Configuration¶
Clocks¶
The microcontroller is configured to use the External High Speed clock (HSE), at 8 MHz, and set the SYSCLK at 72 MHz. The AHB is at 72 MHz as well (the AHB divider is set to 1 by default). The AHB clock is used to generate the SysTick interruptions. For more information have a look at the STM32F10xxx Reference Manual [3].
Bluetooth¶
The robot can communicate with the world using an HC-05 serial bluetooth [1] module. This module is configured with a baud rate of 921600, 8 bits data, 1 stop bit, no parity and no flow control.
Encoders¶
Timers 1 and 4 are configured to read quadrature encoders (and thus, connected to the IE2-512 encoder [2] channels A and B). They are both configured to count on both TI1 and TI2 edges.
Gyroscope¶
Gyros are selected as the clock source for accuracy (versus the internal relaxation oscillator suitable for lower power consumption when only accelerometer is being used).
The MPU-6500 gyro features the following SPI operational features:
- Data is delivered MSB first and LSB last.
- Data is latched on the rising edge of SCLK.
- Data should be transitioned on the falling edge of SCLK.
- The maximum frequency of SCLK is 1 MHz. Although the sensor and interrupt registers may be read using SPI at 20 MHz.
- Read/write operations are completed in 16+ cycles (2+ bytes).
- First byte contains the SPI address, and the following the SPI data.
- First bit of the first byte contains the Read (1) / Write (0) bit.
- The following 7 bits contain the Register Address.
- In cases of multiple-byte read/writes, data is two or more bytes.
Pinout¶
Bluepill¶
| Pin | Function | Type | Connected to |
|---|---|---|---|
| PA0 | ADC12_IN0 | Input | Battery voltage |
| PA1 | N/A | N/A | Not connected |
| PA2 | ADC12_IN2 | Input | Receiver front right |
| PA3 | ADC12_IN3 | Input | Receiver side right |
| PA4 | ADC12_IN4 | Input | Receiver side left |
| PA5 | ADC12_IN5 | Input | Receiver front left |
| PA6 | TIM3_CH1 | Input | Motor driver IN1 (left) |
| PA7 | TIM3_CH2 | Input | Motor driver IN2 (left) |
| PA8 | GPIO | Output | Emitter left front |
| PA9 | GPIO | Output | Emitter left side |
| PA10 | TIM1_CH3 | Output | Speaker signal |
| PA11 | GPIO | Input | Button left |
| PA12 | GPIO | Input | Button right |
| PA15 | TIM2_CH1 | Input | Encoder left, channel A |
| PB0 | TIM3_CH3 | Output | Motor driver IN3 (right) |
| PB1 | TIM3_CH4 | Output | Motor driver IN4 (right) |
| PB3 | TIM2_CH2 | Input | Encoder left, channel B |
| PB4 | GPIO | Output | LED left |
| PB5 | GPIO | Output | LED right |
| PB6 | TIM4_CH1 | Input | Encoder right, channel B |
| PB7 | TIM4_CH2 | Input | Encoder right, channel A |
| PB8 | GPIO | Output | Emitter right side |
| PB9 | GPIO | Output | Emitter right front |
| PB10 | USART3_TX | Output | Bluetooth RX |
| PB11 | USART3_RX | Input | Bluetooth TX |
| PB12 | NSS2 | Output | Gyroscope NCS (SPI-CS) |
| PB13 | SCK2 | Output | Gyroscope SCL (SPI-SCLK) |
| PB14 | MISO2 | Input | Gyroscope AD0 (SPI-SDO) |
| PB15 | MOSI2 | Output | Gyroscope SDA (SPI-SDI) |
| PC13 | N/A | N/A | Not connected |
| PC14 | N/A | N/A | Not connected |
| PC15 | N/A | N/A | Not connected |
Motor driver¶
| Pin | Connected to |
|---|---|
| IN1 | Defined in Bluepill pinout |
| IN2 | Defined in Bluepill pinout |
| IN3 | Defined in Bluepill pinout |
| IN4 | Defined in Bluepill pinout |
| OUT1 | Motor left + (pin 2) |
| OUT2 | Motor left - (pin 1) |
| OUT3 | Motor right - (pin 1) |
| OUT4 | Motor right + (pin 2) |
| EEP | 50 kΩ pull-up to 5V (J2 jumper is open) |
| ULT | Not connected |
| VCC | Vmot |
| GND | GND |
Exceptions¶
The configuration for interruptions (IRQ) and SysTick exceptions has been deduced taking into account that:
- The priority is configurable, the exception and the IRQ numbers are fixed.
- If the software does not configure any priority, then all exceptions with a configurable priority have a priority of 0. We didn’t find any reference on the documentation but for experience it seems that by default SysTick exception has higher priority than any interruption.
- For System Handlers, the lowest priority value has precedence over the lowest exception number value.
- For Interrupt service routines (ISR) the precedence is: lowest group priority value, lowest subpriority value and lowest IRQ number value. For now, there are not any subpriority value configured for this project.
- The preemption happens just for higher priority exceptions (nothing to do with exception number or subpriority).
For more information have a look at the STM32F10xxx/20xxx/21xxx/L1xxxx Cortex®-M3 programming manual [4].
| Exceptions | Handler | Excep num | IRQ num | Priority | Functionality |
|---|---|---|---|---|---|
| SysTick | System | 15 | -1 | 1 | Control and algorithm |
| ADC1_2 | ISR | N/A | 18 | 1 | Battery low level |
| TIM1_UP | ISR | N/A | 25 | 0 | Infrared state machine |
| USART3 | ISR | N/A | 39 | 1 | Bluetooth |
Gyroscope¶
| Pin | Function | Connected to |
|---|---|---|
| SCL | SPI-SCLK | Defined in Bluepill pinout |
| SDA | SPI-SDI | Defined in Bluepill pinout |
| EDA | N/A | Not connected |
| ECL | N/A | Not connected |
| AD0 | SPI-SDO | Defined in Bluepill pinout |
| INT | N/A | Not connected |
| NCS | SPI-CS | Defined in Bluepill pinout |
| FSYNC | N/A | Not connected |
| VCC | Power | 5V |
| GND | Power | GND |
