Raspberry Pi 3

The Raspberry Pi 3 is an embedded system built and sold by the Raspberry Pi Foundation, Inc. The Raspberry Pi 3 driver provides access to the hardware I/O available on the Raspberry Pi 3 board. The Raspberry Pi 3 includes a BCM2837 ARMv8 Cortex-A53 processor (1.2 GHz, 64-bit, quad-core, 1GB RAM). The I/O available with the Raspberry Pi 3 include:

• 2 PWM output channels
• 28 reconfigurable digital I/O
• 1 general purpose +3.3V serial port*
• 1 SPI port*
• 1 I2C port*
• Integrated with MATLAB/Simulink/Simulink Coder via Quanser QUARC

* Communications channels are accessed through the Stream API blocks, see Serial protocol, SPI protocol and I2C protocol.

The QUARC driver name for this card is raspberry_pi_3 .

To select the Raspberry Pi 3 board, select the QUARC raspberry_pi_3 board type from the drop-down list on the Main tab of the HIL Initialize block. Please note that only one raspberry_pi_3 "card" can be used on a Raspberry Pi 3 at a time. The QUARC controller runs on the Raspberry Pi 3 board and communicates with the hardware I/O directly.

Communications

The communications ports provided on the Raspberry Pi 3 board can be utilized through the QUARC Communications blockset and the Quanser Stream API (see QUARC Communications Protocols).

For SPI communications, a sample URI for communications would be:

spi://localhost:0?baud='1000000',phase='off',lsb='off',frame='0'

where the frame option selects the SPI CE line to frame the SPI bus transaction (0 or 1). Note that the SPI port must be enabled using the raspi-config utility for SPI communications to be used. Once the SPI port is enabled, the corresponding digital I/O (pins 19, 21, 23, 24 and 26) will no longer be available as digital I/O.

SPI can also be enabled via the /boot/config.txt file by setting spi=on in the Device Tree Overlay parameters. For example:

dtparam=spi=on

After changing /boot/config.txt, reboot the Raspberry Pi for the changes to take effect.

For I2C communications, a sample URI for communications would be:

i2c://localhost:0?baud='400000',address=0x69

where the address option specifies the I2C slave address. Note that the I2C port must be enabled using the raspi-config utility for I2C communications to be used. Once the I2C port is enabled, the corresponding digital I/O (pins 3 and 5) will no longer be available as digital I/O.

To set the baud rate for the I2C, the /boot/config.txt file must be edited and the Raspbery Pi rebooted. For example, to enable I2C and set the I2C baud rate to 400000 baud, change the Device Tree Overlay parameters to:

dtparam=i2c_arm=on,i2c_arm_baudrate=400000

After changing /boot/config.txt, reboot the Raspberry Pi for the changes to take effect.

For serial communications, a sample URI for communications would be:

serial://localhost:1?baud='115200',word='8',parity='none',stop='1'

Configuring the Raspberry Pi 3 to support serial communications is a bit more involved. First, use the raspi-config utility to disable the serial port use by the kernel console. Then edit the /boot/config.txt file so that:

enable_uart=1

Also add the line:

dtoverlay=pi3-disable-bt

in order to disable bluetooth, which makes use of the UART otherwise (see Pi Zero W WiFi interference with TTY). Alternatively, to maintain bluetooth and use the UART, use the lines:

dtoverlay=pi3-miniuart.txt

core_freq=250

Refer to this Raspberry Pi forum topic for details.

After changing /boot/config.txt, reboot the Raspberry Pi for the changes to take effect. Use the gpio readall command to confirm that the TxD and RxD pins for the UART are in ALT0 mode. The serial port is /dev/ttyAMA0.

Clocks

The Raspberry Pi 3 card does not support hardware clocks.

Analog Inputs

The Raspberry Pi 3 card does not support analog inputs.

Analog Outputs

The Raspberry Pi 3 card does not support analog outputs.

Digital Inputs

The Raspberry Pi 3 supports 28 bidirectional digital I/O lines. Digital input channel numbers range from 0 to 27. Channels 0 and 1, however, are reserved for a HAT EEPROM I2C interface. A digital I/O line cannot be used as an input and output at the same time. Nor can it be used for communications (SPI, I2C or UART) or PWM at the same time.

Since the digital I/O lines may be individually programmed as inputs or outputs on the Raspberry Pi 3, all channels which will be used for digital inputs should be configured on the HIL Initialize block's Digital Inputs tab. Set the Digital input channels field to all the digital I/O channels that will be used as digital inputs on the board for the current diagram. For example, enter 2:4 to designate channels 2 through 4 as digital inputs. Specify [2, 4, 5] to indicate that channels 2, 4 and 5 are to be configured as digital inputs.

Digital Outputs

The Raspberry Pi 3 supports 28 bidirectional digital I/O lines. Digital output channel numbers range from 0 to 27. Channels 0 and 1, however, are reserved for a HAT EEPROM I2C interface. A digital I/O line cannot be used as an input and output at the same time. Nor can it be used for communications (SPI, I2C or UART) or PWM at the same time.

Since the digital I/O lines may be individually programmed as inputs or outputs on the Raspberry Pi 3, all the channels which will be used for digital outputs should be configured on the HIL Initialize block's Digital Outputs tab. Set the Digital output channels field to all the bidirectional digital I/O channels that will be used as digital outputs on the board for the current diagram. For example, enter 2:4 to designate channels 2 through 4 as digital outputs. Specify [2, 4, 5] to indicate that channels 2, 4 and 5 are to be configured as digital outputs.

To set the digital output values when the model is loaded or unloaded, set the Initial digital outputs and Final digital outputs to the desired values respectively. If the vectors specified in these fields are shorter than the channel vector, the value of the last element in the vector will be used for the rest of the channels. Hence, a scalar value will apply to all channels specified in the Digital output channels field.

Encoder Inputs

The Raspberry Pi 3 card does not support encoder inputs.

PWM Outputs

The Raspberry Pi 3 driver supports up to 2 PWM output channels. Hence, PWM output channels range from 0 to 1. Each PWM channel is completely independent and can have its own duty cycle and frequency.

Before the PWM channels may be used, they must be configured in the /boot/config.txt file and in the board-specific options. The /boot/config.txt file must be edited with root privileges. For example, to use the vi editor, enter the command:

sudo vi /boot/config.txt

in a terminal window.

The lines which must be added to the /boot/config.txt file depend on the number of PWM channels desired, and the pins to which they are assigned. The following table documents the lines that must be added to the /boot/config.txt file for each combination of options:

In order to configure the PWM mode or frequency, or to set the value of the PWM outputs when the model is loaded or unloaded, the PWM outputs must be configured on the HIL Initialize block's PWM Outputs tab. Set the PWM output channels field to all the PWM output channels that will be used on the board for the current diagram. For example, enter 0:1 to indicate channels 0 and 1. Specify 1 to indicate channel 1 alone.

The PWM outputs are generic PWM outputs that are capable of producing the standard analog ESC protocols, namely standard PWM (1000us to 2000us), Oneshot125 (125us to 250us), Oneshot42 (42us to 84us) and Multishot (5us to 25us). They may also be used to drive R/C servos.

The PWM parameters for each of these protocols are tabulated below:

The PWM outputs are not restricted to these parameter values as they are generic PWM outputs. The maximum output frequency is 50 MHz. The number of bits of resolution decreases with increasing PWM output frequency.

Set the PWM output frequency (a.k.a., pulse rate) in the "Frequencies in Hz or duty cycle" field. The PWM output mode is typically set to duty cycle mode (0) or time mode (4) when driving ESCs or R/C servos. Set the Initial PWM outputs and Final PWM outputs fields to the desired initial and final output values respectively. The interpretation of these output values depends on the PWM mode selected. If the vectors specified in these fields are shorter than the channel vector, the value of the last element in the vector will be used for the rest of the channels. Hence, a scalar value will apply to all channels specified in the PWM output channels field.

Other Inputs

The Raspberry Pi 3 card does not support other inputs.

Other Outputs

The Raspberry Pi 3 card does not support other outputs.

Interrupts

The Raspberry Pi 3 card, or its driver, does not support any interrupt sources.

Watchdog

The Raspberry Pi 3 card does not support a watchdog timer.

Board-Specific Options

The Raspberry Pi 3 has a number of board-specific options to control specialized functionality of the board. These options configure the PWM.

pwm0_en

This option is a boolean value that enable or disables PWM 0. If PWM 0 is disabled then the PWM pin may be used as a regular digital I/O. Valid values are 0, 1, false, true, off, on, no or yes.

pwm1_en

This option is a boolean value that enable or disables PWM 1. If PWM 1 is disabled then the PWM pin may be used as a regular digital I/O. Valid values are 0, 1, false, true, off, on, no or yes.

pwm0_pin

This option determines which pin will be used for PWM 0. Valid values are 12 or 18 corresponding to GPIO 12 or GPIO 18 respectively.

pwm1_pin

This option determines which pin will be used for PWM 1. Valid values are 13 or 19 corresponding to GPIO 13 or GPIO 19 respectively.

Properties

The Raspberry Pi 3 card does not support any properties.

Connectors

The Raspberry Pi 3 board has one connector for expansion I/O. The pinouts for this connector are listed below. Note that all pins are 3.3V and are not 5V tolerant unless marked otherwise. Exceeding these voltages may damage the board!

Raspberry Pi GPIO Connector

Legend

Targets

See Also

• Raspberry Pi Zero W

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