PEB-D-RPI Expansion Board

The phyCORE-i.MX7 development kit includes a PEB-D-RPI Expansion Board designed to facilitate the easy evaluation of certain interfaces available on the kit. The following sections will detail how to use these features in the environments in which they are supported. These instructions assume that you have a properly connected Expansion Board (included with your kit) and have booted into a supported environment (U-Boot and/or Linux) using BSP version PD18.2.0 or newer. If you are looking for information regarding Raspberry Pi HAT support, please see Raspberry Pi HAT.

See the end of this guide for further information about the configuration of signals that get passed to the PEB_D_RPI Expansion Board. 

PEB-D-RPI Expansion Board Interfaces

Use the following image as a reference for the connector interfaces on the PEB-D-RPI Expansion Board used in this document.

USB to Serial UART Interface

The phyCORE-i.MX7 is already configured by default to use UART1 for console input and output over the PEB-D-RPI Expansion Board's X6 micro-USB connector. This connector allows for the use of both UART1 and UART2 for serial data, however only UART1 is configured in the BSP by default because UART2 is reserved for the M4 core in PHYTEC's FreeRTOS software.

4KB EEPROM

This Expansion Board allows you to use the I²C4 interface to write and read small amounts of persistent data to and from an on-board EEPROM. The EEPROM is registered under the 'i2c4' node in the Expansion Board Linux device tree file 'imx7-peb-d-rpi.dtsi' and is accessible as a file in Linux's sysfs directory structure.

• To write to and read from the 4KB EEPROM on the Expansion Board, run the following commands on the target:

  Target (Linux)

  echo 'Testing EEPROM!!' > /sys/class/i2c-dev/i2c-3/device/3-0056/eeprom
  hexdump -c -n 16 /sys/class/i2c-dev/i2c-3/device/3-0056/eeprom

  CODE

• You should see the values you wrote to the EEPROM displayed on your console in hexdump format.

Buttons

The buttons S1 and S2 serve as an example of using GPIO pins as inputs to facilitate user input. The two buttons are registered under their own node, 'phytec_buttons', in the Expansion Board Linux device tree file 'imx7-peb-d-rpi.dtsi' and their status is accessible in Linux's debugfs directory structure. 

• Use the following command to read the state of the buttons S1 and S2 on the PED-D-RPI Expansion Board: 

  Target (Linux)

  cat /sys/kernel/debug/gpio | grep "pebdrpi_button"

  CODE
• You should see the current state of the GPIO pins connected to the active-low buttons displayed on your console.
• Use the above command again while pressing and holding either of the buttons and notice that the state is now pulled high.

LEDs

The LEDs D1 and D2 serve as an example of using GPIO pins as outputs to control a device or devices. The two LEDs are registered under their own node, 'phytec_leds', in the Expansion Board Linux device tree file 'imx7-peb-d-rpi.dtsi' and their status and control are accessible in Linux's sysfs directory structure.

• To turn the LEDs on and off, run the following commands on the target:

  Target (Linux)

  echo 0 > /sys/class/leds/pebdrpi_led_1/brightness
  echo 1 > /sys/class/leds/pebdrpi_led_1/brightness
  echo 0 > /sys/class/leds/pebdrpi_led_2/brightness
  echo 1 > /sys/class/leds/pebdrpi_led_2/brightness

  CODE

• You should see the individual LEDs turn off and on based upon which LED you echoed.

• If you would like to impress your friends or co-workers with your technical prowess...

   Make an LED light show!

  • Open a text editor to write a script: 

    Target (Linux)

    vi ~/lightShow.sh

    CODE

  • Enter the following and save the file: 

    Vi Text Editor

    #!/bin/bash
    
    for i in `seq 1 20`; do
    	echo 0 > /sys/class/leds/pebdrpi_led_1/brightness
    	echo 1 > /sys/class/leds/pebdrpi_led_2/brightness
    	sleep 0.5
    	echo 1 > /sys/class/leds/pebdrpi_led_1/brightness
    	echo 0 > /sys/class/leds/pebdrpi_led_2/brightness
    	sleep 0.5
    done
    echo 0 > /sys/class/leds/pebdrpi_led_1/brightness

    CODE
    

    The vi text editor begins in "Command Mode" and you must first hit the 'i' key in order to enter "Insert Mode". Using the arrow keys to navigate, make the necessary changes and then hit ESC to go back to "Command mode". Now enter ":wq" to write the file and quit.

    
    

    Pro Tip: Use the right click on your mouse to paste. This will only work if you are in "Insert Mode" first.

  • Change the permissions in order to execute the script: 

    Target (Linux)

    chmod +x ~/lightShow.sh

    CODE

  • Now run the script in the background: 

    Target (Linux)

    ~/lightShow.sh &

    CODE

  • The light show will end automatically after approximately 20 seconds. To end it early you can enter the following command: 

    Target (Linux)

    killall lightShow.sh

    CODE

Raspberry Pi-compatible 40-pin Header

The header X11 provides Raspberry Pi HAT hardware support and a convenient location to connect to GPIO or other interface signals that are routed to the Expansion Board. If you are looking for information regarding Raspberry Pi HAT support, please see Raspberry Pi HAT.

GPIO and Interface Signals Map

The following tables show the GPIO bank, pins, and Raspberry Pi-compatible interface signals mapped to the 40-pin header on the PEB-D-RPI Expansion Board:

The pin functions highlighted in blue are fixed and can not or should not be changed.

Jumpers

The 40-pin header also utilizes soldered jumpers to toggle the selection of specific Raspberry Pi-compatible interface signals to certain pins, enabling support of different Raspberry Pi HATs. The following table details the pins and signals that the jumpers control:

Toggling GPIOs Connected to 40-pin Header

When a Raspberry Pi HAT isn't connected, you can use PHYTEC's RPi.GPIO Python library (included with BSP version PD18.2.0 or later) to control GPIOs connected to the 40-pin header. By default, only the following pins are configured for GPIO use in the PEB-D-RPI device tree file: 7, 11, 12, 13, 15, 16, 18, 22, 29, 32, 35, 40. For information on how to enable more GPIOs, please reference Raspberry Pi HAT.

To set pin 7 on the 40-pin header to be a GPIO output and toggle its value, open your Python interpreter by using the following command: 

python

Now in the Python Interpreter, enter the following:

import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BOARD)
GPIO.setup(7, GPIO.OUT)
GPIO.output(7, GPIO.HIGH)
GPIO.output(7, GPIO.LOW)
GPIO.cleanup()
exit()

Using a digital multimeter or other suitable device (such as an LED), you can see the value on pin 7 of the 40-pin header go from 0 to 3.3 V and back to 0 V using the above code. You can also toggle GPIOs using the libgpiod utilities installed to the BSP file system. To toggle the same pin using libgpiod utilities, run the following commands on the target:

gpioset 3 21=1
gpioset 3 21=0

The above commands toggle GPIO chip 4, pin 21, which is routed to pin 7 of the 40-pin header on the PEB-D-RPI Expansion Board.

ARM JTAG 20-pin Debug Interface Header

The header X5 allows you to connect an ARM JTAG 20-pin compatible debugger to the phyCORE-i.MX7. PHYTEC has tested the JTAG interface using an ARM DSTREAM debugger with ARM DS-5 Development Studio and has also verified functionality using a J-Link Debugger Probe with SEGGER's Ozone Debugging Software. You will need to reference the documentation provided by the manufacturer of your debugger to configure and connect your debugger to the debug header. For more information about JTAG see JTAG

Un-populated Expansion Signal Pin Headers

The un-populated headers X12 and X13 can be used to access Expansion Board signals that are not brought out to the Raspberry Pi-compatible 40-pin header. The following tables show the signals brought out to the un-populated headers:

 Advanced Signal Configurations

The expansion connector X16 on the phyBOARD-i.MX7 Carrier Board provides a way to implement custom expansion boards for extended functionality and development. Standard interfaces such as UART, SPI, I²C, and various GPIO are available at the expansion connector and therefore are accessible on the PEB-D-RPI Expansion Board on the phyCORE-i.MX7 development kit. 

Due to the small footprint of the solder jumpers, we recommend using caution when modifying these. Please contact our sales team if you require any options beyond the default configuration.

There are 12 jumpers on the phyBOARD-i.MX7 development kit that are comprised of four solder pads, which provide the option of routing the RGMII2 signals out to the expansion connector rather than to the phyBOARD-i.MX7 Carrier Board's Ethernet PHY.

J9	1+2, 3+4 (Default)	X_RGMII2_RXD0 is routed to the ETH2 phy. X_SNVS_TAMPER1 is routed to the expansion connector at EXP_CONN_MUX1.
	2+3	X_RGMII2_RXD0 is routed to the expansion connector at EXP_CONN_MUX1. X_SNVS_TAMPER1 is not connected to the expansion connector.
J10	1+2, 3+4 (Default)	X_RGMII2_RXD1 is routed to the ETH2 phy. X_SNVS_TAMPER2 is routed to the expansion connector at EXP_CONN_MUX2.
	2+3	X_RGMII2_RXD1 is routed to the expansion connector at EXP_CONN_MUX2. X_SNVS_TAMPER2 is not connected to the expansion connector.
J11	1+2, 3+4 (Default)	X_RGMII2_RXD2 is routed to the ETH2 phy. X_SD1_RESET_B is routed to the expansion connector at EXP_CONN_MUX3.
	2+3	X_RGMII2_RXD2 is routed to the expansion connector at EXP_CONN_MUX3. X_SD1_RESET_B is not connected to the expansion connector.
J12	1+2, 3+4 (Default)	X_RGMII2_RXD3 is routed to the ETH2 phy. X_GPIO1_O9 is routed to the expansion connector at EXP_CONN_MUX4.
	2+3	X_RGMII2_RXD3 is routed to the expansion connector at EXP_CONN_MUX4. X_GPIO1_09 is not connected to the expansion connector.
J13	1+2, 3+4 (Default)	X_RGMII2_RX_CTL is routed to the ETH2 phy. X_GPIO2_15 is routed to the expansion connector at EXP_CONN_MUX5.
	2+3	X_RGMII2_RX_CTL is routed to the expansion connector at EXP_CONN_MUX5. X_GPIO2_15 is not connected to the expansion connector.
J14	1+2, 3+4 (Default)	X_RGMII2_RXC is routed to the ETH2 phy. X_LCD1_RESET is routed to the expansion connector at EXP_CONN_MUX6.
	2+3	X_RGMII2_RXC is routed to the expansion connector at EXP_CONN_MUX6. X_LCD1_RESET is not connected to the expansion connector.
J15	1+2, 3+4 (Default)	X_RGMII2_TXD0 is routed to the ETH2 phy. X_X_I2C1_SCL is routed to the expansion connector at EXP_CONN_MUX7.
	2+3	X_RGMII2_TXD0 is routed to the expansion connector at EXP_CONN_MUX7. X_I2C1_SCL is not connected to the expansion connector.
J16	1+2, 3+4 (Default)	X_RGMII2_TXD1 is routed to the ETH2 phy. X_I2C1_SDA is routed to the expansion connector at EXP_CONN_MUX8.
	2+3	X_RGMII2_TXD1 is routed to the expansion connector at EXP_CONN_MUX8. X_I2C1_SDA is not connected to the expansion connector.
J17	1+2, 3+4 (Default)	X_RGMII2_TXD2 is routed to the ETH2 phy. X_RGMII1_RX_CTL is routed to the expansion connector at EXP_CONN_MUX9.
	2+3	X_RGMII2_TXD2 is routed to the expansion connector at EXP_CONN_MUX9. X_RGMII1_RX_CTL is not connected to the expansion connector.
J18	1+2, 3+4 (Default)	X_RGMII2_TXD3 is routed to the ETH2 phy. X_RGMII1_RXC is routed to the expansion connector at EXP_CONN_MUX10.
	2+3	X_RGMII2_RXD3 is routed to the expansion connector at EXP_CONN_MUX10. X_RGMII1_RXC is not connected to the expansion connector.
J19	1+2, 3+4 (Default)	X_RGMII2_TX_CTL is routed to the ETH2 phy. X_RGMII1_TX_CTL is routed to the expansion connector at EXP_CONN_MUX11.
	2+3	X_RGMII2_TX_CTL is routed to the expansion connector at EXP_CONN_MUX11. X_RGMII1_TX_CTL is not connected to the expansion connector.
J20	1+2, 3+4 (Default)	X_RGMII2_TXC is routed to the ETH2 phy. X_RGMII1_TXC is routed to the expansion connector at EXP_CONN_MUX12.
	2+3	X_RGMII2_TXC is routed to the expansion connector at EXP_CONN_MUX12. X_RGMII1_TXC is not connected to the expansion connector.

RGMII requirements should be considered when interfacing with RGMII2 via the expansion connector. It is recommended to verify all of the necessary timing budget parameters, such as trace length matching and skew/delay between clock and data, will meet the RGMII timing specifications.