. Do not check if data is available. The trick is to send the module something and then check for data.
Do something like:
while (Serial.available() > 0)
Serial.read();
to clear the buffer before any command you want to send. Then send the command. Then check for data as a response.
Do not rely on that Blue LED as any indication. It is only an indication that the ESP8266 is busy using the WiFi in some sort of way, whether it is doing keepalives, initializing WiFi or whatever. It can be totally unrelated to whatever you are sending. If you do not receive a valid response then you must assume that there is comms issues between you and the module. One thing though is that if that Blue LED never goes off then either the module has frozen or the firmware was corrupted. I have had that many times. I then reload the firmware and usually that fixes it. It usually only happens during development times where I reset, upload code or change wires.
I use mine with an atmega328 on a separate slef-built board and not the one on the Uno and run that board on 3.3v itself and then use a logic level converter between that atmega board and my Uno so that I can program it. But I have had sporadic issues with non-comms but I suspect it might be power related. Be aware that running your Serial via the logic level converter might also be causing comms issues.
Proposed wiring: All pins except RX,TX,VCC and GND goes to VCC via 10K pullup resistors. RX goes to the arduino's TX and TX goes to the arduino's RX. Of course you know where VCC and GND goes.
Is possible for Arduino to receive a 5V into a inputPin from a external battery?
If I have a system that has it's own power supply and after an event fires 5V. How can Arduino read this input?
This is an electrical problem, no software issue I presume.
Here is how to proceed:
1) Make sure both boards have the same ground (connect GND together and make sure there is no conflict)
2) Connect your output to an input on the Arduino board (pin 2 e.g.). This connection is preferably done using a resistor, 1 kOhm will be ok.
On software side, just set this pin as input pinMode(2,INPUT); in setup() and then get its value status = digitalRead(2); in loop().
Arduino question on interrupts:
For my Arduino RTC project I need to put my Arduino to sleep until interrupted by either a pin interrupt or by a single char present on the serial port (an arbitrary character) -- How may I achieve this?
I see that a pin interrupt is relatively straightforward, but I'm unable complete this by the serial port [I could poll the serial port, but this wastes energy].
Suggestions welcome