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: source/BCM2835.cpp
- Revision:
- 1:1f2d9982fa8c
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/source/BCM2835.cpp Tue Dec 20 12:08:07 2022 +0000 @@ -0,0 +1,80 @@ +#include "BCM2835.h" + +extern volatile uint32_t* bcm2835_st; +extern volatile timeval start_program; + +/** + * @brief Reads the System Timer Counter (64-bits) + * @note + * @param + * @retval + */ +uint64_t bcm2835_systimer_read(void) +{ + volatile uint32_t* paddr; + uint32_t hi, lo; + uint64_t st; + + if (bcm2835_st==MAP_FAILED) { + return 0; + } + + paddr = bcm2835_st + BCM2835_ST_CHI/4; + hi = bcm2835_peri_read(paddr); + + paddr = bcm2835_st + BCM2835_ST_CLO/4; + lo = bcm2835_peri_read(paddr); + + paddr = bcm2835_st + BCM2835_ST_CHI/4; + st = bcm2835_peri_read(paddr); + + /* Test for overflow */ + if (st == hi) + { + st <<= 32; + st += lo; + } + else + { + st <<= 32; + paddr = bcm2835_st + BCM2835_ST_CLO/4; + st += bcm2835_peri_read(paddr); + } + return st; +} + +/** + * @brief + * @note + * @param + * @retval + */ +uint64_t us_ticker_read() +{ + struct timeval end_point; + uint64_t elapsedTime; + + // stop timer + + gettimeofday(&end_point, NULL); + + // compute and print the elapsed time in microseconds + //elapsedTime = (end_point.tv_sec - start_program.tv_sec) * 1000000.0; // sec to us + elapsedTime += (end_point.tv_usec - start_program.tv_usec); + return elapsedTime; +} + +/** + * @brief + * @note + * @param + * @retval + */ +void bcm2835_sleep_for_ms(unsigned int millis) +{ + struct timespec sleeper; + + sleeper.tv_sec = (time_t) (millis / 1000); + sleeper.tv_nsec = (long)(millis % 1000) * 1000000; + nanosleep(&sleeper, NULL); +}