TJA1128 wake up source reading

[atranzillo93]

I write about TJA1128 LIN mini system basis chip.

The model used is TJA1128A.

I'm trying to read wake up source via UART. The TJA is in the correct mode when reading, i.e. it is in PORT mode.

As soon as I generate a remote (LIN) or local (button) wake-up event, starting from a SLEEP condition, the TJA wakes up correctly but the chip response following the UART request is always the same (0xFC) .

I am attaching some pictures to explain better.

WAKE UP DA LIN

WAKE UP DA BUTTON

For completeness, I add that:

The TJA has been configured in the following ways:

• RSTN output reset pulse width 4ms
• Sleep mode enabled
• Remote wake up enabled
• Local wake up on WAKE1 on rising edge

The UART has been configured as follows:

• 1 stop bit
• 8 data transfer bits
• No parity
• LSB first
• Baud rate 19200bps (also tested with 9600bps but no success)

Can tou help me?

[TomasVaverka]

Hi Anna,

I do not see the signals of EN and STBN. Without these signals I cannot comment on above plots. Could you measure with EN, STBN, RXD, RXD, RSTN and wake source pin (LIN or WAKE)?

Best regards,

Tomas

[atranzillo93 · Accepted solution]

[solved]

Hi Tom, 

I specify that I had already checked the EN and STB pins on the oscillo but I had triggered on the transition event in PORT mode. By setting the oscillo in roll mode, I noticed that at power ON, due to a configuration error, the EN pin was set HIGH for a certain time, most likely generating a transition of chip in NORMAL mode. Consequently, the transition to PORT mode had no effect (EN = HIGH and STB = HIGH). That's why the chip always responded with the same byte.

Now, it works.

LOCAL WAKE UP

REMOTE WAKE UP

[atranzillo93]

Hi,

I followed the software flow because I had already read the application note.

Can you help me?

Anna

[TomasVaverka]

Hi,

Please take a closer look at Chapter 7.5 Wake-up source recognition and recommended Software Flow in Chapter 10 of the TJA1128 Application Hints:

https://www.nxp.com/products/interfaces/automotive-lin-solutions/lin-mini-system-basis-chip:TJA1128

Best regards,

Tomas