mbed API for Raspberry Pi boards.
mbedPi
This is an attempt to implement a limited number of mbed APIs for Raspberry Pi single-board computers. The project was inspired by and based on the arduPi library developed for the Arduino by Cooking Hacks .
Specifications
- Chip: Broadcom BCM2836 SoC
- Core architecture: Quad-core ARM Cortex-A7
- CPU frequency: 900 MHz
- GPU: Dual Core VideoCore IV® Multimedia Co-Processor
- Memory: 1GB LPDDR2
- Operating System: Boots from Micro SD card, running a version of the Linux operating system
- Power: Micro USB socket 5V, 2A
Connectors
- Ethernet: 10/100 BaseT Ethernet socket
- Video Output: HDMI (rev 1.3 & 1.4)
- Audio Output: 3.5mm jack, HDMI
- USB: 4 x USB 2.0 Connector
- GPIO Connector: 40-pin 2.54 mm (100 mil) expansion header: 2x20 strip providing 27 GPIO pins as well as +3.3 V, +5 V and GND supply lines
- Camera Connector: 15-pin MIPI Camera Serial Interface (CSI-2)
- JTAG: Not populated
- Display Connector: Display Serial Interface (DSI) 15 way flat flex cable connector with two data lanes and a clock lane
- Memory Card Slot: Micro SDIO
GPIO connector pinout
Information
Only the labels printed in blue/white or green/white (i.e. p3, gpio2 ...) must be used in your code. The other labels are given as information (alternate-functions, power pins, ...).
Building programs for the Raspberry Pi with mbedPi
I use Qt Creator for development, however you can use any other IDE available on the Raspberry Pi (e.g. Geany) if you like. For a quick try:
- Install Qt and the Qt Creator onto your Raspberry Pi. Then create a new "Blinky" Plain non-Qt C++ Project as follows:
- Change the main code as below:
main.cpp
#include "mbedPi.h" int main() { DigitalOut myled(p7); while(1) { myled = 1; // LED is ON wait(0.2); // 200 ms myled = 0; // LED is OFF wait(1.0); // 1 sec printf("Blink\r\n"); } }
- Copy the mbedPi.zip file into your project's folder and unzip.
- Add the mbedPi.h and mbedPi.cpp files to your project by right clicking on the "Blinky" project and then clicking on the "Add Existing Files..." option in the local menu:
- Double click on Blinky.pro to open it for editing and add new libraries by inserting a new line as follows:
- Compile the project.
- Connect an LED through a 1k resistor to pin 7 and the ground on the Raspberry Pi GPIO connector.
- Run the binary as sudo (sudo ./Blinky) and you should see the LED blinking.
- Press Ctrl+c to stop running the application.
Diff: include/SPI.h
- Revision:
- 1:1f2d9982fa8c
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/include/SPI.h Tue Dec 20 12:08:07 2022 +0000 @@ -0,0 +1,75 @@ +#ifndef _SPI_H_ +#define _SPI_H_ + +#include "BCM2835.h" + +class SPI +{ +public: + /** Create a SPI master connected to the specified pins. + */ + SPI(); + ~SPI(); + + /** Configure the data transmission format. + * + * @param bits Number of bits per SPI frame (4 - 16). + * @param mode Clock polarity and phase mode (0 - 3). + * + * @code + * mode | POL PHA + * -----+-------- + * 0 | 0 0 + * 1 | 0 1 + * 2 | 1 0 + * 3 | 1 1 + * @endcode + */ + void format(int bits, uint8_t mode = 0); + + /** Set the SPI bus clock frequency. + * + * @param hz Clock frequency in Hz (default = 1MHz). + */ + void frequency(int hz); + + /** Write to the SPI Slave and return the response. + * + * @param value Data to be sent to the SPI slave. + * + * @return Response from the SPI slave. + */ + uint8_t write(uint8_t value); + + /** Write to the SPI Slave and obtain the response. + * + * The total number of bytes sent and received will be the maximum of + * tx_length and rx_length. The bytes written will be padded with the + * value 0xff. + * + * @param tx_buffer Pointer to the byte-array of data to write to the device. + * @param tx_length Number of bytes to write, may be zero. + * @param rx_buffer Pointer to the byte-array of data to read from the device. + * @param rx_length Number of bytes to read, may be zero. + * @return + * The number of bytes written and read from the device. This is + * maximum of tx_length and rx_length. + */ + int write(const char* tx_buffer, int tx_length, char* rx_buffer, int rx_length); + + /** Set default write value. + * SPI requires the master to send some data during a read operation. + * Different devices may require different default byte values. + * For example: An SD Card requires default bytes to be 0xFF. + * + * @param data Default character to be transmitted during a read operation. + */ + void set_default_write_value(char value); +private: + uint8_t _write_fill; + + void setClockDivider(uint16_t divider); +}; + +#endif // _SPI_H_ +