TMS570LS1224: Confusion about length of transmitting data

Datïan

Hi,

I'm testing RS485 in my board with Launchpad TMS570LS12x. It can receive and transmit data. What data it received is exactly as what I send by console application in my PC. But the length of data it transmitted is always less 2 than my expectation. Please help me to find out something wrong or what I missed.

The declaration of TSIZE1 and TEXT1 are as below.

The code of transmitting is as below.

I defined TSIZE as 14, 15 and 16 to test. The respective results showed the actual length of data received in PC are 12, 13 and 14, as below.

Best Regards

Datïan

over 6 years ago

0 QJ Wang over 6 years ago

TI__Guru**** 200526 points

Hello Datian,

The code you posted looks fine. Did you probe the SCI TX bus to check if the data is transmitted?

0 Datïan over 6 years ago in reply to QJ Wang

Expert 1295 points

Hello QJ,

I did not probe the SCI TX bus. I just use console application to show the received data. Do you suspect the two bytes might be eaten by PC ?

Kind Regards

Datïan

0 QJ Wang over 6 years ago in reply to Datïan

TI__Guru**** 200526 points

Hello Datian,

This is why I asked you to probe the data on SCI TX bus.

0 Datïan over 6 years ago in reply to QJ Wang

Expert 1295 points

Hello QJ,

I'll probe it. I don't understand why the result of testing on RS485 is much better than RS232.

Warm Regards

Datïan

0 Datïan over 6 years ago in reply to QJ Wang

Expert 1295 points

Hello QJ,

Many thanks for your suggestion of probing the data on SCI TX bus. The idle of TX is not unexpective. I found the cause is enabling RE to fast after sciSend.

The receiving data by PC application is exactly as what I expect after I add a delay between sciSend and enabling RE, as below.

However what confused me is the behaviour of transmitting in poll mode. I always believe sciSend in poll mode will not return until finishing transmitting every byte. Is my cognition about poll mode not correct ?

Kind Regards

Datïan

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TMS570LS1224: Confusion about length of transmitting data