Custom nrf52832 board

RE: Custom nrf52832 board

Kaja — Thu, 05 Dec 2019 12:41:03 GMT

Hi Jonas,

I can't see the routing in your schematic, could you upload the schematic with routing?
You can upload the altium file, if you have done the schematic there as well.

For the layout:
1. Your missing ground plane in top and bottom layer, make solid and large ground planes. This will ensure proper grounding of the center pad, the components, and the antenna efficiency gets better the larger ground planes it sees.
2. Start with the reference designs, the altium files so that you get a good start point for where the components should be places and the ground planes around.
3. The antenna should be placed on the edge of the board, then rotate the chip so that you get the ANT pin facing the antenna:

4. The trace from the radio matching network to the antenna, should be a 50 Ohm transmission line. The calculation of the transmission line will have to be calculated based on the substrate and distance to ground:

In the bottom layer under the transmission line there should be solid ground.

Feel free to upload updated files, when they are ready.

Best regards,
Kaja

RE: Custom nrf52832 board

Jonaswinz — Wed, 04 Dec 2019 11:29:06 GMT

I updated my circuit the second time.

This time I tried to copy the nrf circuit from the Development Kit (parts are also mostly the same). The only big different here, is the the 32.768 Mhz cristal. The Load Capacitance is 6pf not 9pf (dk). Is that a problem ?

Moreover I designed the ble antenna based on the documentations, but my pcb is only 0.6 - 0.8mm height instead of 1.6mm do I have to worry about that?

I copied the NFC antenna from the development kit.

I also added a battery discharge and overcharge protection.

What do you think about the pcb ?

devzone.nordicsemi.com/.../v3_5F00_3.zip

Jonas

RE: Custom nrf52832 board

Kaja — Thu, 28 Nov 2019 09:07:16 GMT

Hi Jonas,

when it comes to battery protection I suggest you check with Microchip since they are your PMU vendor.

The recommendation from us, is what Stian suggested in the link I sent you.

Best regards,
Kaja

RE: Custom nrf52832 board

Kaja — Mon, 25 Nov 2019 16:55:30 GMT

Hi Jonas,

I can't see that you uploaded the new design files. Could you try uploading them again?

I have to come back to you on the battery protection.

Have you made the antenna yourself?

You are welcome to copy our antennas: find the antenna from the dongle in the HW files, or our quarter wave monopole antenna and our NFC antenna, you find it in the HW files on our nRF52 DK.

We have a white paper explaining tuning of the NFC antenna as well. but you do a rough calculation, and then tune the components.

I can help you with tuning of the antennas (NFC and BLE), and tuning of the radio matching components.

I see that this case is public, if you want it to be private, change it to private.

Best regards,
Kaja

RE: Custom nrf52832 board

Jonaswinz — Sat, 23 Nov 2019 00:11:34 GMT

Tanks for your helpfull answer. I updated my schematic...

(Schematic_Beep Wallet_V3.2_20191123005247, BOM_Beep Wallet_20191123005257) Files

Do I need a reverse battery protecten, when my battery is soldert?

I actually ment a overcharge, discharge protection. The documentation of the MCP73831 only mentions a "Under-voltage lockout". Do I still need them to protect my battery ?

I am also not sure how to design the right antennas (event though I read the documentaion). Is it ok to use these antennas:

ble: https://easyeda.com/components/2-4-GHZ-PCB-ANTENNA_5d5dd40b0303432aa7e781c8c4bf77e2

nfc: https://easyeda.com/component/NFC_Antenna_Square-b765644c71744487aa366f684ff1e6f5

I am also not quit sure how to calculate the tune capacitors for the nfc antenna.

Sorry for my many questions. Jonas

RE: Custom nrf52832 board

Kaja — Thu, 21 Nov 2019 09:59:18 GMT

Hi Jonas,

feedback on the circuitry:
1. There should be 4.7 uF capacitor close the the VDD pin 48.
2. Due to errata 138, and that your not using P0.25 and P0.26, you should ground those pins.
3. C18 should be 100nF.
4. C19 should be 100 nF.
5. C22 must be 100 nF.
6. Your 32.768 kHz (mark with right freq. in the schematic) has an CL = 6 pF. Therefore c24 and C23 should be = CL*2 - (~5pF) = 8 or 7 pF.
7. Your 32 MHz crystal has an load capacitance, CL = 10 pF. Then C25 and C26 should be = CL*2 - 4pF = 16 pF.

The parts looks fine, we have recommendations

Yes, and with VDD and ground. Can be smart to set up an interface with pin's. See https://devzone.nordicsemi.com/f/nordic-q-a/20536/programming-external-custom-nrf52832-board-using-nrf52-dk

[quote user=""]- does the battery need a seperate protection circuit?[/quote]

- You can have a look at this: https://devzone.nordicsemi.com/f/nordic-q-a/23534/reverse-current-battery-protection

When it comes to the design:
We have a nice guide
you have our reference design

Antenna design, if you want an easy, low cost antenna you can use our quarter printed monopole antenna for 2.45GHz guide. You can also copy our antennas form our DK's and other designs. But remember to increase the length, so that we have some length for antenna tuning.

I'm happy to review your layout, when you get started with that.

Best regards,
Kaja