the UART boot for AM3357

Huang Derek

Intellectual 360 points

Hi,

We got a problem about the UART boot.

We referred to the schematic offered by the TI,

and created our experimental circuit board.

when we chose the UART boot,

we found the TX of UART0 is always low,

and data that it sent is 0.(the correct data should be 43.)

could you give us suggestions for this problem?

over 12 years ago

0 Biser Gatchev-XID over 12 years ago

TI__Guru**** 393215 points

Hi Huang,

What schematic did you refer to? What do you have on your experimental board?

Best Regards

Biser

0 Huang Derek over 12 years ago in reply to Biser Gatchev-XID

Intellectual 360 points

Hi Biser,

the schematic that we got is this one (http://www.ti.com/litv/zip/sprr164).

please download it.

there are two UART ports, two Ethernet ports, two USB ports, one NAND flash and one DDR2 on our experimental board.

0 Biser Gatchev-XID over 12 years ago in reply to Huang Derek

TI__Guru**** 393215 points

Hi Huang,

Are you connecting to UART0 (AM335X pin E16 is TX from processor, pin E15 is RX to processor)? These are the pins that are used for UART boot.

Best Regards

Biser

0 Huang Derek over 12 years ago in reply to Biser Gatchev-XID

Intellectual 360 points

Hi Biser,

our UART0 consist of E16 and E15.

We have checked this one and

we know the UART is the debug port.

we do not know why TX is always low and

send 0 to PC consecutively.

0 Biser Gatchev-XID over 12 years ago in reply to Huang Derek

TI__Guru**** 393215 points

Hi Huang,

Have you checked all components and traces on the TX line? Or maybe the processor is not soldered OK? I can see no other reason. UART0_TX pin comes out of reset with pullup enabled and should be high by default.

Best Regards

Biser

0 Huang Derek over 12 years ago in reply to Biser Gatchev-XID

Intellectual 360 points

Hi Biser,

We have checked the TX line and solder. they are right.

now the UART0 on our experimental board sends other strange characters.

We have a question.

when the power-on timing of experimental board is not totally correct,

will it influence the data sent by UART0?

0 Biser Gatchev-XID over 12 years ago in reply to Huang Derek

TI__Guru**** 393215 points

Hi Huang,

The UART settings on your PC should be 115200, 8, N, 1. Here is a link on UART boot:

http://processors.wiki.ti.com/index.php/AM335x_U-Boot_User%27s_Guide#UART_2

As for power-on timing, yes it could influence proper processor start-up. The SYSBOOT values are sampled at reset release time, for example. How does your timing differ from the datasheet recommendations?

Best Regards

Biser

0 Huang Derek over 12 years ago in reply to Biser Gatchev-XID

Intellectual 360 points

Hi Biser,

Becuase we chose EEPROM mode of TPS65910A1,

Our power-on timing is PWRHOLD --> VDD_MPU --> 3.3V --> 1.8V -->MPU_ PORZ.

And the specification that we referred is "swcu093b".

By the way, is there any difference between TPS65910A1RSL and TPS65910AA1RSL? Such as power-on timing, voltage level ect...

The below picture is our power-on timing.

thank you.

0 Biser Gatchev-XID over 12 years ago in reply to Huang Derek

TI__Guru**** 393215 points

Hi Huang,

The proper PMIC for AM335X with DDR2 memory is TPS65910AA1RSL. Please check the following document: http://www.ti.com/lit/ds/swcs046q/swcs046q.pdf (Table 1). The document you refer to is the TPS65910Ax User's Guide For AM335x Processors, with the proper part numbers in listed in the body text of section 1 (above Table 1).

Yes, there are timing differences between TPS65910A1RSL and TPS65910AA1RSL.

0 Huang Derek over 12 years ago in reply to Biser Gatchev-XID

Intellectual 360 points

Hi Biser,

when the EV board of AM335X is in UART mode and powers up, the first byte sent by the UART0 is 0x00.

after that, the rest of bytes sent by UART0 are 0x43.

why is the first byte sent by UART0 0x00?

by the way, when the EV board of AM335x is in other modes, the first byte sent by UART0 is also 0x00.

0 Biser Gatchev-XID over 12 years ago in reply to Huang Derek

TI__Guru**** 393215 points

Hi Huang,

Are you sure it's the UART that sends 0x00? Maybe the TX line isn't initialized yet. It's high-Z during reset, and maybe this is what your terminal interprets as 0x00. 0x43 is correct behaviour.

0 Huang Derek over 12 years ago in reply to Biser Gatchev-XID

Intellectual 360 points

Hi Biser,

we use the other software application monitoring data from COM in PC.

and this software prints data received from COM.

now, our board keeps sending 0x00, after we changed TPS65910A1RSL to TPS65910AA1RSL.

0 Biser Gatchev-XID over 12 years ago in reply to Huang Derek

TI__Guru**** 393215 points

Hi Huang,

I am sorry, but I really cannot debug PCB's over forum posts. If you would like, you can send a schematic/layout review request through your local TI FAE/representative.

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the UART boot for AM3357