We took the core of the IPC-CPUF407 modular computer and placed it on a board with Rasberry PI format. The result is probably the most sophisticated module with an STM32F407 processor that includes Fast Ethernet and Wi-Fi communication interfaces, a MicroSD card slot, two USB interfaces, a GPIO expansion connector with digital and analog inputs and outputs, and a serial terminal with a command line with USB-C bridge.
At the heart is a 168 MHz ARM Cortex-M4 processor with 1MB of flash and 192 kB of RAM. The Ethernet PHY is connected via an RMII interface and allows for 100 Mbit/s speed. Unique is the Wi-Fi transceiver connection solution, which is implemented via a fast SDIO interface, compared to other modules that always use a slower SPI modem with an integrated TCP/IP stack. Hence, the transmission of packets is directly in raw form and the TCP/IP stack is implemented in the same way as with Ethernet using LwIP. Ethernet and Wi-Fi thus behave as identical interfaces from a system network perspective, with the possibility of custom implementation of higher-level functions and protocols (TCP, UDP, NTP, HTTP, ...). The antenna for Wi-Fi is connected externally via an SMA connector, so it guarantees better reception than the integrated antenna on the PCB.
Since the STM32F407 has only one SDIO interface, this interface is switched between the Wi-Fi module and the SD card. This is a unique solution that, as far as we know, is not used on any other module. The microSD card can thus serve as a high-capacity medium for storing sensor data, etc.
Other features are also above standard. The module contains two USB 2.0 interfaces, one at full 480 Mbit/s, where the USB is implemented by a tranceiver with ULPI interface. This makes it suitable for e.g. connecting USB drives as additional storage. The second USB port uses the integrated USB PHY in the processor and has a slower speed of 12 Mbit/s. This is suitable e.g. for connecting sensors and other peripherals.
The module can be equipped with a backup battery for RTC or to save the module status in case of power failure.
The 5V power supply is connected either via the USB-C connector, which also has a command line terminal, or via the optional terminal block connector. It is then possible to separate the power supply from the USB-C terminal connection with a cable.
The advantage of the module is its low power consumption, in full operation it averages around 1W (200 mA) without connected peripherals.
The GPIO expansion connector has the same wiring as on the Rasberry PI, so most HAT expansion modules can be connected. INBROLLY is also preparing its own expansion modules.
The PI-CPUF407 will be on sale from September, price to be specified.