DRA829_Uart_To_Lin ----Break field generation and Break field detection

user5060116

Other Parts Discussed in Thread: DRA829

I am developing LIN based on Uart on DRA829,But i cannot generate break field(13 bit Low),and Can not detect break field (13 bit low). Please help me

1:break field generate:I found break condition in TM(A break condition is activated by setting the UART_LCR[6] BREAK_EN bit),but i do not know how to Control the length(13 bit low) of the break field

2:break field detection:UART_LSR_UART[4]RX_BI indicates a break detection,but the length is one character + 1bit time,not 13 bit,how can i do to detect 13_bit Low break field?

over 5 years ago

0 Karan Saxena over 5 years ago

TI__Guru* 77754 points

Hi,

Have you looked at the already existing diagnostic test for LIN in the SDK?

You can find the source code at psdk_rtos_auto_j7_07_00_00_11/pdk_jacinto_07_00_00/packages/ti/board/diag/lin - this implements LIN over UART.

Regards,

Karan

0 user5060116 over 5 years ago in reply to Karan Saxena

Prodigy 180 points

thanks for your help!

I Found diagnostic test for Lin in SDK,and read the code,but i don not understand how it handle the Break Field.It seems that two bytes(one is 0x00,the other is 0x20) is transmitted.But there will be a stop bit(high) after 0x00 is transmitted,it can not be a solid break field(13 bit low).Can you please enlight me about this?

0 Karan Saxena over 5 years ago in reply to user5060116

TI__Guru* 77754 points

Hi,

Let me check with the owner of the diagnostic test.

Regards,

Karan

0 user5060116 over 5 years ago in reply to Karan Saxena

Prodigy 180 points

Hi,

do you have any reply from the ower?

0 Karan Saxena over 5 years ago in reply to user5060116

TI__Guru* 77754 points

Hi,

I will update ASAP.

Regards,

Karan

0 M V Pratap Reddy over 5 years ago in reply to Karan Saxena

TI__Intellectual 1160 points

Hi,

Break generation and detection by LCR and LSR registers is specific to UART protocol. You will not be able to control the break field generation for LIN specification using these registers.

Minimum 14 bits (13 dominant + 1 delimiter) is the requirement for break field in LIN frame. But it can be extended upto 20 bits. You need to form your message to fill the data with exact bit numbers based on the break field size you decide to use. You can use a structure with bit fields to form your frame.

In case of diagnostic test we use two bytes for break field though we send only 14 bits. Since the communication is between two nodes within the EVM for HW data path verification, there is a liberty of controlling which fields of frame can be parsed and which can be ignored. In case of nodes in active LIN network you can form the frame as I mentioned above.

- Pratap.

0 user5060116 over 5 years ago in reply to M V Pratap Reddy

Prodigy 180 points

HI,

I can form my message to fill the data with 13 bit low for lin break field ,But Uart can not transmit so much Bit once(at most 8 bit).how shoud l handle this?

besides,How can i detect the Break Field for LIN slave node?

0 user5060116 over 5 years ago in reply to user5060116

Prodigy 180 points

Hi,

Looking forward to your reply!

0 user5060116 over 5 years ago in reply to Karan Saxena

Prodigy 180 points

Hi,

I am still confused about Lin break generation and detection,Please help me out!

0 M V Pratap Reddy over 5 years ago in reply to user5060116

TI__Intellectual 1160 points

Hi,

For sending the break field without any additional bits in between over UART, typical method is to decrease the baudrate on Tx side by 2/3 times and send a zero byte. Because of the data rate mismatch receiver sees more number of 0 bits which matches with the break condition.

If all the LIN nodes in the network are controlled by your software, you should be able to use UART break generation and detection feature to generate a break on master and detect it on slave. But this may not work if there are LIN nodes which expects exact break field as per the spec.

- Pratap.

Interface

Interface forum

DRA829_Uart_To_Lin ----Break field generation and Break field detection