96Boards Carbon

Overview

The 96Boards is based on the STMicroelectronics STM32F401RET Cortex-M4 CPU and also contains a nRF51822 chip connected over SPI for BLE connectivity.

The 96Boards Carbon board is built with two chips: an STMicroelectronics STM32F401RET Cortex-M4 CPU and an nRF51822 chip connected to the Cortex-M4 CPU over SPI for Bluetooth LE connectivity. Even though both chips exist on the same physical board, they must be programmed separately:

  • The 96b_carbon/stm32f401xe configuration is used when developing programs for the main chip on the board, the STM32F401RET. Users will likely want to write applications targeting this chip, using the 96b_carbon configuration, since it is connected to all of the breakout I/O headers.

  • The 96b_carbon/nrf51822 configuration should be used for programming the secondary nRF51822 chip. Most users will likely not develop applications for this chip, since Zephyr already provides a sample application that can be flashed onto the nRF51822 to provide Bluetooth functionality to applications on the main STM32F401RET chip.

For instructions on how to set up the nRF51822 to develop Bluetooth applications, see Providing Bluetooth to 96b_carbon.

After you have flashed your nRF51, you can perform basic validation of this Bluetooth setup using the instructions below.

96Boards Carbon

96Boards Carbon

Hardware

96Boards Carbon provides the following hardware components:

  • STM32F401RET6 in LQFP64 package

  • ARM® 32-bit Cortex®-M4 CPU with FPU

  • 84 MHz max CPU frequency

  • VDD from 1.7 V to 3.6 V

  • 512 KB Flash

  • 96 KB SRAM

  • GPIO with external interrupt capability

  • 12-bit ADC with 16 channels

  • RTC

  • Advanced-control Timer

  • General Purpose Timers (7)

  • Watchdog Timers (2)

  • USART/UART (4)

  • I2C (3)

  • SPI (3)

  • SDIO

  • USB 2.0 OTG FS

  • DMA Controller

  • Bluetooth LE over SPI, provided by nRF51822

More information about STM32F401RE can be found here:

Supported Features

The Zephyr 96b_carbon/stm32f401xe board configuration supports the following hardware features:

Interface

Controller

Driver/Component

NVIC

on-chip

nested vector interrupt controller

SYSTICK

on-chip

system clock

UART

on-chip

serial port

GPIO

on-chip

gpio

PINMUX

on-chip

pinmux

FLASH

on-chip

flash

SPI

on-chip

spi

I2C

on-chip

i2c

USB OTG FS

on-chip

USB device

More details about the board can be found at 96Boards website.

The default configuration can be found in boards/96boards/carbon/96b_carbon_stm32f401xe_defconfig

Connections and IOs

LED

  • LED1 / User1 LED = PD2

  • LED2 / User2 LED = PA15

  • LED3 / BT LED = PB5

  • LED4 / Power LED = VCC

Push buttons

  • BUTTON = BOOT0 (SW1)

  • BUTTON = RST

External Connectors

Low Speed Header

PIN #

Signal Name

STM32F401 Functions

1

UART2_CTS

PA0

3

UART2_TX

PA2

5

UART2_RX

PA3

7

UART2_RTS

PA1

9

GND

GND

11

USB5V

USB5V

13

AIN12

PC2

15

AIN14

PC4

17

UART6_TX

PC6

19

GPIO

PC8

21

I2C1_SCL

PB6

23

I2C1_SCA

PB7

25

I2C2_SCA

PB3

27

I2C2_SCL

PB10

29

RST_BTN

RST_BTN

PIN #

Signal Name

STM32F401 Functions

2

SPI2_SS

PB12

4

SPI2_MOSI

PB15

6

SPI2_MISO

PB14

8

SPI2_SCK

PB13

10

GND

GND

12

VCC2

VCC2

14

AIN13

PC3

16

AIN15

PC5

18

UART6_RX

PC7

20

GPIO

PC9

22

I2C1_SCL

PB8

24

I2C1_SDA

PB9

26

AIN10

PC0

28

AIN11

PC1

30

NC

NC

More detailed information about the connectors can be found in 96Boards IE Specification.

External Clock Sources

STM32F4 has two external oscillators. The frequency of the slow clock is 32.768 kHz. The frequency of the main clock is 16 MHz.

Serial Port

96Boards Carbon board has up to 4 U(S)ARTs. The Zephyr console output is assigned to USART1. Default settings are 115200 8N1.

I2C

96Boards Carbon board has up to 2 I2Cs. The default I2C mapping for Zephyr is:

  • I2C1_SCL : PB6

  • I2C1_SDA : PB7

  • I2C2_SCL : PB10

  • I2C2_SDA : PB3

SPI

96Boards Carbon board has up to 2 SPIs. SPI1 is used for Bluetooth communication over HCI. The default SPI mapping for Zephyr is:

  • SPI1_NSS : PA4

  • SPI1_SCK : PA5

  • SPI1_MISO : PA6

  • SPI1_MOSI : PA7

  • SPI2_NSS : PB12

  • SPI2_SCK : PB13

  • SPI2_MISO : PB14

  • SPI2_MOSI : PB15

USB

96Boards Carbon board has a USB OTG dual-role device (DRD) controller that supports both device and host functions through its mini “OTG” USB connector. Only USB device functions are supported in Zephyr at the moment.

  • USB_DM : PA11

  • USB_DP : PA12

Programming and Debugging

There are 2 main entry points for flashing STM32F4X SoCs, one using the ROM bootloader, and another by using the SWD debug port (which requires additional hardware). Flashing using the ROM bootloader requires a special activation pattern, which can be triggered by using the BOOT0 pin. The ROM bootloader supports flashing via USB (DFU), UART, I2C and SPI. You can read more about how to enable and use the ROM bootloader by checking the application note AN2606, page 109.

Flashing

Installing dfu-util

It is recommended to use at least v0.8 of dfu-util. The package available in debian/ubuntu can be quite old, so you might have to build dfu-util from source.

Flashing an Application to 96Boards Carbon

Connect the micro-USB cable to the USB OTG Carbon port and to your computer. The board should power ON. Force the board into DFU mode by keeping the BOOT0 switch pressed while pressing and releasing the RST switch.

Confirm that the board is in DFU mode:

$ sudo dfu-util -l
dfu-util 0.8
Copyright 2005-2009 Weston Schmidt, Harald Welte and OpenMoko Inc.
Copyright 2010-2014 Tormod Volden and Stefan Schmidt
This program is Free Software and has ABSOLUTELY NO WARRANTY
Please report bugs to dfu-util@lists.gnumonks.org
Found DFU: [0483:df11] ver=2200, devnum=15, cfg=1, intf=0, alt=3, name="@Device Feature/0xFFFF0000/01*004 e", serial="3574364C3034"
Found DFU: [0483:df11] ver=2200, devnum=15, cfg=1, intf=0, alt=2, name="@OTP Memory /0x1FFF7800/01*512 e,01*016 e", serial="3574364C3034"
Found DFU: [0483:df11] ver=2200, devnum=15, cfg=1, intf=0, alt=1, name="@Option Bytes /0x1FFFC000/01*016 e", serial="3574364C3034"
Found DFU: [0483:df11] ver=2200, devnum=15, cfg=1, intf=0, alt=0, name="@Internal Flash /0x08000000/04*016Kg,01*064Kg,03*128Kg", serial="3574364C3034"
Found Runtime: [05ac:8290] ver=0104, devnum=2, cfg=1, intf=5, alt=0, name="UNKNOWN", serial="UNKNOWN"

You should see following confirmation on your Linux host:

$ dmesg
usb 1-2.1: new full-speed USB device number 14 using xhci_hcd
usb 1-2.1: New USB device found, idVendor=0483, idProduct=df11
usb 1-2.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 1-2.1: Product: STM32 BOOTLOADER
usb 1-2.1: Manufacturer: STMicroelectronics
usb 1-2.1: SerialNumber: 3574364C3034

Then build and flash an application. Here is an example for the Hello World application.

# From the root of the zephyr repository
west build -b 96b_carbon/stm32f401xe samples/hello_world
west flash

Connect the micro-USB cable to the USB UART (FTDI) port and to your computer. Run your favorite terminal program to listen for output.

$ minicom -D <tty_device> -b 115200

Replace <tty_device> with the port where the board 96Boards Carbon can be found. For example, under Linux, /dev/ttyUSB0. The -b option sets baud rate ignoring the value from config.

Press the Reset button and you should see the following message in your terminal:

Hello World! arm

Verifying Bluetooth Functionality

This section contains instructions for verifying basic Bluetooth functionality on the board. For help on Zephyr applications in general, see Building an Application.

  1. Flash the nRF51 with the hci_spi sample application as described in Providing Bluetooth to 96b_carbon.

  2. Install the dfu-util flashing app, as described above.

  3. Build and flash the samples/bluetooth/peripheral_hr application for 96b_carbon. See the instructions above for how to put your board into DFU mode if you haven’t done this before:

    # From the root of the zephyr repository
west build -b 96b_carbon/stm32f401xe samples/bluetooth/peripheral_hr
west flash

  4. Refer to the instructions in Heart-rate Monitor (Peripheral) for how to verify functionality.

Congratulations! Your 96Boards Carbon now has Bluetooth connectivity. Refer to Bluetooth for additional information on further Bluetooth application development.

Debugging

The 96b_carbon/stm32f401xe board can be debugged by installing a 100 mil (0.1 inch) header into the header at the bottom right hand side of the board, and attaching an SWD debugger to the 3V3 (3.3V), GND, CLK, DIO, and RST pins on that header. Then apply power to the 96Boards Carbon via one of its USB connectors. You can now attach your debugger to the STM32F401RET using an SWD scan.