Embedded Programming

The STM32F103xx medium-density performance line family incorporates the high-performance ARM®Cortex®-M3 32-bit RISC core operating at a 72 MHz frequency, high-speed embedded memories (Flash memory up to 128 Kbytes and SRAM up to 20 Kbytes), and an extensive range of enhanced I/Os and peripherals connected to two APB buses. All devices offer two 12-bit ADCs, three general purpose 16-bit timers plus one PWM timer, as well as standard and advanced communication interfaces: up to two I2Cs and SPIs, three USARTs, an USB and a CAN.

Specifications:

ARM®32-bit Cortex®-M3 CPU Core

• 72 MHz maximum frequency,1.25 DMIPS/MHz (Dhrystone 2.1) performance at 0 wait state memory access
• Single-cycle multiplication and hardware division



Memories

• 64 or 128 Kbytes of Flash memory
• 20 Kbytes of SRAM



Clock, reset and supply management

• 2.0 to 3.6 V application supply and I/Os
• POR, PDR, and programmable voltage detector (PVD)
• 4-to-16 MHz crystal oscillator
• Internal 8 MHz factory-trimmed RC
• Internal 40 kHz RC
• PLL for CPU clock
• 32 kHz oscillator for RTC with calibration



Low-power

• Sleep, Stop and Standby modes
• VBAT supply for RTC and backup registers

2 x 12-bit, 1 μs A/D converters (up to 16 channels)



• Conversion range: 0 to 3.6 V
• Dual-sample and hold capability
• Temperature sensor



DMA

• 7-channel DMA controller
• Peripherals supported: timers, ADC, SPIs, I2Cs and USARTs



Up to 80 fast I/O ports

• 26/37/51/80 I/Os, all mappable on 16 external interrupt vectors and almostall 5 V-tolerant



Debug mode

• Serial wire debug (SWD) & JTAG interfaces



7 timers

• Three 16-bit timers, each with up to 4 IC/OC/PWM or pulse counter and
quadrature (incremental) encoder input
• 16-bit, motor control PWM timer with dead-time generation and emergency
stop
• 2 watchdog timers (Independent and Window)
• SysTick timer 24-bit downcounter



Up to 9 communication interfaces

• Up to 2 x I2C interfaces (SMBus/PMBus)
• Up to 3 USARTs (ISO 7816 interface, LIN, IrDA capability, modem control)
• Up to 2 SPIs (18 Mbit/s)
• CAN interface (2.0B Active)
• USB 2.0 full-speed interface



CRC calculation unit, 96-bit unique ID

Packages are ECOPACK®

The STM32F103C8T6 development board comes with all peripheral components on board and Serial/USB and SWIM interface for programming and getting the onboard STM32F103C8T6 chip to work.
All information on these generic STM32F103C8T6 development board, also known as the Blue Pill development board can be found here.

To program the generic blue pill development board I have, I'll be using STM32duino, the arduino Core for STM32.
Installation instructions can be found here.

To use the board manager installation method, the following url needs to be added to the Additional Board Manager URLs,
https://github.com/stm32duino/BoardManagerFiles/raw/master/STM32/package_stm_index.json

Blue Pill ---------------------ST-Link

• 3v3--------------------------------------pin 1
• SWO------------------------------------ pin 7
• SWCLK-----------------------------------pin 9
• GND-------------------------------------GND

Code:

Hex footprint:

Surprisingly, the hex footprint to run this small code is 715 lines long. (32,768 bytes)

Mbed is an online embedded device platform which gives you an embedded operating system, transport, security and cloud services to create Embedded solutions. Although it is designed mostly for IoT applications, the generic chinese blue pill development board can also be programmed using it. I think it is an integrated solution that is easy to work on and easy to deploy. More about what is Mbed and how it works, can be found here.

Adding Hardware for Generic Blue Pill in our console:

After you sign up, You should be able to navigate to your console.Before we can get started with programming, we need to add our device to the hardware list in our console. The generic blue pill development board for the STM32F103C8T6 is not supported officially by mbed. So we have to add it as a Nucleo-F103RB. It uses the same chip but has 128kb flash memory instead of our 64kb board. I found this nifty guide, on how to program our generic board using Mbed.

Using the Online Mbed Compiler

The compiler UI is a bit confusing at first. I would recomend using the many example programs given by Mbed and writing your own code by modifying the templates. First we'll create a new program, and I named it "HelloWorld_blinky" and is based on the 'Display a message on PC using UART' example.
The program project folder will be created along with the 'main.c' file, which we will be editing to write our own code. The example code looks a bit like this, but it didn't work out of the box because the default Serial Tx/Rx pins for the nucleo and the blue pill are different. So after going through the Generic Blue Pill Guide for Mbed, I wrote the following code.

Compiling and optimizing:

The Blue Pill board has 64KB memory, while the nucleo has 128kb. So after we click compile, we have to check on the 'Build Details', and manually ensure the Flash size does not exceed 64kb. For our case, the Flash Size of the build was 27.6kb which was well under 64kb. Once you click compile, the compiled .bin file should automatically downloaded in your browser.

Blue Pill ---------------------ST-Link

• 3v3--------------------------------------pin 1
• SWO------------------------------------ pin 7
• SWCLK-----------------------------------pin 9
• GND-------------------------------------GND

To view the UART output, connect the FTDI module with the blue pill dev. board, make sure the FTDI is in 3.3v mode or you'll destroy the board. The connection should be;

Blue Pill ---------------------FTDI

• 3v3--------------------------------------3.3v
• A3--------------------------------------- TX
• A2----------------------------------------RX
• GND-------------------------------------GND