Zoltan Hudak / Mbed 2 deprecated STM32F103C8T6_Hello Featured

Using low cost Bluepill (STM32F103C8T6) boards with mbed.

Dependencies:   mbed

Dependents:   STM32F103C8T6_Chicharronera_4CV2 STM32F103C8T6_Portada

STM32F103C8T6 board, alias Bluepill

It provides an affordable (about $2 on eBay) and flexible way for users to try out new ideas and build prototypes. The board is equipped with an STM32F103C8T6 microcontroller compatible with the NUCLEO-F103RB platform.

Microcontroller features

• STM32F103C8T6 in LQFP48 package
• ARM®32-bit Cortex®-M3 CPU
• 72 MHz max CPU frequency
• VDD from 2.0 V to 3.6 V
• 64 KB Flash
• 20 KB SRAM
• GPIO (32) with external interrupt capability
• 12-bit ADC (2) with 10 channels
• RTC
• Timers (4)
• I2C (2)
• USART (3)
• SPI (2)
• USB 2.0 full-speed
• CAN

Board features

• Small foot-print
• Flexible board power supply: USB VBUS or external source (3.3V, 5V)
• User LED: LED1
• One push button: RESET
• Programming/Debug port
• Micro-B USB connector
  
  

Board pinout

Zoom in


Maximum allowed I/O voltage levels (next to pin names) are courtesy of Thor Sten to help you avoid board damage. For more details on pin definitions see Table 5 in the Datasheet.

LED1=PC_13  SERIAL_TX=PA_2  I2C_SCL=PB_8  SPI_MOSI=PA_7  PWM_OUT=PB_3
            SERIAL_RX=PA_3  I2C_SDA=PB_9  SPI_MISO=PA_6
                                          SPI_SCK =PA_5
                                          SPI_CS  =PB_6

Schematic

Zoom in

Eagle CAD library

Schematic	Board

Because neither lbr nor zip files can be uploaded to mbed wiki pages anymore, to download the Eagle CAD library right-click on the following link eagle library and select Save link as.... Once saved to your local drive, change the extension from png to lbr.

Using the mbed online compiler to build programs for the STM32F103C8T6 board

Create a program as if it was for a NUCLEO-F103RB board (select NUCLEO-F103RB as target platform for the online compiler).
Or click here to import this demo into your online compiler.

#include "mbed.h"

Serial      pc(PA_2, PA_3); // TX, RX
DigitalOut  myled(PC_13);   // on-board LED
  
int main() 
{  
    while(1) {
        // The on-board LED is connected via a resistor to +3.3V (not to GND). 
        // So the LED is active on 0
        myled = 0;      // turn the LED on
        wait_ms(200);   // wait 200 millisecond
        myled = 1;      // turn the LED off
        pc.printf("Blink\r\n");
        wait_ms(1000);  // wait 1000 millisecond
    }
}

Programming the STM32F103C8T6 board

NUCLEO ST-LINK/V2-1 and drag & drop

You can use the NUCLEO virtual disk to program the STM32F103C8T6 board (drag and drop programming). To do that, an additional NUCLEO board is needed (any type equipped with ST-LINK/V2-1 will do).

• Remove the two jumpers from the CN2 connector as illustrated in Figure 8:
  
  

• Connect the NUCLEO board CN4 connector to the STM32F103C8T6 board using flying wires as follows:

• Provide power for the STM32F103C8T6 board through a 3.3V pin, 5V pin or over a USB cable. (The VDD_TARGET pin on the NUCLEO board CON4 does not work as source of power).
  
  
• Connect the NUCLEO board to your PC over a USB cable.
  
  
• To program the STM32F103C8T6 board, click on the Compile button and save the binary to the NUCLEO virtual disk .
  For more details have a look at the User Manual, chapter 6.2.4 Using ST-LINK/V2-1 to program and debug an external STM32 application.
  
  

ST-Link V2 USB dongle and STM32 ST-LINK utility

If you would like to use an ST-Link V2 USB dongle (aka ST-Link V2 Programming Unit) to program the board apply the same wiring as specified above. If not done yet install an ST-Link/V2 driver onto your PC. Plug the ST-Link V2 dongle into your PC. Then click on the Compile button and save the binary to your local disk. Install and run the STM32 ST-LINK utility. Once the program is running open the binary built with the online compiler and click on the Program verify button.

STM32 USART system memory bootloader and Flasher-STM32

Have a look at STM32 Embedded Bootloader.

Download: FLASHER-STM32
For more details read: Appliction Note AN2606.

Using serial port (not just for debugging)

• Connect an FTDI or similar USB to Serial TTL converter to your PC and to an on-board serial port (for example PA_2, PA_3). Make sure you connect the on-board TX pin to the converter's RX pin and the on-board RX pin to the converter's TX pin.

Zoom in

• In your code, create a Serial object (using TX and RX pin names of the connected serial port).

• Use printf function to send serial messages to the connected PC.
  
  

#include "mbed.h" 

// declarations needed to change the parameters of stdio UART 
extern serial_t     stdio_uart; 
extern int          stdio_uart_inited; 

int main() {
    serial_init(&stdio_uart, PA_9, PA_10); // other than Serial2
    stdio_uart_inited = 1; 
    printf("Ready for debugging\r\n");
}

Additional examples

• Reading analog input
• DS1820 temperature sensor
• Driving Text LCD
• Driving Nokia 5110 LCD
• Driving ILI9341 TFT Display
• A USB serial device
• CAN bus with mbed boards
• Tiny HTTP server with ENC28J60 Ethernet module
• Using SD Card
• Jogpad for the Mach 3 CNC control software
• How to turn kids' old piano toy to a MIDI keyboard

Working offline

• The Mbed Studio IDE is a great tool for working offline. It supports Mbed OS 5 (with built-in Mbed RTOS threads, mutexes, semafores ...) and also Mbed OS 5 Bare metal profile (no RTOS, similar to Mbed OS 2) which is suitable for small or medium size projects requiring less RAM and Flash. To use it, add a mbed_app.json configuration file to your project:

{
    "requires": ["bare-metal"]
}

• Another alternative is to stay with Mbed 2 (aka Mbed classic) and use the QtCreator IDE for building offline.
  

Works great on Linux (Ubuntu) and MS Windows. It's fully integrated with Mbed CLI and supprots all the Mbed enabled targets. To build for the Blue Pill you can select BLUEPILL_F103C8 or NUCLEO_F103RB as your target, depending on the Flash size actually available on your Blue Pill board. To reduce the size of used static RAM and Flash try to select the small library for your project rather than the standard one. That can be achieved by modifying the mbed_app.json file (Ctrl+O) as below:

{
    "target_overrides": {
        "*": {
            "target.default_lib": "small"
        }
    }
}

For more details visit Building offline with QtCreator IDE.

Happy coding :-)