On the Uno I had them connected like
SDA via Uno SDA -> ESP32 GPIO21
SCL via Uno SCL -> ESP32 GPIO22
I also tried flipping them like this:
SDA via Uno SDA -> ESP32 GPIO22
SCL via Uno SCL -> ESP32 GPIO21
Connections are as follows:
SDA via ESP32 GPIO21 -> ESP8266 GPIO4
SCL via ESP32 GPIO22 -> ESP8266 GPIO5
I also tried flipping them, as follows:
SDA via ESP32 GPIO21 -> ESP8266 GPIO5
SCL via ESP32 GPIO22 -> ESP8266 GPIO4
I have present a 4.7kOhm pull-up resistor from SDA&SCL to +3.3V
All these combinations led to nil result on I2C bus scanners. I tried 5 scanners and 3 Wire libs. Here is output from one of the more comprehensive scanners:
Code: Select all
21:58:06.078 -> I2C Scanner to scan for devices on each port pair D0 to D7
21:58:06.078 -> Scanning (SDA : SCL) - GPIO4 : GPIO5 - No I2C devices found
21:58:06.112 -> Scanning (SDA : SCL) - GPIO4 : GPIO21 - No I2C devices found
21:58:06.180 -> Scanning (SDA : SCL) - GPIO4 : GPIO22 - No I2C devices found
21:58:06.249 -> Scanning (SDA : SCL) - GPIO4 : GPIO2 - No I2C devices found
21:58:06.385 -> Scanning (SDA : SCL) - GPIO4 : GPIO14 - No I2C devices found
21:58:06.520 -> Scanning (SDA : SCL) - GPIO4 : GPIO12 - No I2C devices found
21:58:06.724 -> Scanning (SDA : SCL) - GPIO4 : GPIO13 - No I2C devices found
21:58:06.928 -> - No I2C devices found
21:58:07.165 -> Scanning (SDA : SCL) - GPIO5 : GPIO4 - No I2C devices found
21:58:07.437 -> Scanning (SDA : SCL) - GPIO5 : GPIO21 - No I2C devices found
21:58:07.743 -> Scanning (SDA : SCL) - GPIO5 : GPIO22 - No I2C devices found
21:58:08.050 -> Scanning (SDA : SCL) - GPIO5 : GPIO2 - No I2C devices found
21:58:08.418 -> Scanning (SDA : SCL) - GPIO5 : GPIO14 - No I2C devices found
21:58:08.822 -> Scanning (SDA : SCL) - GPIO5 : GPIO12 - No I2C devices found
21:58:09.230 -> Scanning (SDA : SCL) - GPIO5 : GPIO13 - No I2C devices found
21:58:09.670 -> - No I2C devices found
21:58:10.143 -> Scanning (SDA : SCL) - GPIO21 : GPIO4 - No I2C devices found
21:58:10.654 -> Scanning (SDA : SCL) - GPIO21 : GPIO5 - No I2C devices found
21:58:11.193 -> Scanning (SDA : SCL) - GPIO21 : GPIO22 - No I2C devices found
21:58:14.312 -> Scanning (SDA : SCL) - GPIO21 : GPIO2 - No I2C devices found
21:58:14.888 -> Scanning (SDA : SCL) - GPIO21 : GPIO14 - No I2C devices found
21:58:15.530 -> Scanning (SDA : SCL) - GPIO21 : GPIO12 - No I2C devices found
21:58:16.174 -> Scanning (SDA : SCL) - GPIO21 : GPIO13 - No I2C devices found
21:58:16.850 -> - No I2C devices found
21:58:17.555 -> Scanning (SDA : SCL) - GPIO22 : GPIO4 - No I2C devices found
21:58:18.292 -> Scanning (SDA : SCL) - GPIO22 : GPIO5 - No I2C devices found
21:58:19.071 -> Scanning (SDA : SCL) - GPIO22 : GPIO21 - Unknow error at address 0x09
21:58:19.139 -> Unknow error at address 0x0B
21:58:19.173 -> Unknow error at address 0x0F
21:58:19.173 -> Unknow error at address 0x12
21:58:19.173 -> Unknow error at address 0x13
21:58:19.207 -> Unknow error at address 0x15
21:58:19.207 -> Unknow error at address 0x16
21:58:19.207 -> Unknow error at address 0x17
21:58:19.241 -> Unknow error at address 0x19
21:58:19.241 -> Unknow error at address 0x1C
21:58:19.241 -> Unknow error at address 0x1D
21:58:19.241 -> Unknow error at address 0x1E
21:58:19.275 -> Unknow error at address 0x1F
21:58:19.275 -> Unknow error at address 0x23
21:58:19.309 -> Unknow error at address 0x25
21:58:19.309 -> Unknow error at address 0x26
21:58:19.309 -> Unknow error at address 0x27
21:58:19.309 -> Unknow error at address 0x29
21:58:19.342 -> Unknow error at address 0x2B
21:58:19.342 -> Unknow error at address 0x2F
21:58:19.376 -> Unknow error at address 0x31
21:58:19.376 -> Unknow error at address 0x32
21:58:19.376 -> Unknow error at address 0x33
21:58:19.376 -> Unknow error at address 0x34
21:58:19.376 -> Unknow error at address 0x35
21:58:19.410 -> Unknow error at address 0x36
21:58:19.410 -> Unknow error at address 0x37
21:58:19.410 -> Unknow error at address 0x38
21:58:19.410 -> Unknow error at address 0x39
21:58:19.410 -> Unknow error at address 0x3A
21:58:19.410 -> Unknow error at address 0x3B
21:58:19.444 -> Unknow error at address 0x3D
21:58:19.444 -> Unknow error at address 0x3E
21:58:19.444 -> Unknow error at address 0x3F
21:58:19.444 -> Unknow error at address 0x41
21:58:19.478 -> Unknow error at address 0x45
21:58:19.478 -> Unknow error at address 0x46
21:58:19.512 -> Unknow error at address 0x48
21:58:19.512 -> Unknow error at address 0x4C
21:58:19.546 -> Unknow error at address 0x4D
21:58:19.546 -> Unknow error at address 0x4F
21:58:19.580 -> Unknow error at address 0x54
21:58:19.580 -> Unknow error at address 0x55
21:58:19.580 -> Unknow error at address 0x56
21:58:19.580 -> Unknow error at address 0x57
21:58:19.614 -> Unknow error at address 0x5A
21:58:19.614 -> Unknow error at address 0x5B
21:58:19.648 -> Unknow error at address 0x5F
21:58:19.682 -> Unknow error at address 0x63
21:58:19.682 -> Unknow error at address 0x65
21:58:19.682 -> Unknow error at address 0x66
21:58:19.682 -> Unknow error at address 0x67
21:58:19.682 -> Unknow error at address 0x68
21:58:19.716 -> Unknow error at address 0x69
21:58:19.716 -> Unknow error at address 0x6A
21:58:19.716 -> Unknow error at address 0x6B
21:58:19.716 -> Unknow error at address 0x6C
21:58:19.716 -> Unknow error at address 0x6E
21:58:19.750 -> Unknow error at address 0x70
21:58:19.750 -> Unknow error at address 0x73
21:58:19.783 -> Unknow error at address 0x74
21:58:19.783 -> Unknow error at address 0x75
21:58:19.783 -> Unknow error at address 0x76
21:58:19.783 -> Unknow error at address 0x77
21:58:19.783 -> Unknow error at address 0x78
21:58:19.783 -> Unknow error at address 0x79
21:58:19.817 -> Unknow error at address 0x7B
21:58:19.817 -> Unknow error at address 0x7C
21:58:19.817 -> Unknow error at address 0x7D
21:58:19.817 -> No I2C devices found
21:58:19.817 -> Scanning (SDA : SCL) - GPIO22 : GPIO2 - No I2C devices found
21:58:20.662 -> Scanning (SDA : SCL) - GPIO22 : GPIO14 - No I2C devices found
21:58:21.507 -> Scanning (SDA : SCL) - GPIO22 : GPIO12 - No I2C devices found
21:58:22.391 -> Scanning (SDA : SCL) - GPIO22 : GPIO13 - No I2C devices found
21:58:23.342 -> - No I2C devices found
21:58:24.258 -> Scanning (SDA : SCL) - GPIO2 : GPIO4 - No I2C devices found
21:58:25.241 -> Scanning (SDA : SCL) - GPIO2 : GPIO5 - No I2C devices found
21:58:26.258 -> Scanning (SDA : SCL) - GPIO2 : GPIO21 - No I2C devices found
21:58:27.310 -> Scanning (SDA : SCL) - GPIO2 : GPIO22 - No I2C devices found
21:58:28.360 -> Scanning (SDA : SCL) - GPIO2 : GPIO14 - No I2C devices found
21:58:29.447 -> Scanning (SDA : SCL) - GPIO2 : GPIO12 - No I2C devices found
21:58:30.569 -> Scanning (SDA : SCL) - GPIO2 : GPIO13 - No I2C devices found
21:58:31.722 -> - No I2C devices found
21:58:32.911 -> Scanning (SDA : SCL) - GPIO14 : GPIO4 - No I2C devices found
21:58:34.133 -> Scanning (SDA : SCL) - GPIO14 : GPIO5 - No I2C devices found
21:58:35.360 -> Scanning (SDA : SCL) - GPIO14 : GPIO21 - No I2C devices found
21:58:36.649 -> Scanning (SDA : SCL) - GPIO14 : GPIO22 - No I2C devices found
21:58:37.933 -> Scanning (SDA : SCL) - GPIO14 : GPIO2 - No I2C devices found
21:58:39.254 -> Scanning (SDA : SCL) - GPIO14 : GPIO12 - No I2C devices found
21:58:39.491 -> Scanning (SDA : SCL) - GPIO14 : GPIO13 - No I2C devices found
21:58:39.491 -> - No I2C devices found
21:58:39.491 -> Scanning (SDA : SCL) - GPIO12 : GPIO4 - No I2C devices found
21:58:39.491 -> Scanning (SDA : SCL) - GPIO12 : GPIO5 - No I2C devices found
21:58:39.491 -> Scanning (SDA : SCL) - GPIO12 : GPIO21 - No I2C devices found
21:58:39.491 -> Scanning (SDA : SCL) - GPIO12 : GPIO22 - No I2C devices found
21:58:39.491 -> Scanning (SDA : SCL) - GPIO12 : GPIO2 - No I2C devices found
21:58:39.525 -> Scanning (SDA : SCL) - GPIO12 : GPIO14 - No I2C devices found
21:58:39.525 -> Scanning (SDA : SCL) - GPIO12 : GPIO13 - No I2C devices found
21:58:39.525 -> - No I2C devices found
21:58:39.525 -> Scanning (SDA : SCL) - GPIO13 : GPIO4 - No I2C devices found
21:58:39.525 -> Scanning (SDA : SCL) - GPIO13 : GPIO5 - No I2C devices found
21:58:39.525 -> Scanning (SDA : SCL) - GPIO13 : GPIO21 - No I2C devices found
21:58:39.525 -> Scanning (SDA : SCL) - GPIO13 : GPIO22 - No I2C devices found
21:58:39.559 -> Scanning (SDA : SCL) - GPIO13 : GPIO2 - No I2C devices found
21:58:39.559 -> Scanning (SDA : SCL) - GPIO13 : GPIO14 - No I2C devices found
21:58:39.559 -> Scanning (SDA : SCL) - GPIO13 : GPIO12 - No I2C devices found