AM4372: Custom board boot issues

Gush Bhumbra

Part Number: AM4372
Other Parts Discussed in Thread: TPS65218

I have a new board design using the AM4372 and the recommended PMIC TPS65218. All the voltage rails are correct and the oscillator is running by the time the PORZ pin is released to high by the PMIC to start the CPU but on our boards (We have 3 prototypes) the CPU does not reliably start the ROM bootloader. The SYSBOOT boot pins are configured to boot from SDCARD and between 10 and 75% of the time the CPU will start correctly depending on which board we try.

Any guidance of where to look for problems would be appreciated.

over 8 years ago

0 Biser Gatchev-XID over 8 years ago

TI__Guru**** 393215 points

One thing that you should check is whether the SYSBOOT pins are at the required voltage levels at reset release time. Please also check processors.wiki.ti.com/.../AM437x_Schematic_Checklist especially the MMC requirements. If the MMC traces are too long (>10cm), this could be a problem too. Have you tried to boot from another source, e.g. UART?

0 Gush Bhumbra over 8 years ago in reply to Biser Gatchev-XID

Prodigy 200 points

Hi Biser,

Yes, I double checked the schematic checklist. Yes I checked the SYSBOOT pins are all stable and correct before PWRONRSTN goes high.

The device will reliably boot from the UART and from the MMC0/SD peripherals, once the CPU starts running ROM code. However the problem is the boot process will not reliably start executing ROM code. PWRONRSTN always transitions correctly. The WARMSRTN signal always follows PWRONRSTN correctly. Just the ROM code will not start executing.

Regards,

Gush.

0 Biser Gatchev-XID over 8 years ago in reply to Gush Bhumbra

TI__Guru**** 393215 points

There may be something wrong in the design then. Can you post the schematics?

0 Gush Bhumbra over 8 years ago in reply to Biser Gatchev-XID

Prodigy 200 points

I am only allowed to do this after an NDA is setup. Also can you tell me an email address to send NDA/ schematic files?

0 Biser Gatchev-XID over 8 years ago in reply to Gush Bhumbra

TI__Guru**** 393215 points

I'm sorry, this cannot be done over the forum. It will have to go through your nearest TI representative. What I can suggest is you carefully check your design against the AM437x reference designs: processors.wiki.ti.com/.../AM437X_EVM_Boards

This wiki may also be useful to you, even though it's for AM335x: processors.wiki.ti.com/.../AM335x_board_bringup_tips

0 Biser Gatchev-XID over 8 years ago in reply to Biser Gatchev-XID

TI__Guru**** 393215 points

Thanks. I got the schematic from your TI rep.

What I notice is that you are using the AM437x EMU0 and EMU1 pins, probably as GPIO. These pins are part of the ICE logic and must be both high at reset release time. Otherwise the device may enter the "wait-in-reset" state. You should place 4.7kOhm external pullups to VDDSHV3 on both EMU0 and EMU1. Please let me know the results.

0 Gush Bhumbra over 8 years ago in reply to Biser Gatchev-XID

Prodigy 200 points

Yipee! That fixed it. I'm not sure how I would have worked that one out without your help.Thanks!

0 Gush Bhumbra over 8 years ago in reply to Gush Bhumbra

Prodigy 200 points

Can you tell me if these pins need pullups if they are not connected to anything eg unused as GPIOs? Also are there any other pins that need pulling to a specific level on reset? Also does the VSS_RTC pin need to be externally connected to GND as the GP-EVM board does not make this connection, but the datasheet requires it.

0 Biser Gatchev-XID over 8 years ago in reply to Gush Bhumbra

TI__Guru**** 393215 points

Great! Glad you solved this. Yes it's strongly recommended to have external pullups on EMU0 and EMU1 even if they are unused. They do have internal pullups switched on by default, but these are weak pullups and relying just on them is not recommended (as you have seen yourself).

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AM4372: Custom board boot issues