TMS320F28388D: Expanding RAM on the CM core and intended use of Ethernet communication

Danilo A.

Mastermind 34720 points

Part Number: TMS320F28388D

Hi Team,

Posting on behalf of our customer.

I will share this E2E post to our customer so he can reply when needed.

We are contacting you as we are utilising your F28388D MCU for our development.

When it comes to this MCU, our understanding is the following:

The C28 CPU1 and CPU2 cores are intended to be used as Real-Time compliant "heavy-lifters", i.e. to process any data that is coming through from the CM
The CM is intended as the "interface with the outside world", as it is the only core that can directly access and use communication interfaces such as Ethernet, EtherCAT, etc.

You have repeatedly stated on your forums that, as of 2025 and now 2026, TI only supports the use of FreeRTOS as the operating system, and lwIP as the TCP/IP stack. Your examples confirm this, with the lwIP example directly compiled for the CM subsystem.

Here lies our problem: the CM subsystem only supports 96KB of usable RAM. FreeRTOS + lwIP on their own take up a considerable portion of this RAM, and there is barely any left over to run application code. Now, while the C28 subsystems support an EMIF to allow expansion of the on-board RAM, the CM subsystem apparently does not.

Is this all correct so far? If so, given that the CM core is the only one that can access the Ethernet peripheral and must use FreeRTOS+lwIP to do so, what is the intended design to make this work with the very small onboard memory? We can currently spin up a few threads and open a few UDP/TCP sockets before we run into FaultISR errors due to insufficient memory.

Regards,

Danilo

9 months ago

0 Alex Tanapon Leonardi 9 months ago

Prodigy 30 points

Thank you for posting this on our behalf. We look forward to any assistance on the matter.

0 AndyP 9 months ago

Expert 1806 points

Hi Danilo,

you have here a VERY valid point. The CM RAM is disappointingly small, we even had to use the memory of unused peripherals to make it work, and of course no RTOS at all to begin with.
Years of not fixed ethernet driver bugs (still there!), we had to patch it by ourselves.
It is even more disappointing and really incomprehensible that the new chips with the C29 core don't have Ethernet at all, and there are no plans to make one! So we don't have a straight upgrade path at all.
Very, very disappointing!

Best regards,
Andy

0 Alex Tanapon Leonardi 9 months ago

Prodigy 30 points

Thank you for your comment on the matter AndyP .

Could a Texas representative please give us some assistance on the matter? Specifically, we need to run the CM subsystem with FreeRTOS (as suggested by you, due to TI-RTOS no longer being supported) and our software is written in C++. How do you suggest we proceed in running the OS, lwIP, the other peripherals that the CM system handles, and also some minimal application code, all within the limited and non-expandable RAM that is provided?

Thank you for your help.

0 Gouri Siva M 8 months ago in reply to Alex Tanapon Leonardi

TI__Intellectual 840 points

Hi ,

You can refer the examples provided in the latest SDK for freertos + lwip support.

Due to memory constraints we cannot add socket APIs.

0 Alex Tanapon Leonardi 8 months ago in reply to Gouri Siva M

Prodigy 30 points

Hello and thank you for the input,

we have already seen the examples. They sadly do not help with the specificities I have outlined above.

0 Gouri Siva M 8 months ago in reply to Alex Tanapon Leonardi

TI__Intellectual 840 points

Hi,

We are limited to have only 96KB RAM so we cannot expand from this.

C2000™︎ microcontrollers

C2000 microcontrollers forum

TMS320F28388D: Expanding RAM on the CM core and intended use of Ethernet communication