PN7642 resets when calling LPUART_Init

[clittle]

Same firmware runs fine on devkit OM27642EVK, but when run on our prototype it will reset when calling LPUART_Init.

We are looking for areas to investigate.

[Parmiss]

Hi,

Do you have any updates on this? I have the same issue now but with lpuart example and on the devkit OM27642EVK. 

PN76_Common_Wait(50); makes it reset.

PN7642 SDK 2.12.5

[EduardoZamora]

Hello @clittle,

Hope you are doing well.

By any chance, is your firmware based on any of the lpuart driver examples from the PN7642 SDK? If so, are you adding any other modification to the base source code?

According to the PN7642 Data Sheet, Section 9.6.1.4 UART interface, LPUART shares the pins with I2C, I3C, SPI and USB interfaces. Perhaps your application is trying to implement another peripheral (such as the ones previously mentioned) functionality that can be causing some conflicts with LPUART?

Could you please share the relevant schematics of your design?

Regards,
Eduardo.

[clittle]

Hi Eduardo,

Thanks for the reply.

We also tried using the lpuart_polling example. This runs fine on the devkit. With our board it still resets when calling LPUART_Init, specifically the call to  PN76_Common_Wait(50) inside it. 

Looking at the disassembly it appears that this branch to 0x200ab0 causes the reset, but only on our board. Exact same code runs on devkit.

=====

261 PN76_Common_Wait(50);
00208e18: movs r0, #50 ; 0x32
00208e1a: bl 0x200ab0

=====

I will look at getting the schematic shared.

[EduardoZamora]

Hi,

Could you please provide the marking number of your chipset?

Have you observed the same behavior on another PCB from the same batch? Is it possible for you to perform a swap test by replacing the currently soldered chipset with a new one to confirm is this behavior persists?

I would appreciate it if you could share the relevant schematics.

Regards,
Eduardo.

[clittle]

Hi Eduardo,

We have tried this on multiple prototypes so far with the same results.

Here are the chip markings, I checked on two of our prototypes and they are the same:

7642

C100

v3 01

st02241

Let me know how to share the schematic privately and I can get it your way.

Regards,

[EduardoZamora]

Hi,

Could you please check the behavior of your supply pins, by using an oscilloscope, when the instruction that causes this issue is executed?

Also, the PN7642 needs to be configured by EEPROM for the different power supply options; to make use of them, some chip internal configurations need to be done.

What Power Supply configuration are you using as base for your design? I will recommend comparing your current design against the power supply options described in PN7642 Data Sheet, Section 9.8 Power supply.

Regards,
Eduardo.

[clittle]

Hi Eduardo,

Thanks for the update. We can probe the power pins while running the instruction. Based on the datasheet section 9.8 you mentioned we are using example 1 like in  9.8.3.4/figure 22.

A few questions:

- which power pins in particular should we focus on when probing with the scope?

- Which EEPROM settings should we look at first that could affect the LPUART?

Thanks,

[EduardoZamora]

Hi,

You could check, for example, VDDIO supply pin.

Also, as an additional test, could you please try the hello_world or blinky demo apps? This is only to check if your device is working with a basic project. Additionally, if those examples are working properly, you can also test the driver_examples > hostif > lpuart demo app and confirm if a similar behavior occurs.

Regards,
Eduardo.

[clittle]

Hi Eduardo,

Any updates?

[EduardoZamora]

Hi,

You can send me a private message and attach the files there.

Regards,
Eduardo.