RTL8721F EVB

Tags: chip:rtl8721f arch:arm vendor:realtek

Realtek RTL8721F EVB development board

The RTL8721F EVB development board.

The RTL8721F EVB is a Realtek RTL8721F evaluation board. NuttX runs on the KM4TZ application core — an Arm Cortex-M55-compatible core running at up to 320 MHz. See the RTL8721F chip documentation for the full SoC specifications and the vendor-SDK dependency.

Features

  • RTL8721F: Arm Cortex-M55-compatible KM4TZ core up to 320 MHz, 512 KB SRAM, 4 MB NOR flash

  • Wi-Fi 6 (802.11 a/b/g/n/ax), dual-band 2.4/5 GHz station and SoftAP

  • SPI NOR flash (XIP)

  • LOG-UART console

Supported in this NuttX port:

  • NSH shell over the LOG-UART console

  • littlefs persistent storage mounted at /data (a dedicated SPI NOR flash partition)

  • Wi-Fi station and SoftAP through the wapi tool

  • DHCP client (STA) and DHCP server (SoftAP)

  • GPIO pins exposed as /dev/gpioN character devices (input, output and interrupt), driven directly on the SDK fwlib register layer

  • General-purpose UARTs exposed as /dev/ttySN serial devices, driven directly on the SDK fwlib register layer

  • I2C master buses exposed as /dev/i2cN character devices, driven directly on the SDK fwlib register layer

  • SPI master buses exposed as /dev/spiN character devices, driven directly on the SDK fwlib register layer

  • PWM output exposed as a /dev/pwm0 character device, driven directly on the SDK fwlib timer register layer

Buttons and LEDs

This NuttX port does not wire any user buttons or LEDs.

Configurations

Build and flash any of these per the RTL8721F build instructions; for the CMake build, source . tools/ameba/env.sh rtl8721f_evb first (the make build needs no sourcing).

$ ./tools/configure.sh rtl8721f_evb:<config-name>

gpio

Minimal NSH with the GPIO driver and the gpio example enabled (no Wi-Fi). The board registers three pins from its pin table (see boards/arm/rtl8721f/rtl8721f_evb/src/rtl8721f_gpio.c): an output at /dev/gpio0, an input at /dev/gpio1 and an interrupt pin at /dev/gpio2. Edit that table to match a board’s wiring. Exercise them with the example:

nsh> gpio -o 1 /dev/gpio0     # drive the output high
nsh> gpio /dev/gpio1          # read the input
nsh> gpio -w 1 /dev/gpio2     # wait for a falling-edge interrupt

Pins are encoded with the AMEBA_PA() / AMEBA_PB() helpers from arch/arm/src/common/ameba/ameba_gpio.h (port A/B, pin 0-31), matching the Ameba SDK PinName layout.

uart

Minimal NSH with the general-purpose UART driver and the serialrx / serialblaster examples enabled (no Wi-Fi). The LOG-UART owns the console and /dev/ttyS0, so the board registers UART0 from its table (see boards/arm/rtl8721f/rtl8721f_evb/src/rtl8721f_uart.c) as /dev/ttyS1 at 115200 8N1. Edit that table – controller, TX/RX pads and baud – to match a board’s wiring. The TX/RX pads use the same AMEBA_PA() / AMEBA_PB() encoding as the GPIO table; the driver muxes them to the UART function and pulls RX high through the SDK ROM. Exercise the port with the examples (loop TX back to RX, or wire it to a host serial adapter):

nsh> serialrx /dev/ttyS1 2600 &     # start the receiver first
nsh> serialblaster /dev/ttyS1 2600  # then loop TX back to RX

The line format can be changed at runtime through tcsetattr() (the config enables CONFIG_SERIAL_TERMIOS). UART3 is shared with Bluetooth and is not exposed by the driver.

i2c

Minimal NSH with the I2C master driver and the i2ctool (system/i2c) enabled (no Wi-Fi). The board registers its I2C controllers from a table (see boards/arm/rtl8721f/rtl8721f_evb/src/rtl8721f_i2c.c): I2C0 at /dev/i2c0 on PA22/PA23 and I2C1 at /dev/i2c1 on PA24/PA25. Edit that table – controller and SCL/SDA pads – to match a board’s wiring; the pads use the same AMEBA_PA() / AMEBA_PB() encoding as the GPIO table and are muxed to the I2C function through the SDK ROM. The I2C bus is open-drain, so fit external pull-ups on SCL/SDA. Probe a bus with the tool:

nsh> i2c dev -b 0 0x03 0x77     # scan /dev/i2c0 for devices

spi

Minimal NSH with the SPI master driver and the spi tool (system/spi) enabled (no Wi-Fi). The board registers two buses from its table (see boards/arm/rtl8721f/rtl8721f_evb/src/rtl8721f_spi.c): SPI0 at /dev/spi0 with CLK/MOSI/MISO on PA14/PA15/PA16 and a software chip-select on PA17, and SPI1 at /dev/spi1 with CLK/MOSI/MISO on PB13/PB14/PB15 and a software chip-select on PB16. Edit that table – controller, CLK/MOSI/MISO pads and CS pad – to match a board’s wiring; the pads use the same AMEBA_PA() / AMEBA_PB() encoding as the GPIO table and are muxed to the SPI function through the SDK ROM, while the chip-select is driven as a plain GPIO. Note that SPI0 and SPI1 route to different pad groups in the chip pin-mux spec (SPI0 on the PA group, SPI1 on the PB/PC group); pick pads the spec lists for that controller. Exercise a bus with the tool:

nsh> spi exch -b 0 -x 4 deadbeef     # full-duplex transfer on /dev/spi0
nsh> spi exch -b 1 -x 4 deadbeef     # full-duplex transfer on /dev/spi1

pwm

Minimal NSH with the PWM driver and the pwm example (examples/pwm) enabled (no Wi-Fi). The board registers one timer at /dev/pwm0 (see boards/arm/rtl8721f/rtl8721f_evb/src/rtl8721f_pwm.c): TIM4 drives up to four compare channels off one shared time base, so every channel shares one frequency and each carries its own duty cycle. The example table routes channel 1 to PA24 and channel 2 to PA25; edit it – one pad per channel, AMEBA_PWM_PIN_NC for the unused ones – to match a board’s wiring. The pads use the same AMEBA_PA() / AMEBA_PB() encoding as the GPIO table and are muxed to the PWM function through the crossbar. Set CONFIG_PWM_NCHANNELS to the number of channels used. Exercise it with the example:

nsh> pwm -d 25 -f 1000     # 1 kHz, 25% duty on /dev/pwm0

nsh

Networking-enabled NSH with littlefs at /data and the wapi Wi-Fi tool. The console is the LOG-UART at 1500000 8N1 (the rate is configured by the bootloader and inherited by NuttX). The Wi-Fi examples below are available from this configuration.

Wi-Fi

Station (connect to an AP):

nsh> wapi psk    wlan0 <password> 3
nsh> wapi essid  wlan0 <ssid> 1
nsh> renew wlan0

SoftAP (become an access point, with a DHCP server for clients):

nsh> wapi mode   wlan0 3
nsh> wapi psk    wlan0 <password> 3
nsh> wapi essid  wlan0 <ssid> 1
nsh> ifconfig    wlan0 192.168.4.1 netmask 255.255.255.0
nsh> dhcpd_start wlan0

Stop the SoftAP with wapi essid wlan0 <ssid> 0.

License Exceptions

This board depends on Realtek vendor code that is not part of NuttX and is subject to its own license:

  • The prebuilt Wi-Fi / Bluetooth firmware image and the Realtek ameba-rtos SDK libraries/headers linked into the image. See the SDK’s own license; the SDK is auto-fetched and is not redistributed in the NuttX tree.