Place nRF52840-QIAA-D0 in custom board

RE: Place nRF52840-QIAA-D0 in custom board

Håkon Alseth — Thu, 06 Feb 2020 10:52:16 GMT

[quote user="francisco.colaco"]Is there anything in sdk_config.h that I need to configure so that the radio works without VDDH or VBUS?[/quote]

No, if the CPU boots, the radio will also be powered.

8 pF CL gives:

C = 2CL - Cpin = 2*8 - 4 = 12 pF, so your loading is correct.

[quote user="francisco.colaco"]At the oscilloscope there is effectively 8 periods every 250ns, measured between peaks, so the frequency seems to be correct. Timing seems to be not an issue, at the least in what pertains to HF crystal.[/quote]

Note that you're loading the crystal with your probe when testing this way. In most cases, this will give a incorrect load, thus a low amplitude and possibly incorrect frequency. If your probe has low capacitance, which it seems to do as your measurements are per the crystal spec, then it should work just fine.

Could you check these as well? With Q2, I mean the RF frequency output. These are the advertising frequencies that you should see:

[quote user="hkn"][/quote]

Q1: How about other bluetooth examples? Do they also behave like this?

Q2: Do you have access to a spectrum analyzer? If yes; You can check if the device outputs on the correct frequency.

Kind regards,

Håkon

RE: Place nRF52840-QIAA-D0 in custom board

francisco.colaco — Thu, 06 Feb 2020 10:36:41 GMT

The crystal is 8pF, MCSJK-7E-32.00-8-10-60-B-10. 10ppm error.

At the oscilloscope there is effectively 8 periods every 250ns, measured between peaks, so the frequency seems to be correct. Timing seems to be not an issue, at the least in what pertains to HF crystal.

Is there anything in sdk_config.h that I need to configure so that the radio works without VDDH or VBUS?

Thanks for your help.

RE: Place nRF52840-QIAA-D0 in custom board

Håkon Alseth — Thu, 06 Feb 2020 10:24:55 GMT

[quote user="francisco.colaco"]Two prototypes exhibit identical behaviour. Nothing is shorted at the antenna path.[/quote]

Q1: How about other bluetooth examples? Do they also behave like this?

Q2: Do you have access to a spectrum analyzer? If yes; You can check if the device outputs on the correct frequency.

It might be that the crystal is loaded incorrectly, which will drag the frequency, resulting in the radio not operating on the exact frequency that you want it to.

Q3: Do you have the details of the crystal that you have mounted? I'm particularly interested in the "CL" value of your mounted HF crystal.

Kind regards,

Håkon

RE: Place nRF52840-QIAA-D0 in custom board

francisco.colaco — Wed, 05 Feb 2020 14:01:50 GMT

Two prototypes exhibit identical behaviour. Nothing is shorted at the antenna path.

RE: Place nRF52840-QIAA-D0 in custom board

Håkon Alseth — Wed, 05 Feb 2020 13:38:09 GMT

Hi,

Could you try another bluetooth example, to see if that works?

If not, can you check there's nothing shorted in the antenna path?

Do you have more than one prototype that exhibits this behavior?

Kind regards,

Håkon

RE: Place nRF52840-QIAA-D0 in custom board

Doroana — Wed, 05 Feb 2020 12:13:30 GMT

Hi,

At the start of main() we run the following snippet:

NRF_CLOCK->TASKS_HFCLKSTART=1;
while(NRF_CLOCK->EVENTS_HFCLKSTARTED == 0);

/* Use external LF CLK */
NRF_CLOCK->LFCLKSRC = 0;
NRF_CLOCK->TASKS_LFCLKSTART=1;

while(NRF_CLOCK->EVENTS_LFCLKSTARTED == 0); NRF_POWER->DCDCEN0 = 0x00;

NRF_POWER->DCDCEN = 0x00;

//NRF_UICR->EXTSUPPLY = 0x00;

The clock inits are passed both on the Devkit and on our board.

We have tried also to make sure DCDEN and DCDEN0 were disabled, but the result is the same. GPIO and PWM and SAADC work on both boards as expected.

The only difference is that the radio only works on the devkit, with the same firmware (the same .hex file).

King Regards

RE: Place nRF52840-QIAA-D0 in custom board

Håkon Alseth — Wed, 05 Feb 2020 11:30:38 GMT

Hi,

Did you run the snippet wrt. the clock sources successfully on your board?

The softdevice does not block if the external HFCLK cannot be started properly, so then all your logs and so-forth will still run and be printed, but the radio will not work, as its not clocked from a accurate enough source.

Kind regards,

Håkon

RE: Place nRF52840-QIAA-D0 in custom board

Doroana — Wed, 05 Feb 2020 11:02:15 GMT

Hi,

We had already cut the trace from VBUS to +3.3V. Yet, the radio did not work, or at the least no advertisement was sensed.

I refer to the datasheet that the configuration 6 (which has no USB) grounds VUSB.

Should I ground it or leave it floating?

Rejecting USB, I have followed configuration 6 very closely for a board revision.

The firmware code we have made does run on the development kit, and the advertisement is sensed with NRF Connect. That makes me think that we are dealing with RF power supply, probably through misconfiguration, since there is VUSB on the development kit.

We just want to make sure that the hardware issues are over before concentrating on software, and that there is a way to make the radio work without the need to supply 5V.

Thanks for your help.

RE: Place nRF52840-QIAA-D0 in custom board

Håkon Alseth — Wed, 05 Feb 2020 08:34:21 GMT

Hi,

[quote user="Doroana"]So in case VUSB is not connected to +5V, must it be grounded? Is the radio supply dependent on VUSB?[/quote]

It should be left unconnected if the correct voltage is not present. I would recommend that you cut the pcb trace to ensure you are within specification.

The problem is that you are providing a voltage which is lower than the operating conditions for VBUS, which is not tested for, so I cannot state if this has a large impact for other parts of the system as the behavior is out-of-spec.

[quote user="Doroana"]Can the USB regulator be shut off by software only?[/quote]

The USB is started if you enable the USBD peripheral. How the voltage regulator behaves when starved (ie: voltage is below the specification), is unfortunately not something I can comment on, as its out-of-spec. As mentioned, I would recommend that you cut the PCB trace, so that the VBUS pin is not powered.

Kind regards,

Håkon

RE: Place nRF52840-QIAA-D0 in custom board

Doroana — Tue, 04 Feb 2020 18:21:06 GMT

Hi,

We have noticed that we have not connected the VUSB to +5V.

So in case VUSB is not connected to +5V, must it be grounded? Is the radio supply dependent on VUSB?

Can the USB regulator be shut off by software only?

RE: Place nRF52840-QIAA-D0 in custom board

Håkon Alseth — Mon, 03 Feb 2020 12:28:29 GMT

Hi,

The configuration that seems to fit your design is this one:

https://infocenter.nordicsemi.com/topic/ps_nrf52840/ref_circuitry.html?cp=4_0_0_6_2#unique_1634453376

You seem to be powering VBUS pin with 3.3V, which is too low according to the specifications:

https://infocenter.nordicsemi.com/topic/ps_nrf52840/recommended_op_conditions.html?cp=4_0_0_7

VBUS should be connected to the USB connector supply voltage.

The values of the matching network is also a bit off (range will suffer), but you should be able to connect to the device over BLE, provided that clock sources and so forth are connected properly.

[quote user="Doroana"]We thank your prompt response. We are using the internal RC oscillator, with the normal code. The same block of code (executable) runs and advertises on the Development Kit. [/quote]

Were you able to run the below mentioned code in the start of main, without any issues?

[quote user="Doroana"][/quote]

As we have enclosed the schematic, are all supply lines and GND lines OK?

Is there a way to check internally the state of the RF line (diagnostics, for instance)?

Please create a private ticket if you want the layout to be checked by nordic.

Kind regards,

Håkon

RE: Place nRF52840-QIAA-D0 in custom board

Doroana — Mon, 03 Feb 2020 12:08:42 GMT

Hi,

We thank your prompt response. We are using the internal RC oscillator, with the normal code. The same block of code (executable) runs and advertises on the Development Kit. As we have enclosed the schematic, are all supply lines and GND lines OK?

Is there a way to check internally the state of the RF line (diagnostics, for instance)?

Best regards,

RE: Place nRF52840-QIAA-D0 in custom board

Håkon Alseth — Mon, 03 Feb 2020 08:27:09 GMT

Hi,

I would recommend that you start by checking your clock sources, mainly the HF and LF clk.

You can start them manually like this:

NRF_CLOCK->TASKS_HFCLKSTART=1;
while(NRF_CLOCK->EVENTS_HFCLKSTARTED == 0);

/* Use external LF CLK */
NRF_CLOCK->LFCLKSRC = 1;

NRF_CLOCK->TASKS_LFCLKSTART=1;
while(NRF_CLOCK->EVENTS_LFCLKSTARTED == 0);

If you hang in one of the above while-loops, it indicates issues starting up the respective clock. You should then check the soldering and see if there's anything out-of-the-ordinary.

Kind regards,

Håkon