serasidis/arduino_opencm3

arduino_opencm3's Issues

USART gibberish

The USART always sent gibberish even after trying many baudrates and parities.

I adapted the boards.txt and platform.txt to allow using a USB to serial adapter while waiting for a new ST-Link. The adapter uses the CP210x type chip and worked fine to upload the opencm3 bin to the generic STM32f103c board using the stm32flash program. The STM32 embedded bootloader requires 8e1 mode to send the bin to flash. My system is linux64 with kernel 4.10 and arduino 1.8.0.

I modified the ~/Arduino/hardware/arduino_opencm3/stm32/cores/opencm3/Uart.cpp to fix the problem.

Old:
    usart_set_baudrate(usart, baudrate);
    //usart_set_databits(usart, bits);
    //usart_set_stopbits(usart, stopbits);
    //usart_set_parity(usart, parity);
    usart_set_flow_control(usart, USART_FLOWCONTROL_NONE);
    usart_set_mode(usart, USART_MODE_TX_RX);
    rxBuffer.clear();
    txBuffer.clear();
    txRunning=false;
    usart_enable_rx_interrupt(usart);
    usart_enable(usart);

New:
    usart_set_baudrate(usart, baudrate);
    usart_set_databits(usart, HARDSER_DATA_8);    /* fixed */
    usart_set_stopbits(usart, USART_STOPBITS_1);  /* fixed */
    usart_set_parity(usart, USART_PARITY_EVEN);   /* fixed */
    usart_set_flow_control(usart, USART_FLOWCONTROL_NONE);
    usart_set_mode(usart, USART_MODE_TX_RX);
    rxBuffer.clear();
    txBuffer.clear();
    txRunning=false;
    usart_enable_rx_interrupt(usart);
    usart_enable(usart);

The USART databits, stopbits and parity settings were commented out in the original code. That might have left the USART unconfigured and causing the gibberish to be sent. Just adding these values suddenly allowed the USART to communicate correctly. I don't know why the code was at some point commented out and if that might affect anything else like USB for example. I also doubt my fix is the best technique to solve the problem.

The arduino examples now mostly work in my setup (except for the two opencm3 versions). The adc-test.cpp even works directly as adc-test.cpp.ino within the arduino ide and shows a lot of libopencm3 code. That example might be enough for my purposes of experimenting and learning as a beginner with arduino, libopencm3, stm32 and C. I might spend more time with arduino_opencm3 now that serial communication and Serial.println works under my conditions.