Author:
Nico Korn
Project:
RNDIS for ST HAL library
Used target:
Blackpill board with stm32f411
Usage:
To have platform independent network interfaces over usb which is working with Linux, Windows, Mac OS ect.
Description:
Remote NDIS (RNDIS) is a bus-independent class specification for Ethernet (802.3) network devices on dynamic Plug and Play (PnP) buses such as USB, 1394, Bluetooth, and InfiniBand. Remote NDIS defines a bus-independent message protocol between a host computer and a Remote NDIS device over abstract control and data channels. Remote NDIS is precise enough to allow vendor-independent class driver support for Remote NDIS devices on the host computer.
This rndis project is based on the HAL library and uses FreeRTOS. The rndis usb interface is functional and implemented. At least enummeration is working if you flash this project on a stm32f411 based board with usb socket.
The rs485 interface is just a template for a second interface and needs to be completed. You could also implement a webserver, a dhcp server and a dns which are using the second interface.
For frame management I implemented a ringbuffer "queuex". The ringbuffers parameters can be found in its header file. I'm using staticly allocated memory for better performance. Each interface has its own ringbuffer, so they don't block each other.
I tried also a linked list with heap allocation, but that apporach was less performand due to memory allocation during runtime but memory wise it was more efficient.
Data handling on the rndis usb interface is zero copy -> As soon as a complete frame has been received the head will jump to the next ringbuffer slot (if it is not occupied by the tail of course).
There is only one task running the queuex manager of both interfaces, not using any FreeRTOS features like task bocking with notifiers. So you could also just copy the task content into a baremetall main and let it run without FreeRTOS.
It should be easy to port the library to other st mcu's. Generate a new cdc usb project with cubemx and replace the usb relevant rndis files with the ones from this project.
Info:
The rndis library is based on the library from Sergey Fetisov: https://github.com/fetisov/lrndis and is using a rndis protocol library from Colin O'Flynn. Many thanks for your efforts! For more general information about RNDIS visit: https://docs.microsoft.com/de-de/windows-hardware/drivers/network/overview
Versions:
STM32_HAL_RNDIS 0.2.0.0
FreeRTOS Kernel V10.3.1
STM32Cube_FW_F4_V1.26.0
STM32CubeMX 6.3.0