Slow pin change interrups
Posted: Sat Oct 07, 2017 8:31 amHi,
I wanted to write an I2C sniffer and wanted to use pin change interrupts to monitor the changes of SCL/SDA.
The problem is, the code is way too slow for 400kHz I2C.
Here is my code:
And this is what I get on the scope, yellow connected to PIN_SCL and blue to PIN_SCL_O.
Where is the error? I cannot believe it is supposed to be so slow...
Thx
I wanted to write an I2C sniffer and wanted to use pin change interrupts to monitor the changes of SCL/SDA.
The problem is, the code is way too slow for 400kHz I2C.
Here is my code:
Code: Select all
#define PIN_SDA 5 // D1
#define PIN_SCL 4 // D2 -- yellow scope trace
#define PIN_SDA_O 0 // D3
#define PIN_SCL_O 2 // D4 -- blue scope trace
void setup()
{
pinMode(PIN_SDA_O, OUTPUT);
pinMode(PIN_SCL_O, OUTPUT);
pinMode(PIN_SDA, INPUT);
pinMode(PIN_SCL, INPUT);
attachInterrupt(PIN_SCL, chgSCL, CHANGE);
attachInterrupt(PIN_SDA, chgSDA, CHANGE);
}
void loop()
{
}
void chgSCL() {
uint8_t _sda = ((GPI >> PIN_SDA) & 1);
uint8_t _scl = ((GPI >> PIN_SCL) & 1);
if (_scl) {
GPOS = (1 << PIN_SCL_O);
}
else {
GPOC = (1 << PIN_SCL_O);
}
}
void chgSDA() {
uint8_t _sda = ((GPI >> PIN_SDA) & 1);
uint8_t _scl = ((GPI >> PIN_SCL) & 1);
if (_sda) {
GPOS = (1 << PIN_SDA_O);
}
else {
GPOC = (1 << PIN_SDA_O);
}
}
And this is what I get on the scope, yellow connected to PIN_SCL and blue to PIN_SCL_O.
Where is the error? I cannot believe it is supposed to be so slow...
Thx