Long delay in first call to interrupt

[plerup]

Hi,

I'm using the standard Arduino routines for setting up an interrupt for a GPIO pin

pinMode(RX_PIN, INPUT);
attachInterrupt(RX_PIN, rxInt, FALLING);

The problem I get is that the very first call to the interrupt routine (after system reset) has a delay of > 20 uS from the GPIO pin flank to the actual call. Any subsequent calls just have a delay of 4 uS.

If I use the SDK routines like this:

ETS_GPIO_INTR_ATTACH(intr, 0);
GPIO_REG_WRITE(GPIO_STATUS_W1TC_ADDRESS, BIT(RX_PIN));
gpio_pin_intr_state_set(GPIO_ID_PIN(RX_PIN), GPIO_PIN_INTR_NEGEDGE);

then I don't get this behavior.

Any ideas why this is so?

Thanks
/Peter

[Links2004]

try to change the
void interrupt_handler(void *arg) {
to
void ICACHE_RAM_ATTR interrupt_handler(void *arg) {
in
core_esp8266_wiring_digital.c

[igrr]

I think this method won't work because linker directives have higher
precedence over compiler attributes. We would have to move interrupt
handler (and other routines currently marked with ICACHE_RAM_ATTR) to a
separate .c file which will not be subject to the rule defined in linker
script.

We also need to move section renaming to a later stage, otherwise stuff
like -gc-sections doesn't work. Have to think about this a bit...

On Wed, Sep 16, 2015, 23:27 Markus notifications@github.com wrote:

try to change the
void interrupt_handler(void *arg) {
to
void ICACHE_RAM_ATTR interrupt_handler(void *arg) {
in
core_esp8266_wiring_digital.c

—
Reply to this email directly or view it on GitHub
#797 (comment).

[plerup]

Here is an example that can be used to show this phenomenon. Just shortcut pin 12 and 14

My result is like this:

Interrupt test started
Delay = 23
Delay = 5
Delay = 4
Delay = 4
Delay = 5
Delay = 4

#define OUT 12
#define IN 14
unsigned long intrTime = 0;
void intr () {
  intrTime = micros();
}
void setup() {
  Serial.begin(115200);
  pinMode(OUT, OUTPUT);
  digitalWrite(OUT, HIGH);
  pinMode(IN, INPUT);
  attachInterrupt(IN, intr, FALLING);
  Serial.println("Interrupt test started");
}
void loop() {
  unsigned long start = micros();
  digitalWrite(OUT, LOW);
  delay(1000);
  Serial.print("Delay = ");
  Serial.println(intrTime-start);
  digitalWrite(OUT, HIGH);
  delay(2000);
}

[igrr]

Thank you for the example, the reason why this happens is totally clear.
The question now is how to improve our linker rules to meet all of the
following:

• Place code into flash by default
• Allow -ffunction-sections and -fdata-sections to generate separate
  sections for each symbol so that -gc-sections will work
• Make it possible to mark functions to be placed into RAM.

As I see it, doing all three at the same time is tricky... Perhaps we need
to relax these criteria a bit, i.e. ignore garbage collection requirement
for functions placed into RAM.
Comments and ideas are totally welcome here.

P.S. of course there is a simple workaround for this particular case
(mentioned in my previous reply). But since this isn't a blocker, I would
prefer to fix this by solving the underlying issue, not it's manifestation.

On Thu, Sep 17, 2015, 20:56 Peter Lerup notifications@github.com wrote:

Here is an example that can be used to show this phenomenon. Just shortcut
pin 12 and 14

My result is like this:

Interrupt test started
Delay = 23
Delay = 5
Delay = 4
Delay = 4
Delay = 5
Delay = 4

#define OUT 12
#define IN 14
unsigned long intrTime = 0;
void intr () {
intrTime = micros();
}
void setup() {
Serial.begin(115200);
pinMode(OUT, OUTPUT);
digitalWrite(OUT, HIGH);
pinMode(IN, INPUT);
attachInterrupt(IN, intr, FALLING);
Serial.println("Interrupt test started");
}
void loop() {
unsigned long start = micros();
digitalWrite(OUT, LOW);
delay(1000);
Serial.print("Delay = ");
Serial.println(intrTime-start);
digitalWrite(OUT, HIGH);
delay(2000);
}

—
Reply to this email directly or view it on GitHub
#797 (comment).

[plerup]

I'm confident that you will come up with a good solution. Thank you so much for your fantastic work on this project!

The reason for my problem is that I'm implementing a SoftwareSerial class and got problem with the very first byte when running at 115200 baud due to this.

[alecapu]

Hi,
I've a very strange interrupt problem me too. I've a sample I2S application that use TX and RX I2S channels in loopback. If I compile the code with the ESP SDK every things work fine. If I try to migrate it to Arduino the DMA interrupt is not called.... some one with more experience can help me?

[me-no-dev]

@alecapu you have code for I2S-RX? Can you share that with us so we can add it to the core?