Using 2nd buses for I2C AND USART (I2C2 AND USART2)

[AakankshaS-ITSPE]

Dear team,
I am attempting to use an rtc module in I2C2 on PB10 and PB11 pins.
While my firmware work well with arduino, I suspect it might either be a pull up issue or a library issue.
After adding pull up resistors, and running i2c address scanner, the addresses are not detected until and unless i call the address. even when it is detected, there are ghiist addresses as well.
i tried changing the library file for the pull ups , pulldowns and no pull, issue persists

Kindly help please.
Similarly i am tryint to use usart 2 for serial debugging same issue

[fpistm]

Could you tell which board you used? Options? Version of the core? Sketch used? Schematics of your setup....

[fpistm]

That is normal you invert pin signal for the constructor, it is:
TwoWire Wire2(PB11, PB10);

It is explicitly wrote in the I2C scanner example:

Arduino_Core_STM32/libraries/Wire/examples/i2c_scanner/i2c_scanner.ino

Lines 47 to 49 in f1432b0

	If you want to use the two I2Cs simultaneously, create a new instance for the second I2C
	TwoWire Wire2(PB11,PB10);
	Wire2.begin();

Here I2C scanner log then your sketch with the proper instantiation:

[AakankshaS-ITSPE]

Thank you for your input, I did that, however, I2C address scanner does not detect the address at 0x68 and 0x50.
I am using DS3231 RTC module with EEPROM
BUT, if i call the addresses they get detected.

#include <Wire.h>
// Use I2C2 (PB10 = SCL, PB11 = SDA)
TwoWire Wire2(PB11, PB10);
#define EEPROM_ADDR 0x57 // AT24C02
#define RTC_ADDR  0x68 // DS3231
bool probeDevice(TwoWire &w, uint8_t addr) {
 w.beginTransmission(addr);
 return (w.endTransmission() == 0);
}

void setup() {
 Serial.begin(9600);
 delay(50); // let devices power up
 Serial.println(" I2C2 (PB10=SCL, PB11=SDA) startup");
 Wire2.begin();
}

void loop() {
 Serial.println("---- I2C2 Check ----");
 // RTC check
 if (probeDevice(Wire2, RTC_ADDR)) {
  Serial.println(" RTC detected at 0x68");
 } else {
  Serial.println(" RTC not responding at 0x68");
 }
 // EEPROM check
 if (probeDevice(Wire2, EEPROM_ADDR)) {
  Serial.println(" EEPROM detected at 0x57");
 } else {
  Serial.println(" EEPROM not responding at 0x57");
 }
 Serial.println("--------------------\n");
 delay(3000);
}

Why is my device not detecting in the I2C scanner example? What might be the reason...all addresses show "unknown error at address.. " If i extend my code to an application of the RTC module, example, a timestamp code, the I2C bus seems incomplete, as the code hangs

[fpistm]

Are you sure you have a legacy STM32F103C8 ?

[fpistm]

I have a DS1307 from Adafruit:
https://www.adafruit.com/product/3296
I2C scanner properly detects it using PB10/PB11 and runs fine using Adafruit RTC lib:
https://github.com/adafruit/RTClib

So don't know what can be your issue.

• Not a legacy STM32F103C8
• Wiring issue
• hardware issue

[AakankshaS-ITSPE]

Apologies for the late reply.

1. not a legacy STM32F103C8 (can be an issue, but the bluepill is from a verified vendor, and i have used it for various other projects)
2. wiring issue (I don't think so; I rechecked multiple times)
3. Hardware issue (The RTC module is working well with the Arduino Uno, and so is the library.)

The issue lies with the I2C bus scan; it updates when I call the address but doesn't stay connected for long. Due to my time-sensitive project, I will now use the library and STM32 Arduino framework and run I2C through bare-metal programming.
Thank you so much for the help. In the meantime, I'll test USART2.
Thank you so much for the prompt and effective responses. Have a great day!