I2C not working on ESP32

[muktillc]

Hardware:

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

Description:

I am not able to generate the I2C clock. I have an ST microelectronics accelerator that I am using which has an I2C interface. So just wanted to see if I2C is working.

I have seen many people running into the same problem but could not find a solution for this issue. No errors generated when compiling the code.

Please find my code below.

Sketch:

//Change the code below by your sketch

#include "Wire.h"

void setup() {
Wire.begin(21,22);
Serial.begin(115200);
Wire.setClock(400000); // choose 400 kHz I2C rate
Serial.println("Start i2c-test");
}

void loop() {
byte error;

// 0x20 is the address of a pcf8574 GPIO expander
Serial.println("Try to contact 0x20");
uint8_t data = 0;
// Wire.beginTransmission(0x3A);
// error = Wire.endTransmission();
Wire.beginTransmission(0x3B); // Initialize the Tx buffer
Wire.write(0x0F); // Put WHO_AM_I address in Tx buffer
Wire.endTransmission(false); // Send the Tx buffer, but send a restart to keep connection alive
Wire.requestFrom(0x3B, 1); // Read two bytes from slave PROM address
while (Wire.available()) {
data = Wire.read(); } // Put read results in the Rx buffer
Serial.print("Error code is:");
Serial.println(data);

delay(1000);
}

[stickbreaker]

@muktillc , in issue #90 I commented a possible solution.
Here is a I2C scanner that works on ESP32's
The Debug output shows my problem. The first section of output is what happens when the SDA line is held low by the ESP32. I touched EN(reset) on my WeMos bluetooth&battery. The reset cleared the SDA line and the scan successfully worked on the second attempt.

My system:

5v segment

0x20,0x21 (MCP23008) I/O expanders connected to 4x4 matrix and 20x4 LCD
0x50 24LC32 EEPROM
0x68 DS1307 RTC

3.3v segment

0x51,0x55,0x56 24LC512
0x52,0x53,0x54 24LC64

Scanner Code

/* I2C slave Address Scanner
for 5V bus
 * Connect a 4.7k resistor between SDA and Vcc
 * Connect a 4.7k resistor between SCL and Vcc
for 3.3V bus
 * Connect a 2.4k resistor between SDA and Vcc
 * Connect a 2.4k resistor between SCL and Vcc

 */

#include <Wire.h>

void scan(){
Serial.println(" Scanning I2C Addresses");
uint8_t cnt=0;
for(uint8_t i=0;i<128;i++){
  Wire.beginTransmission(i);
  uint8_t ec=Wire.endTransmission(true);
  if(ec==0){
    if(i<16)Serial.print('0');
    Serial.print(i,HEX);
    cnt++;
  }
  else Serial.print("..");
  Serial.print(' ');
  if ((i&0x0f)==0x0f)Serial.println();
  }
Serial.print("Scan Completed, ");
Serial.print(cnt);
Serial.println(" I2C Devices found.");
}

bool i2cReady(uint8_t adr){
uint32_t timeout=millis();
bool ready=false;
while((millis()-timeout<100)&&(!ready)){
	Wire.beginTransmission(adr);
	ready=(Wire.endTransmission()==0);
	}
return ready;
}

void eepromSize(){
Serial.println("Discovering eeprom sizes 0x50..0x57");
uint8_t adr=0x50,i;
uint16_t size;
char buf[64];
while(adr<0x58){
	i=0;
	size = 0x1000; // Start at 4k
	i += sprintf_P(&buf[i],PSTR("0x%02X: "),adr);
	if(i2cReady(adr)) { // EEPROM answered
		uint8_t zeroByte;
		Wire.beginTransmission(adr);
		Wire.write((uint8_t)0); // set address ptr to 0, two bytes High
		Wire.write((uint8_t)0); // set address ptr to 0, two bytes Low
		uint8_t err=Wire.endTransmission();
		if(err==0){// worked
		  err=Wire.requestFrom(adr,(uint8_t)1);
			if(err==1){// got the value of the byte at address 0
				zeroByte=Wire.read();
				uint8_t saveByte,testByte;
				do{
					if(i2cReady(adr)){
						Wire.beginTransmission(adr);
						Wire.write(highByte(size)); // set next test address
						Wire.write(lowByte(size));
						Wire.endTransmission();
						err=Wire.requestFrom(adr,(uint8_t)1);
						if(err==1){
							saveByte=Wire.read();
							Wire.beginTransmission(adr);
							Wire.write(highByte(size)); // set next test address
							Wire.write(lowByte(size));
							Wire.write((uint8_t)~zeroByte); // change it
							err=Wire.endTransmission();
							if(err==0){ // changed it
								if(!i2cReady(adr)){
									i+=sprintf_P(&buf[i],PSTR(" notReady2.\n"));
									Serial.print(buf);
									adr++;
									break;
									}
								Wire.beginTransmission(adr);
								Wire.write((uint8_t)0); // address 0 byte High
								Wire.write((uint8_t)0); // address 0 byte Low
								err=Wire.endTransmission();
								if(err==0){
									err=Wire.requestFrom(adr,(uint8_t)1);
									if(err==1){ // now compare it
									  testByte=Wire.read();
										}
									else {
										testByte=~zeroByte; // error out
										}
									}
								else {
									testByte=~zeroByte;
									}
								}
							else {
								testByte = ~zeroByte;
								}
							//restore byte
							if(!i2cReady(adr)){
								i+=sprintf_P(&buf[i],PSTR(" notReady4.\n"));
								Serial.print(buf);
								adr++;
								break;
								}
							
							Wire.beginTransmission(adr);
							Wire.write(highByte(size)); // set next test address
							Wire.write(lowByte(size));
							Wire.write((uint8_t)saveByte); // restore it
							Wire.endTransmission();
							}
						else testByte=~zeroByte;
						}
					else testByte=~zeroByte;
					if(testByte==zeroByte){
						size = size <<1;
						}
					}while((testByte==zeroByte)&&(size>0));
				if(size==0) i += sprintf_P(&buf[i],PSTR("64k Bytes"));
				else i+=sprintf_P(&buf[i],PSTR("%dk Bytes"),size/1024);
				if(!i2cReady(adr)){
					i+=sprintf_P(&buf[i],PSTR(" notReady3.\n"));
					Serial.print(buf);
					adr++;
					continue;
					}
				Wire.beginTransmission(adr);
				Wire.write((uint8_t)0); // set address ptr to 0, two bytes High
				Wire.write((uint8_t)0); // set address ptr to 0, two bytes Low
				Wire.write(zeroByte);  //Restore
				err=Wire.endTransmission();
				}
			else i+=sprintf_P(&buf[i],PSTR("Read 0 Failure"));
			}
		else i+=sprintf_P(&buf[i],PSTR("Write Adr 0 Failure"));
			
	  }
	else i+=sprintf_P(&buf[i],PSTR("Not Present."));
	Serial.println(buf);
	adr++;
	}
}

void setup(){
Serial.begin(115200);
Wire.begin();
scan();
Serial.println();
eepromSize();
}

void loop(){}

Debug Output

 Scanning I2C Addresses
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 
Scan Completed, 0 I2C Devices found.

Discovering eeprom sizes 0x50..0x57
0x50: Not Present.
0x51: Not Present.
0x52: Not Present.
0x53: Not Present.
0x54: Not Present.
0x55: Not Present.
0x56: Not Present.
0x57: Not Present.
ets Jun  8 2016 00:22:57

rst:0x1 (POWERON_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0010,len:4
load:0x3fff0014,len:572
load:0x40078000,len:0
load:0x40078000,len:9880
entry 0x400789d8
 Scanning I2C Addresses
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 
20 21 .. .. .. .. .. .. .. .. .. .. .. .. .. .. 
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 
50 51 52 53 54 55 56 .. .. .. .. .. .. .. .. .. 
.. .. .. .. .. .. .. .. 68 .. .. .. .. .. .. .. 
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 
Scan Completed, 10 I2C Devices found.

Discovering eeprom sizes 0x50..0x57
0x50: 4k Bytes
0x51: 64k Bytes
0x52: 8k Bytes
0x53: 8k Bytes
0x54: 8k Bytes
0x55: 64k Bytes
0x56: 64k Bytes
0x57: Not Present.

Chuck.

[EBZ-Krisemendt]

hello @muktillc
any particullar reason your not using designated wire ports (22/23) or is it just a typo in your code?

[muktillc]

I thought the designated ports are pins 21 and 22. Are they 22 and 23??

…

On Oct 18, 2017 6:58 AM, "EBZ-Krisemendt" ***@***.***> wrote: hello @muktillc <https://github.com/muktillc> any particullar reason your not using designated wire ports (22/23) or is it just a typo in your code? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#741 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/Aetc8NKnzoqcb76-H5OEGBDso5P7oPmrks5stdnSgaJpZM4P854w> .

[EBZ-Krisemendt]

shame on me, it's 22/23 on adafruit huzzah32. it's indeed 21/22 on official dev-board, sorry

[muktillc]

one quick question regarding the SPI. I am trying to get the SPI work and my sensor is responding but for some reason the MISO pin (pin #19) is not accepting any input. I tested the output of the sensor and it gives the expected output for the WHO_AM_I register but as soon as I connect the SDO of the sensor to MISO, the output goes down to zero and I don't see anything oscilloscope. Wondering if you have seen anything like this.

…

On Wed, Oct 18, 2017 at 7:07 AM, EBZ-Krisemendt ***@***.***> wrote: shame on me, it's 22/23 on adafruit huzzah32. it's indeed 21/22 on official dev-board, sorry — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#741 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/Aetc8F32vTnT-El7hVBV2kiPItKpFq3bks5stdvcgaJpZM4P854w> .

[me-no-dev]

pin 19 is working fine here :) bad soldering? something else pulling the pin?

[muktillc]

Sorry for the late reply. I was able to get this part working and the SPI works as desired. I had to change the pin 19 to pin 22 for my code and it seems to be working. However, I ran into another issue, which was my original problem. I have a AT30TS75 temperature sensor which only has I2C. I could not get I2C working on pin 21 and 22 using Arduino IDE, which I believe are the default pins. I was wondering if there is a way to change the pins from 21 and 22 to 32 and 33. How do i do it?

[stickbreaker]

@muktillc
I think I found and issue with the ReStart operation. In your Example:

/ 0x20 is the address of a pcf8574 GPIO expander
Serial.println("Try to contact 0x20");
uint8_t data = 0;
// Wire.beginTransmission(0x3A);
// error = Wire.endTransmission();
Wire.beginTransmission(0x3B); // Initialize the Tx buffer
Wire.write(0x0F); // Put WHO_AM_I address in Tx buffer
Wire.endTransmission(false); // Send the Tx buffer, but send a restart to keep connection alive
Wire.requestFrom(0x3B, 1); // Read two bytes from slave PROM address
while (Wire.available()) {
data = Wire.read(); } // Put read results in the Rx buffer
Serial.print("Error code is:");
Serial.println(data);
delay(1000);
}

Is that Restart( Wire.endTransmission(false);) necessary for the correct operation of your sensor?
If your sensor requires the restart, I think we'll have to make a new function in Wire() because I think the hardware cannot hang the bus waiting after the sendStop=false;. An I2C bus timeOut will occur.

If you want to test my theory out I'll write a function that you can insert into your ESP source files
Arduino\hardware\espressif\esp32\cores\esp32\esp32-hal-i2c.c
Arduino\hardware\espressif\esp32\cores\esp32\esp32-hal-i2c.h
Arduino\hardware\espressif\esp32\libraries\Wire\src\Wire.cpp
Arduino\hardware\espressif\esp32\libraries\Wire\src\Wire.h

uint8_t Wire.transact(const uint8_t ID,uint8_t* writeBytes,const uint8_t writeLen, const uint8_t readLen);

to use it with your example:

uint8_t writeBuf[10];
uint8_t writeLen=0;
writeBuf[writeLen++] = 0x0f; //build command buffer

uint8_t err=Wire.transact(0x3B,writeBuf,writeLen,1);
if(err!=1){ // bogus, Bad stuff
  Serial.print("error during transact");
  }
else{
  while (Wire.available()) {
    Serial.printf("%d ",Wire.read();
    }

Chuck.

[stickbreaker]

@muktillc check out my message #839 . It may be a solution for your problems.

Chuck.

[zachfi]

I believe I'm seeing this also, through the https://github.com/adafruit/Adafruit_BME280_Library library which uses Wire under the hood. I just purchased some dev modules hoping to use I2c, but can't get anything function. Hoping this all gets straitened out soon, so thanks for working on it.

[njbuch]

I am seeing this as well. Tryed several weird pin-defs - with no luck. Still not sure which is the official I2C pins on my "LOLIN32 Lite" board.

My last attempt, not working, was the following (only snippet).

#define I2C_SDA_PIN 23
#define I2C_SCL_PIN 22

void setup()
{
  Serial.begin(115200);                                            
  Wire.begin( I2C_SDA_PIN, I2C_SCL_PIN, 1000000 );

[stickbreaker]

@njbuch try one of my branches, either Main or Wire-Destructor. My latest Releaset V0.2.0 has a zip file that contains only the required files. These required files are just copied over the files from this repo.

Also, you are specifying the i2c Bus to operate at 1MHz?

I2C has two recognized speeds 100KHz and 400KHz. As the speed increases the Pullup resistor values need to decrease. Check out my Wiki page on resistor value considerations: Pullup Considerations At 1MHz I doubt you have low enough values of resistors for the bus to return to HIGH between bits, also if you do have low enough value, you are approaching the limits of the output drivers.

Chuck.