Description
This is probably related to #5875
I'm using Wire.requestFrom(address, 1); also to scan the I2C bus. If it returns 1, a device is present, otherwise not. For some reason, the current version (both the official 2.0.1 release as well as the latest master including the fix from #5910) take very long in case of an error. Consider this example program (slightly modified from the default WireScan example):
#include "Wire.h"
void setup() {
Serial.begin(115200);
Wire.begin();
Serial.printf("Wire timeout: %dms", Wire.getTimeOut());
}
void loop() {
byte error = 0;
byte address = 0;
int nDevices = 0;
delay(5000);
Serial.println("Scanning for I2C devices ...");
for(address = 0x01; address < 0x7f; address++){
// Wire.beginTransmission(address);
// error = Wire.endTransmission();
error = Wire.requestFrom(address, (byte)1) == 1 ? 0 : 2;
if (error == 0){
Serial.printf("I2C device found at address 0x%02X\n", address);
nDevices++;
} else if(error != 2){
Serial.printf("Error %d at address 0x%02X\n", error, address);
}
else
{
Serial.printf("No device found at address 0x%02X\n", address);
}
}
if (nDevices == 0){
Serial.println("No I2C devices found");
}
}With the default implementation (using the two commented lines above) the scan is fast and one loop takes around 2 seconds. The above code, however, takes about 1 second for each address it scans (except for the addresses where a device is present). The timeout for the I2C bus is set to the default of 50ms.
Expected Behavior
Wire.readFrom(address, 1); takes 50ms in case there's no device at the given address.
Actual Behavior
It takes about 1 second.
Hardware:
Board: ESP32 Dev Module
Core Installation version: Tested 2.0.1 and 399f4ec. The problem did not occur with 1.0.6
IDE name: Arduino IDE
Flash Frequency: 80Mhz
PSRAM enabled: no
Upload Speed: 921600
Computer OS: Windows 10