TMS320F280049C: Physical layer hardware conditions for FSI communication between two MCUs

Hello,

You shouldn't have any issues communicating via single-ended connections for that speed. Any additional hardware (like a differential converter) would just be used to reduce noise on the signal, which is usually only necessary for higher speeds or long-distance communication. I would recommend you try out some of the FSI examples in C2000ware using the DuPont cables and see if you get any errors. If so, that would indicate that there is too much noise on the line for the FSI receiver to interpret the data properly. 

Best Regards,

Delaney

Hello,

Thank you  for your answers.

I have some confusion about the FSI example 16(fsi_ex_daisy_handshake_lead/node).

Is the TMDSFSIADAPEVM FSI Adapter Board necessary for low speed communication (1MHz) using FSI ex16 between two LaunchPads (LAUNCHXL-F280049C )?

Or is it possible to achieve FSI low-speed communication between two LaunchPads via FSI ex16 using only DuPont cable?

Best Regards,

Wye

Hi Wye,

WY Z said:

Or is it possible to achieve FSI low-speed communication between two LaunchPads via FSI ex16 using only DuPont cable?

Yes, this is possible. You would just need to connect the pins directly using DuPont cables as mentioned in the example:

If you are referring to how the Using the Fast Serial Interface (FSI) With Multiple Devices in an Application application note uses FSI example 16 and two of the EVM's for the connection, this is just to show how they could be used to reduce noise on the line. It is possible for the example to work without EVMs as well.

I believe in your case the 1 MHz speed will work fine with single-ended connections, however if you have any issues when running the examples that would indicate an error, you can scope the pins and see if there is a large amount of noise. The F28004x GPIOs simply need to recognize a low voltage as logical low and a high voltage as logical high, so as long as any noise is not interfering with that logic, FSI communication will work fine. You can see the device datasheet to find what voltage is considered logical high (VIH) and what voltage is considered logical low (VIL). However, like I said before, this shouldn't be necessary since I don't foresee you having any noise issues with that speed.

Best Regards,

Delaney

Hi Delaney,

I'm experiencing communication failures in using the FSI ex16 to communicate through two LaunchPads at 5MHz.

Whether DMA is used (software triggered) or DMA mode is not enabled, the register TX_EVT_STS.FRAME_DONE is set to 1 after running the programme on the LEAD side.

But none of the NODE side receives data.The corresponding status bits of the RX_EVT_STS registers were not changed.

No signals are detected by the logic analyser on the corresponding receive and transmit pins of the LEAD and NODE LaunchPads.

Is it necessary to make additional settings in the ex16 programme to ensure successful communication?

Best Regards,

Wye

Hi Wye,

If there is no FSI signal showing up on the FSITX_TX0 pin of the lead node but the TX_EVT_STS.FRAME_DONE is set, then this seems like a GPIO issue. Can you verify that you are using the following launchPAD pin connections (same for both lead & node devices):

FSITX CLK - GPIO 27

FSITX D0 - GPIO 26

FSITX D1 - GPIO 25

FSIRX CLK - GPIO 13

FSIRX D0 - GPIO 12

FSIRX D1 - GPIO 11

Just to clarify, have you made any modifications at all to the example?

Best Regards,

Delaney