Part Number:OMAP-L138
Tool/software: TI-RTOS
Hello,
we want to use a serial port on the OMAP-L138 as a second network (Layer 2) interface to expand the Ethernet network over a low-bandwidth serial link. Due to low cable bandwidth we cannot use plain Ethernet over this specific link, and we dont want to use PPP because that would be Layer 3 and then we would have a different IP subnet and the OMAP would have to act as a router and we dont want that.
So reading into the NDK documentation I saw that there is a Serial mini-driver and it looks like it could be used to create a virtual ethernet-like interface over a serial port (possible with HDLC), which we would like to be bridged (at Layer 2 - act as a switch) with the physical Ethernet interface. So, I have the following questions:
- Is it really possible to create a Layer-2 network interface over a serial port using the serial mini-driver?
- Can the NDK create a bridge between two network interface, acting as an ethernet switch? Even acting as an old-style ethernet hub could be a viable option.
- Does the NDK on the OMAP-L138 apply flow control (Pause frames) on the Ethernet when acting as a switch? This will definitely be needed because the serial link will be much slower than the Ethernet and any burst coming in from the Ethernet side will need to be regulated to avoid packet loss.
Our plan B is to use a separate microcontroller (eg. TM4C129) connected to another switch port that will be dedicated to transferring Ethernet frames between the physical EMAC interface and a serial port (with some form of framing, eg. HDLC). This seems easier to do, either with TIRTOS+NDK, or with bare metal code, and have Pause frames being sent when the UART TX queue is full, but we would like to avoid the extra hardware.
Any help appreciated,
Giannis