how to use Serial event in esp32 arduino ide

[jt040-jetnet]

Hardware:

Board: ESP32 Dev Module
Core Installation/update date: 11/jul/2017
IDE name: Arduino IDE
Flash Frequency: 40Mhz
Upload Speed: 115200

Description:

Hello all
i want to receive some data serially on my esp32
for that i want to enable uart receive interrupt ,
in arduino serialEvent() is used for receive interrupt ,but its not working for esp32
below is code available in examples of arduino ide
can any one suggest me how to receive data in interrupt for esp32 Arduino IDE

Sketch:

String inputString = ""; // a String to hold incoming data
boolean stringComplete = false; // whether the string is complete

void setup() {
// initialize serial:
Serial.begin(9600);
// reserve 200 bytes for the inputString:
inputString.reserve(200);
}

void loop() {
// print the string when a newline arrives:
if (stringComplete) {
Serial.println(inputString);
// clear the string:
inputString = "";
stringComplete = false;
}
}

/*
SerialEvent occurs whenever a new data comes in the hardware serial RX. This
routine is run between each time loop() runs, so using delay inside loop can
delay response. Multiple bytes of data may be available.
*/
void serialEvent() {
while (Serial.available()) {
char inChar = (char)Serial.read();
inputString += inChar;
if (inChar == '\n') {
stringComplete = true;
}
}
}

[shaielc]

hi haven't seen an implementation of the serial event anywhere ,so i kinda added it for my project no clue if it is stable (just made it), but it works for me at the moment. This is a "bandage" solution I didn't go deep into the idf to find out how it should have been done.

https://gist.github.com/shaielc/28a94b39dbd232974a6d78e384d44b0f

[rappleto]

Thanks very much, @shaielc.
To apply this the hard way, I took the four source files from the zip, and manually applied the changes that you had made to the same files in my ~arduino-1.8.5/hardware/espressif/esp32/cores/esp32 folder.
I ended up using the highly intuitive vimdiff for the compares.
I learned about IRAM_ATTR for interrupt routines - important safety tip, thank-you.
In this case, the interrupt routine assignment from your serialEventExample.ino is set explicitly. If I understand correctly, this is a true interrupt routine as opposed to the Arduino target implicit calls to serialEvent() which just happen after every loop() cycle.

[shaielc]

This just adds your interrupt function after the handling of the original uart interrupt from the idf.
glad to help!

[Vorms]

Hello, many thanks for this article.
I would like to know if it is possible to declare the input buffer "inputString" in a class or not.
My goal is to "share" the input string with a class. I have to examine the string in a class.
Any example will be welcome !
Best regards
Thierry

[IngYordiDelgado]

i am having problems using this and spi comunication, SPI doesnt'work i have a digital potentiometer and i tested with other program but when i use serialevent in the sketch it doesn't work. is there any way to solve this ?, i'm using a heltek wifi kit

[rappleto]

From what I gather, SPI uses a different driver from this UART serialevent one. There is some documentation here, though I didn't see much that explains how to register and use the SPI interrupt routine:
https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/peripherals/spi_master.html
and further, the use of interrupt driven SPI seems a bit bizarre in that instead of handling the interrupt, the docs suggest you poll spi_device_get_trans_result() to see if the interrupt driven transactions are complete.
The API reference shows int spicommon_irqsource_for_host(spi_host_device_t host) which might allow you to tap into the IRQ instead of polling the result from the driver.

[rappleto]

As a starting point you could try running this:
https://github.com/espressif/esp-idf/blob/master/examples/peripherals/spi_master/main/spi_master_example_main.c

[shaielc]

@IngYordiDelgado
If you are using spi in master mode you won't have an event, since communication is controlled by the master via pulling the SS line down.
If you are using it in slave mode you could raise an interrupt when the SS input is pulled down, if this is the case I have a gist that implements the spi slave for esp32 , if it wasn't already implemented.

[rappleto]

Hello, many thanks for this article.
I would like to know if it is possible to declare the input buffer "inputString" in a class or not.
My goal is to "share" the input string with a class. I have to examine the string in a class.
Any example will be welcome !
Best regards
Thierry

You can declare it in a class, but as a static member. But I don't see why you would need to examine it in a class, or if you do want to you can certainly access an unclassed variable from within a class. This was tried out on an ATmega328p using the Arduino IDE.

It shows a global inputString accessed by an object/instance method: parseInput(), and by a static class method: printStrings() as well as by a non-class method: setup().
For kicks I also added this. The static class String classyStaticString is also accessed by those same three methods.

String inputString = "";

class cInputParser
{
public:
void parseInput();
static String classyStaticString;
};

// Note: without this the classyStaticString will not be found by the linker
String cInputParser::classyStaticString;

class cStringPrinter
{
public:
static void printStrings();
};

cInputParser ip;

void cInputParser::parseInput()
{
char first = inputString.charAt(0);

classyStaticString = inputString;

switch (first)
{
case 'a':
inputString = "b";
break;
case 'b':
inputString = "c";
break;
default:
inputString = "a";
break;
}
}

void cStringPrinter::printStrings()
{
Serial.print("classyStaticString=");
Serial.print(cInputParser::classyStaticString);
Serial.print(" inputString=");
Serial.println(inputString);
}

void setup()
{
// put your setup code here, to run once:
Serial.begin(115200);
cInputParser::classyStaticString = "something";
inputString = "b";
cStringPrinter::printStrings();
}

void loop()
{
// put your main code here, to run repeatedly:
ip.parseInput();
cStringPrinter::printStrings();
delay(1000);
}

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This stale issue has been automatically closed. Thank you for your contributions.

[yottayuan]

hi haven't seen an implementation of the serial event anywhere ,so i kinda added it for my project no clue if it is stable (just made it), but it works for me at the moment. This is a "bandage" solution I didn't go deep into the idf to find out how it should have been done.

https://gist.github.com/shaielc/28a94b39dbd232974a6d78e384d44b0f

could u share the code?

[yottayuan]

hi haven't seen an implementation of the serial event anywhere ,so i kinda added it for my project no clue if it is stable (just made it), but it works for me at the moment. This is a "bandage" solution I didn't go deep into the idf to find out how it should have been done.

https://gist.github.com/shaielc/28a94b39dbd232974a6d78e384d44b0f

hi, could u share the code? the link cannot be getted to .