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 .

/media/uploads/hudakz/board01.jpg

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

Zoom in /media/uploads/hudakz/mbedpi_pinout02.png

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: /media/uploads/hudakz/newproject.png

  • 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:

    /media/uploads/hudakz/addfiles.png

    /media/uploads/hudakz/addfiles02.png

  • Double click on Blinky.pro to open it for editing and add new libraries by inserting a new line as follows:

    /media/uploads/hudakz/libs.png

  • 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. /media/uploads/hudakz/mbedpi_run.png

  • Press Ctrl+c to stop running the application.
Committer:
hudakz
Date:
Tue Dec 20 12:16:18 2022 +0000
Revision:
2:131555dc6fb7
Parent:
1:1f2d9982fa8c
Mbed API for Raspberry Pi boards equipped with BCM2836 SoC.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
hudakz 1:1f2d9982fa8c 1 #include "mbed.h"
hudakz 1:1f2d9982fa8c 2
hudakz 1:1f2d9982fa8c 3 extern volatile uint32_t *bcm2835_bsc1;
hudakz 1:1f2d9982fa8c 4 extern volatile uint32_t *bcm2835_spi0;
hudakz 1:1f2d9982fa8c 5
hudakz 1:1f2d9982fa8c 6 /**************************************************************************
hudakz 1:1f2d9982fa8c 7 *
hudakz 1:1f2d9982fa8c 8 * SPI Class implementation
hudakz 1:1f2d9982fa8c 9 *
hudakz 1:1f2d9982fa8c 10 **************************************************************************/
hudakz 1:1f2d9982fa8c 11
hudakz 1:1f2d9982fa8c 12 /******************
hudakz 1:1f2d9982fa8c 13 * Public methods *
hudakz 1:1f2d9982fa8c 14 ******************/
hudakz 1:1f2d9982fa8c 15 SPI::SPI() :
hudakz 1:1f2d9982fa8c 16 _write_fill(0xFF)
hudakz 1:1f2d9982fa8c 17 {
hudakz 1:1f2d9982fa8c 18 REV = getBoardRev();
hudakz 1:1f2d9982fa8c 19
hudakz 1:1f2d9982fa8c 20 bcm2835_gpio_fsel(9, BCM2835_GPIO_FSEL_ALT0); // MISO
hudakz 1:1f2d9982fa8c 21 bcm2835_gpio_fsel(10, BCM2835_GPIO_FSEL_ALT0); // MOSI
hudakz 1:1f2d9982fa8c 22 bcm2835_gpio_fsel(11, BCM2835_GPIO_FSEL_ALT0); // CLK
hudakz 1:1f2d9982fa8c 23
hudakz 1:1f2d9982fa8c 24 // Set the SPI CS register to some sensible defaults
hudakz 1:1f2d9982fa8c 25 volatile uint32_t* paddr = bcm2835_spi0 + BCM2835_SPI0_CS / 4;
hudakz 1:1f2d9982fa8c 26 bcm2835_peri_write(paddr, 0); // All 0s
hudakz 1:1f2d9982fa8c 27
hudakz 1:1f2d9982fa8c 28 // Clear TX and RX fifos
hudakz 1:1f2d9982fa8c 29 bcm2835_peri_write_nb(paddr, BCM2835_SPI0_CS_CLEAR);
hudakz 1:1f2d9982fa8c 30 }
hudakz 1:1f2d9982fa8c 31
hudakz 1:1f2d9982fa8c 32 /**
hudakz 1:1f2d9982fa8c 33 * @brief
hudakz 1:1f2d9982fa8c 34 * @note
hudakz 1:1f2d9982fa8c 35 * @param
hudakz 1:1f2d9982fa8c 36 * @retval
hudakz 1:1f2d9982fa8c 37 */
hudakz 1:1f2d9982fa8c 38 SPI::~SPI()
hudakz 1:1f2d9982fa8c 39 {
hudakz 1:1f2d9982fa8c 40 // Set all the SPI0 pins back to input
hudakz 1:1f2d9982fa8c 41
hudakz 1:1f2d9982fa8c 42 // bcm2835_gpio_fsel(7, BCM2835_GPIO_FSEL_INPT); // CE1
hudakz 1:1f2d9982fa8c 43 // bcm2835_gpio_fsel(8, BCM2835_GPIO_FSEL_INPT); // CE0
hudakz 1:1f2d9982fa8c 44 bcm2835_gpio_fsel(9, BCM2835_GPIO_FSEL_INPT); // MISO
hudakz 1:1f2d9982fa8c 45 bcm2835_gpio_fsel(10, BCM2835_GPIO_FSEL_INPT); // MOSI
hudakz 1:1f2d9982fa8c 46 bcm2835_gpio_fsel(11, BCM2835_GPIO_FSEL_INPT); // CLK
hudakz 1:1f2d9982fa8c 47 }
hudakz 1:1f2d9982fa8c 48
hudakz 1:1f2d9982fa8c 49 /**
hudakz 1:1f2d9982fa8c 50 * @brief
hudakz 1:1f2d9982fa8c 51 * @note
hudakz 1:1f2d9982fa8c 52 * @param
hudakz 1:1f2d9982fa8c 53 * @retval
hudakz 1:1f2d9982fa8c 54 */
hudakz 1:1f2d9982fa8c 55 void SPI::format(int bits, uint8_t mode)
hudakz 1:1f2d9982fa8c 56 {
hudakz 1:1f2d9982fa8c 57 volatile uint32_t* paddr = bcm2835_spi0 + BCM2835_SPI0_CS / 4;
hudakz 1:1f2d9982fa8c 58
hudakz 1:1f2d9982fa8c 59 if (bits > 0) {
hudakz 1:1f2d9982fa8c 60 bits = 8U;
hudakz 1:1f2d9982fa8c 61 }
hudakz 1:1f2d9982fa8c 62 //BCM2835_SPI_BIT_ORDER_MSBFIRST is the only one suported by SPI0
hudakz 1:1f2d9982fa8c 63
hudakz 1:1f2d9982fa8c 64 // Mask in the CPO and CPHA bits of CS
hudakz 1:1f2d9982fa8c 65 bcm2835_peri_set_bits(paddr, mode << 2, BCM2835_SPI0_CS_CPOL | BCM2835_SPI0_CS_CPHA);
hudakz 1:1f2d9982fa8c 66 }
hudakz 1:1f2d9982fa8c 67
hudakz 1:1f2d9982fa8c 68 /**
hudakz 1:1f2d9982fa8c 69 * @brief
hudakz 1:1f2d9982fa8c 70 * @note
hudakz 1:1f2d9982fa8c 71 * @param
hudakz 1:1f2d9982fa8c 72 * @retval
hudakz 1:1f2d9982fa8c 73 */
hudakz 1:1f2d9982fa8c 74 void SPI::frequency(int hz)
hudakz 1:1f2d9982fa8c 75 {
hudakz 1:1f2d9982fa8c 76 uint16_t divider = 0;
hudakz 1:1f2d9982fa8c 77
hudakz 1:1f2d9982fa8c 78 if (hz < 8000) {
hudakz 1:1f2d9982fa8c 79 divider = SPI_CLOCK_DIV65536;
hudakz 1:1f2d9982fa8c 80 }
hudakz 1:1f2d9982fa8c 81 else
hudakz 1:1f2d9982fa8c 82 if (hz < 15625) {
hudakz 1:1f2d9982fa8c 83 divider = SPI_CLOCK_DIV32768;
hudakz 1:1f2d9982fa8c 84 }
hudakz 1:1f2d9982fa8c 85 else
hudakz 1:1f2d9982fa8c 86 if (hz < 31250) {
hudakz 1:1f2d9982fa8c 87 divider = SPI_CLOCK_DIV16384;
hudakz 1:1f2d9982fa8c 88 }
hudakz 1:1f2d9982fa8c 89 else
hudakz 1:1f2d9982fa8c 90 if (hz < 62500) {
hudakz 1:1f2d9982fa8c 91 divider = SPI_CLOCK_DIV8192;
hudakz 1:1f2d9982fa8c 92 }
hudakz 1:1f2d9982fa8c 93 else
hudakz 1:1f2d9982fa8c 94 if (hz < 125000) {
hudakz 1:1f2d9982fa8c 95 divider = SPI_CLOCK_DIV4096;
hudakz 1:1f2d9982fa8c 96 }
hudakz 1:1f2d9982fa8c 97 else
hudakz 1:1f2d9982fa8c 98 if (hz < 250000) {
hudakz 1:1f2d9982fa8c 99 divider = SPI_CLOCK_DIV2048;
hudakz 1:1f2d9982fa8c 100 }
hudakz 1:1f2d9982fa8c 101 else
hudakz 1:1f2d9982fa8c 102 if (hz < 500000) {
hudakz 1:1f2d9982fa8c 103 divider = SPI_CLOCK_DIV1024;
hudakz 1:1f2d9982fa8c 104 }
hudakz 1:1f2d9982fa8c 105 else
hudakz 1:1f2d9982fa8c 106 if (hz < 1000000) {
hudakz 1:1f2d9982fa8c 107 divider = SPI_CLOCK_DIV512;
hudakz 1:1f2d9982fa8c 108 }
hudakz 1:1f2d9982fa8c 109 else
hudakz 1:1f2d9982fa8c 110 if (hz < 2000000) {
hudakz 1:1f2d9982fa8c 111 divider = SPI_CLOCK_DIV256;
hudakz 1:1f2d9982fa8c 112 }
hudakz 1:1f2d9982fa8c 113 else
hudakz 1:1f2d9982fa8c 114 if (hz < 4000000) {
hudakz 1:1f2d9982fa8c 115 divider = SPI_CLOCK_DIV128;
hudakz 1:1f2d9982fa8c 116 }
hudakz 1:1f2d9982fa8c 117 else
hudakz 1:1f2d9982fa8c 118 if (hz < 8000000) {
hudakz 1:1f2d9982fa8c 119 divider = SPI_CLOCK_DIV64;
hudakz 1:1f2d9982fa8c 120 }
hudakz 1:1f2d9982fa8c 121 else
hudakz 1:1f2d9982fa8c 122 if (hz < 20000000) {
hudakz 1:1f2d9982fa8c 123 divider = SPI_CLOCK_DIV32;
hudakz 1:1f2d9982fa8c 124 }
hudakz 1:1f2d9982fa8c 125 else
hudakz 1:1f2d9982fa8c 126 if (hz < 40000000) {
hudakz 1:1f2d9982fa8c 127 divider = SPI_CLOCK_DIV16;
hudakz 1:1f2d9982fa8c 128 }
hudakz 1:1f2d9982fa8c 129 else
hudakz 1:1f2d9982fa8c 130 if (hz < 80000000) {
hudakz 1:1f2d9982fa8c 131 divider = SPI_CLOCK_DIV8;
hudakz 1:1f2d9982fa8c 132 }
hudakz 1:1f2d9982fa8c 133 else
hudakz 1:1f2d9982fa8c 134 if (hz < 160000000) {
hudakz 1:1f2d9982fa8c 135 divider = SPI_CLOCK_DIV4;
hudakz 1:1f2d9982fa8c 136 }
hudakz 1:1f2d9982fa8c 137 else {
hudakz 1:1f2d9982fa8c 138
hudakz 1:1f2d9982fa8c 139 // hz >= 160000000
hudakz 1:1f2d9982fa8c 140 divider = SPI_CLOCK_DIV2;
hudakz 1:1f2d9982fa8c 141 }
hudakz 1:1f2d9982fa8c 142
hudakz 1:1f2d9982fa8c 143 setClockDivider(divider);
hudakz 1:1f2d9982fa8c 144 }
hudakz 1:1f2d9982fa8c 145
hudakz 1:1f2d9982fa8c 146 /**
hudakz 1:1f2d9982fa8c 147 * @brief
hudakz 1:1f2d9982fa8c 148 * @note
hudakz 1:1f2d9982fa8c 149 * @param
hudakz 1:1f2d9982fa8c 150 * @retval
hudakz 1:1f2d9982fa8c 151 */
hudakz 1:1f2d9982fa8c 152 uint8_t SPI::write(uint8_t value)
hudakz 1:1f2d9982fa8c 153 {
hudakz 1:1f2d9982fa8c 154 volatile uint32_t* paddr = bcm2835_spi0 + BCM2835_SPI0_CS / 4;
hudakz 1:1f2d9982fa8c 155 volatile uint32_t* fifo = bcm2835_spi0 + BCM2835_SPI0_FIFO / 4;
hudakz 1:1f2d9982fa8c 156
hudakz 1:1f2d9982fa8c 157 bcm2835_peri_set_bits(paddr, BCM2835_SPI0_CS_CLEAR, BCM2835_SPI0_CS_CLEAR);
hudakz 1:1f2d9982fa8c 158
hudakz 1:1f2d9982fa8c 159 bcm2835_peri_set_bits(paddr, BCM2835_SPI0_CS_TA, BCM2835_SPI0_CS_TA);
hudakz 1:1f2d9982fa8c 160
hudakz 1:1f2d9982fa8c 161 while (!(bcm2835_peri_read(paddr) & BCM2835_SPI0_CS_TXD))
hudakz 1:1f2d9982fa8c 162 wait_us(10);
hudakz 1:1f2d9982fa8c 163
hudakz 1:1f2d9982fa8c 164 bcm2835_peri_write_nb(fifo, value);
hudakz 1:1f2d9982fa8c 165
hudakz 1:1f2d9982fa8c 166 while (!(bcm2835_peri_read_nb(paddr) & BCM2835_SPI0_CS_DONE))
hudakz 1:1f2d9982fa8c 167 wait_us(10);
hudakz 1:1f2d9982fa8c 168
hudakz 1:1f2d9982fa8c 169 uint32_t ret = bcm2835_peri_read_nb(fifo);
hudakz 1:1f2d9982fa8c 170
hudakz 1:1f2d9982fa8c 171 bcm2835_peri_set_bits(paddr, 0, BCM2835_SPI0_CS_TA);
hudakz 1:1f2d9982fa8c 172
hudakz 1:1f2d9982fa8c 173 return ret;
hudakz 1:1f2d9982fa8c 174 }
hudakz 1:1f2d9982fa8c 175
hudakz 1:1f2d9982fa8c 176 /**
hudakz 1:1f2d9982fa8c 177 * @brief
hudakz 1:1f2d9982fa8c 178 * @note
hudakz 1:1f2d9982fa8c 179 * @param
hudakz 1:1f2d9982fa8c 180 * @retval
hudakz 1:1f2d9982fa8c 181 */
hudakz 1:1f2d9982fa8c 182 int SPI::write(const char* tx_buffer, int tx_length, char* rx_buffer, int rx_length)
hudakz 1:1f2d9982fa8c 183 {
hudakz 1:1f2d9982fa8c 184 int len = tx_length;
hudakz 1:1f2d9982fa8c 185 if (rx_length > len)
hudakz 1:1f2d9982fa8c 186 len = rx_length;
hudakz 1:1f2d9982fa8c 187
hudakz 1:1f2d9982fa8c 188 volatile uint32_t* paddr = bcm2835_spi0 + BCM2835_SPI0_CS / 4;
hudakz 1:1f2d9982fa8c 189 volatile uint32_t* fifo = bcm2835_spi0 + BCM2835_SPI0_FIFO / 4;
hudakz 1:1f2d9982fa8c 190
hudakz 1:1f2d9982fa8c 191 // This is Polled transfer as per section 10.6.1
hudakz 1:1f2d9982fa8c 192
hudakz 1:1f2d9982fa8c 193 // BUG ALERT: what happens if we get interupted in this section, and someone else
hudakz 1:1f2d9982fa8c 194 // accesses a different peripheral?
hudakz 1:1f2d9982fa8c 195 // Clear TX and RX fifos
hudakz 1:1f2d9982fa8c 196 bcm2835_peri_set_bits(paddr, BCM2835_SPI0_CS_CLEAR, BCM2835_SPI0_CS_CLEAR);
hudakz 1:1f2d9982fa8c 197
hudakz 1:1f2d9982fa8c 198 // Set TA = 1
hudakz 1:1f2d9982fa8c 199 bcm2835_peri_set_bits(paddr, BCM2835_SPI0_CS_TA, BCM2835_SPI0_CS_TA);
hudakz 1:1f2d9982fa8c 200
hudakz 1:1f2d9982fa8c 201 int i;
hudakz 1:1f2d9982fa8c 202 for (i = 0; i < len; i++) {
hudakz 1:1f2d9982fa8c 203
hudakz 1:1f2d9982fa8c 204 // Maybe wait for TXD
hudakz 1:1f2d9982fa8c 205 while (!(bcm2835_peri_read(paddr) & BCM2835_SPI0_CS_TXD))
hudakz 1:1f2d9982fa8c 206 wait_us(10);
hudakz 1:1f2d9982fa8c 207
hudakz 1:1f2d9982fa8c 208 // Write to FIFO, no barrier
hudakz 1:1f2d9982fa8c 209 if (i < tx_length)
hudakz 1:1f2d9982fa8c 210 bcm2835_peri_write_nb(fifo, tx_buffer[i]);
hudakz 1:1f2d9982fa8c 211 else
hudakz 1:1f2d9982fa8c 212 bcm2835_peri_write_nb(fifo, _write_fill);
hudakz 1:1f2d9982fa8c 213
hudakz 1:1f2d9982fa8c 214 // Wait for RXD
hudakz 1:1f2d9982fa8c 215 while (!(bcm2835_peri_read(paddr) & BCM2835_SPI0_CS_RXD))
hudakz 1:1f2d9982fa8c 216 wait_us(10);
hudakz 1:1f2d9982fa8c 217
hudakz 1:1f2d9982fa8c 218 // then read the data byte
hudakz 1:1f2d9982fa8c 219 if (i < rx_length)
hudakz 1:1f2d9982fa8c 220 rx_buffer[i] = bcm2835_peri_read_nb(fifo);
hudakz 1:1f2d9982fa8c 221 else
hudakz 1:1f2d9982fa8c 222 bcm2835_peri_read_nb(fifo);
hudakz 1:1f2d9982fa8c 223 }
hudakz 1:1f2d9982fa8c 224
hudakz 1:1f2d9982fa8c 225 // Wait for DONE to be set
hudakz 1:1f2d9982fa8c 226 while (!(bcm2835_peri_read_nb(paddr) & BCM2835_SPI0_CS_DONE))
hudakz 1:1f2d9982fa8c 227 wait_us(10);
hudakz 1:1f2d9982fa8c 228
hudakz 1:1f2d9982fa8c 229 // Set TA = 0, and also set the barrier
hudakz 1:1f2d9982fa8c 230 bcm2835_peri_set_bits(paddr, 0, BCM2835_SPI0_CS_TA);
hudakz 1:1f2d9982fa8c 231
hudakz 1:1f2d9982fa8c 232 return len;
hudakz 1:1f2d9982fa8c 233 }
hudakz 1:1f2d9982fa8c 234
hudakz 1:1f2d9982fa8c 235 /**
hudakz 1:1f2d9982fa8c 236 * @brief
hudakz 1:1f2d9982fa8c 237 * @note
hudakz 1:1f2d9982fa8c 238 * @param
hudakz 1:1f2d9982fa8c 239 * @retval
hudakz 1:1f2d9982fa8c 240 */
hudakz 1:1f2d9982fa8c 241 void SPI::set_default_write_value(char value)
hudakz 1:1f2d9982fa8c 242 {
hudakz 1:1f2d9982fa8c 243 _write_fill = value;
hudakz 1:1f2d9982fa8c 244 }
hudakz 1:1f2d9982fa8c 245
hudakz 1:1f2d9982fa8c 246 /**
hudakz 1:1f2d9982fa8c 247 * @brief
hudakz 1:1f2d9982fa8c 248 * @note The divisor must be a power of 2. Odd numbers rounded down.
hudakz 1:1f2d9982fa8c 249 * The maximum SPI clock rate is of the APB clock.
hudakz 1:1f2d9982fa8c 250 * @param divider Defaults to 0, which means a divider of 65536.
hudakz 1:1f2d9982fa8c 251 * @retval
hudakz 1:1f2d9982fa8c 252 */
hudakz 1:1f2d9982fa8c 253 void SPI::setClockDivider(uint16_t divider)
hudakz 1:1f2d9982fa8c 254 {
hudakz 1:1f2d9982fa8c 255 volatile uint32_t* paddr = bcm2835_spi0 + BCM2835_SPI0_CLK / 4;
hudakz 1:1f2d9982fa8c 256 bcm2835_peri_write(paddr, divider);
hudakz 1:1f2d9982fa8c 257 }
hudakz 1:1f2d9982fa8c 258
hudakz 1:1f2d9982fa8c 259