AWR6843ISK: How to Calculate SPI Throughput

vishnu vikash

Part Number: IWR6843ISK
Other Parts Discussed in Thread: IWR6843, AWR6843

Dear sir/madam

I am planning to transfer partial 2D FFT output from IWR6843 to TDA3x via SPI. In the current case, IWR6843 is master and its SPI clock is 40MHz.

SPI protocol - 4 Wire (SCLK, MOSI, MISO ,CS)

Word length - 32 bit with header

6843 clock - 40 Mhz (25ns cycle)

Please let me know how to calculate the maximum possible throughput that can be achieved via SPI by considering R4 CPU overhead.

Thanks & Regards

Vishnu

over 3 years ago

0 Vaibhav Mahimkar over 3 years ago

TI__Mastermind 23725 points

Hello

Can you please help us understand more about this application based on the final use case.

Please see personal messages.

Thank you,

Vaibhav

0 vishnu vikash over 3 years ago in reply to Vaibhav Mahimkar

Intellectual 355 points

Dear Vaibhav

Application is Automotive and Non-Adas.

Please let me know how to calculate the maximum possible SPI throughput. So that It will be helpful for me to determine the partial 2DFFT size and frame rate for my application.

Thanks & Regards

Vishnu

0 Sudharshan KN over 3 years ago in reply to vishnu vikash

TI__Genius 10550 points

Hi,

We have tried to use the SPI interface with 32MHz clock. and with this we can go up to 16kBps. The tests were done by sending repeated data (mainly synthetic data with just the TLV header and some fixed values in bytes) from the device. The data was sent at different rates to mimic the traffic on SPI lines.

Regards,

Sudharshan K N

0 vishnu vikash over 3 years ago in reply to Sudharshan KN

Intellectual 355 points

HI,

1. How can we get 16KBps for a 32MHz clock?

2. Can you please explain to me the speed calculation of the SPI interface?

3. In AWR6843 ISK, what is the maximum SPI clock possible to achieve?

Thanks & Regards

Vishnu

0 Sudharshan KN over 3 years ago in reply to vishnu vikash

TI__Genius 10550 points

Hi,

#1 - 16kBps is the max that we have tried at our end. We may need to see what is the max speed possible. BTW do you have any requirement from your side based on the requirement?

#2 - Please elaborate on the same.

#3 - As per the specs we should be able to use 40MHz.

Regards,

Sudharshan K N

0 vishnu vikash over 3 years ago in reply to Sudharshan KN

Intellectual 355 points

Hi,

My understanding is 1 bit of data is transferred for the very SPI clock. By setting SPI clock speed as 40 MHz. Ideally, it should be possible to transfer 40mbps. Let's say by considering CPU latency and SPI header overhead, let's assume throughput comes down to 50%. In that case, it should be possible to transfer 5MBps at least.

But you are saying it is possible to transfer 16KBps through SPI? My requirement is to transfer 256KB of data in 100ms via SPI. Please clarify whether it is possible to achieve it or not?

Thanks & Regards

Vishnu

0 Sudharshan KN over 3 years ago in reply to vishnu vikash

TI__Genius 10550 points

sorry for the typo all way along. it is 16MBps and not kbps. The requirement you have mentioned should be possible.

0 vishnu vikash over 3 years ago in reply to Sudharshan KN

Intellectual 355 points

Can you please explain to me how an SPI clock with 32MHz is able to transfer 16MBps data with all the overhead?

Thanks & Regards

Vishnu

0 Sudharshan KN over 3 years ago in reply to vishnu vikash

TI__Genius 10550 points

Hi,

the testing we have done is packet by packet basis. basically transmitting the TLV header from the MSS code and check if the same is received correcly on the other side. We haven't done continuous transmission use case. The throughput in continuous transmit case could be different.

Regards,

Sudharshan K N

0 vishnu vikash over 3 years ago in reply to Sudharshan KN

Intellectual 355 points

HI,

1. Can we please share with me the sample code you used to calculate the throughput? It will be helpful for me to have the same evaluation setup here.

2. How much difference in throughput we can expect in continuous mode?

Regards,

Vishnu

Sensors

Sensors forum

AWR6843ISK: How to Calculate SPI Throughput