Please help me getting I2C Slave to work on STM32F103

pilot · December 1, 2024, 7:51am

In short:
Arduino Wire library fails to act as a Slave on at least STM32F103Cx , :

github.com/arduino/ArduinoCore-API

Bug in I2C slave STM32F103

opened 04:43PM - 30 Nov 24 UTC

closed 10:21PM - 30 Nov 24 UTC

AndKe

bug invalid

### Description ``` #include <Wire.h> long lastms; volatile int x = 0; volatile… int y = 0; #define STM void receiveEvent(int howMany) { x = Wire.read(); } void requestEvent() { y = 1; } void setup() { Serial.begin(115200); #ifdef STM //STM32F103 pinMode(PB6, INPUT); //PB6=SCL pinMode(PB7, INPUT); //PB7=SDA Wire.setSCL(PB6); Wire.setSDA(PB7); #elif //Arduino Nano pinMode(A4, INPUT); pinMode(A5, INPUT); //Wire.setSDA(A4); //Wire.setSCL(A5); #endif Wire.begin(11); // join i2c bus as slave //Wire.onRequest(requestEvent); Wire.onReceive(receiveEvent); lastms = millis(); } void loop() { if (millis() > lastms + 1000) { Serial.print("-"); lastms = millis(); } if (x != 0) { Serial.print("U:0x"); Serial.println(x, HEX); x = 0; } if (y != 0) { Serial.println("V"); y = 0; } } ``` ### Environment - Boards platform name: Bluepill / own board / Arduino Nano (Nano and Leonardo works fine) - Boards platform version (as shown in Boards Manager): ![Image](https://github.com/user-attachments/assets/d20b4dab-570f-472c-a762-15f614f586d5) - ArduinoCore-API version (if you manually installed it): ### Current behavior If compiled for Nano, the application works. (displaying the incoming I2C requests.) When compiled for STM32F103 - with CDC serial, it does not. (it outputs only the "-" each 1sec.) The incoming data is at the same time decoded by an oscilloscope, so pullups etc are ok. ### Expected behavior I expect the code to work on STM32F103C8 /Bluepill like it did on Nano ### Additional information When on Bluepill, On incoming I2C data, PB6 (SCK) is being pulled low, and held low by the controller, effectively killing all further traffic. This happens even if USB /Serial support is set to NONE

I also tried to ask Copilot for help, but that did not result in working code.

What I need is to recieve and respond to Write requests - much like the test app
issue at Arduino poster above.

I also tried the super-bloated STM32CubeMX, but that generated many files, and much code, including irrelevant code that was #ifdef’ed for other MCU series that I selected, with no clear way to use it.

Please point me to some source that I can use as example on how to recieve/respond to I2C slave requests. Something like the “wire” library from Arduino, or just code for IC2C1 /PB6/PB7

sivar2311 · December 1, 2024, 7:58am

Duplicate of STM32F108 as Slave won't work
Duplicate of STM32F103 as I2C slave the PlatformIO way? (non-Arduino?)

Please ask questions just once.

pilot · December 1, 2024, 8:05am

Requested for deletion of those.
Those look like the same for you, but those are in very different phases of the the troubleshooting, in the beginning I had no clue why this happened, now I need help on how to workaround it.