Customer board won't boot at all - no output on UART 3

Tiemen Spits

Other Parts Discussed in Thread: AM3505

I ran into the following issue in recent weeks and think it is worth sharing:

The customer received his own board back and it will not boot at all. All signals from the TPS65xxx look good, sysclk is good, yet there is no output at all from the UART. When I hook up my JTAG and use CCS, I can load the programs in DDR and everything boots just fine. Yet when I don't use JTAG, the board never boots - what is going on?

over 15 years ago

0 Tiemen Spits over 15 years ago

TI__Intellectual 1110 points

While debugging using CCS and JTAG we found nothing out of the ordinary, so we went back to the schematics and noticed that the customer was not using EMU0/1 for the JTAG but had planned the alternate pin mux (GPIOs) for certain functions and strapped them externally accordingly. As the result, the EMU0/1 pins were coming up in a 0/1 configuration.

According to a note in the AM3505/17 top func documentation - under these conditions, the ARM WILL BE HELD IN RESET !! This information is currently not available in the OMAP35xx /37xxTRM or DM; an update request has been submitted.

Exerpt of the shiva_top_func.doc Debug Support Chapter:

EMU1	EMU0	Effect	Comments
0	0	Boundary scan Stacked die	Only for D2D, to include the same for boundary scan
0	1	TCK direct	Free run, application will boot as soon as POR is released.
1	0	WaitInReset (WIR)	Arm will be under reset until released from debugger.
1	1		Free run, application will boot as soon as POR is released.

Of course using CCS with JTAG would get the ARM out of reset and everything would work normally as we would pull the ARM out of reset manually.

Changing the HW strapping of EMU0/1 to a 1/1 configuration solved the issue.

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Customer board won't boot at all - no output on UART 3