NRF52840: VDD ramp-up to main() time.

RE: NRF52840: VDD ramp-up to main() time.

Hrishi — Thu, 26 Sep 2019 20:53:58 GMT

On the UICR, I did read out the UICR content after power-up. As I described above most locations are FFs except for some of the 'reserved for Nordic firmware design' locations below:

I don't think sending hardware is possible.I am working on something else for now but will come back to this in 2 weeks.

Thanks!

RE: NRF52840: VDD ramp-up to main() time.

Kenneth — Wed, 25 Sep 2019 21:16:14 GMT

Looks good.

Is there any way you can send hardware here we may use to recreate it?

Is there any way you may try with 2V?

Can you read out content of uicr (run nrfjprog --readuicr dump.hex)?

RE: NRF52840: VDD ramp-up to main() time.

Hrishi — Wed, 25 Sep 2019 20:55:45 GMT

Hi Kenneth,

Here's a part of the relevant schematic, which shows how the BMD-340 power pins are connected:

Here's the waveform seen at pin 39 (MCU_RSTn) along with the VDD_1V8 bus

Also for completeness my previous scope capture with the VDD_1V8 rail and the GPIO that gets toggled at the start of the bootloader main.c.

Thanks.

Hrishi

RE: NRF52840: VDD ramp-up to main() time.

Kenneth — Tue, 24 Sep 2019 15:52:48 GMT

Hi, Is there any way you can send hardware here we may use to recreate it?

Is there any way you may try with 2V?

How have you electrically connected the BMD-340? Do you have a table that show pin connections for the module?

Were you able to try: ...open the module to find the exact chip markings?

[quote user="Hrishi"]I guess you are saying that from the time nrf52840 VDD gets above 1.75V (according to the datasheet) to the time the PC enters main.c of the bootloader I should see a time delay muc much less than 4s, correct?[/quote]

That is correct! Starting up an external 32kHz may be in the hundreds of ms, but in your case I assume you are toggling that LED in the beginning of main() so that should not apply.

RE: NRF52840: VDD ramp-up to main() time.

Hrishi — Tue, 24 Sep 2019 15:19:34 GMT

The BMD-340 module is getting that 1.8V VDD bus I shared in the scope shot earlier.

RE: NRF52840: VDD ramp-up to main() time.

Hrishi — Tue, 24 Sep 2019 15:16:26 GMT

I guess you are saying that from the time nrf52840 VDD gets above 1.75V (according to the datasheet) to the time the PC enters main.c of the bootloader I should see a time delay muc much less than 4s, correct?

Hmm this is strange.

RE: NRF52840: VDD ramp-up to main() time.

Kenneth — Tue, 24 Sep 2019 05:58:45 GMT

[quote user="Hrishi"]Could there be something in the boot-up process that may cause a long delay?[/quote]

The below text you write that it takes ~4.5 to enter main(), so it must be electrical. I do not see how software can have anything to do with this no, since it doesn't start running any code here before you enable LED. My best suggestion is to check if VDD = 2V solve the issue (even if that will mean you have to modify the the hardware).

[quote user=""]seeing a ~4.5s (yes seconds!) delay in getting to bootloader main()[/quote]

RE: NRF52840: VDD ramp-up to main() time.

Hrishi — Mon, 23 Sep 2019 17:45:06 GMT

These modules are using nrF52840-QIAA production release 1 silicon. BMD-340 doesn't have anything that would slow the VCC down by 3-4 secs.

I am sure I am missing something somewhere. Could there be something in the boot-up process that may cause a long delay? Although as I mentioned earlier if I use the debugger and run the bootloader project, I do not see this huge a delay.

Thanks.

RE: NRF52840: VDD ramp-up to main() time.

Kenneth — Mon, 23 Sep 2019 17:32:40 GMT

The only explanation I have is that something is charging up, e.g. that even if you supply 1.8V, you have some series resistor/diode that limit the current going to the nRF52840 thereby keep it in some kind of reset state. That is why I wanted you try to tweak up the VDD voltage a bit to see what happens. I assume you are not able to open the module to find the exact chip markings?

RE: NRF52840: VDD ramp-up to main() time.

Hrishi — Mon, 23 Sep 2019 16:10:24 GMT

I am using a BMD-340 module.

RE: NRF52840: VDD ramp-up to main() time.

Hrishi — Mon, 23 Sep 2019 16:07:50 GMT

Hi Kenneth,

I can not try with 2V because this is in a system powered with a 1.8V regulator. As seen in my scope shot the bus looks clean.

I checked the UICR after power-up most locations are FFs except for some of the 'reserved for Nordic firmware design' locations below:

Does this tell you anything? Where else could I be looking to debug this issue?

Thanks.

RE: NRF52840: VDD ramp-up to main() time.

Kenneth — Mon, 23 Sep 2019 12:08:03 GMT

Hi,

Do you see the same problem if you are using VDD = 2.0V?

Is this measured close to the VDD pin?

What is the content of UICR after power up? Type: 'nrfjprog --readuicr dump_uicr.hex'

Any schematic to share?

Best regards,
Kenneth