range of custom pcb

RE: range of custom pcb

FormerMember — Mon, 30 Jul 2018 12:08:04 GMT

The fix looks fine, what is the range now?

RE: range of custom pcb

sathish2307 — Fri, 20 Jul 2018 10:19:04 GMT

I'm developing custom board using nrf52840.

Previously my ex-colleague was developing the board and now I'm taking care of this, so it would be helpful if you could assist me on completing the board.

At present, the board is almost complete and I would need to check the design is correct as per guidelines.

case ID: 207780 - This is the case ID used by the previous developer.

I have attached below the image of the custom board,

Can you please check the board and suggest me if this is correct ?

RE: range of custom pcb

AmbystomaLabs — Fri, 15 Jun 2018 14:12:30 GMT

We are still not communicating correctly. I wanted to see a photo of your board after you fixed your problem with J1.

What I can see from the photo above it looks like you used the mostly correct artwork for the micro coax test port. But what you did wrong is that you placed the wrong connector for J1 instead of a micro coax test port.

To fix this problem you can either buy the correct microcoax test port and place it. Or, you can bypass the input and output with a chip cap or small piece of wire. You do not and should not scratch any ground away. That is unnecessary and will keep the micro coax test port from working if you ever buy it.

On your next spin, one thing you should fix is that the ground plane under J1 should be solid and not connected via small traces. This ground plane is important for the connector to work correctly. Similarly the ground pads for the connector should not have thermals. It should connect connect solidly to the surrounding ground and vias should be placed close to or even in the ground pad.

For reference here is the correct artwork for the testport from the DK pcb:

Please note the two vias inside of the ground pad. These are very important. Simply placing them off to one side as you did is not sufficient. Also note, NO THERMALS!!!

If you don't ever intend to use the testport, and many people have no need for it, you can just bypass it in the artwork. Here is a devzone question about that: https://devzone.nordicsemi.com/f/nordic-q-a/35133/pcb-antenna-nrf52810-eagle-files-does-it-need-extra-components-for-impedance-matching

For your reference this is how you bypass J1. Normally this can be accomplished with a 1206 or 0805 part.:

RE: range of custom pcb

karthikeyan — Fri, 15 Jun 2018 13:27:18 GMT

hi,

i have uploaded the image of pcb before assembly of the components. in that J1 as not scratched.

RE: range of custom pcb

AmbystomaLabs — Fri, 15 Jun 2018 13:21:29 GMT

Well, I'm still not convinced you have your antenna hooked up correctly. It would be nice to see a photo of it correctly hooked up and J1 bypass as you have indicated was completed.

But assuming J1 has been bypassed correctly then your range issues are then a function of impedance matching. They can only be resolved with a VNA and someone who knows how to use it.

RE: range of custom pcb

karthikeyan — Fri, 15 Jun 2018 13:16:22 GMT

hi,

there was little bit problem in distance. how to achieve that?

thanks and regards,

karthikeyan

RE: range of custom pcb

AmbystomaLabs — Fri, 15 Jun 2018 13:14:50 GMT

Ok. That is just different than what you show in your photo above.

RE: range of custom pcb

karthikeyan — Fri, 15 Jun 2018 13:07:03 GMT

hi amby,

the solder team as removed J1 and scrached gnd connections and justed pasted J1 using glue. J1 has been removed.

thanks and regards,

karthikeyan

RE: range of custom pcb

AmbystomaLabs — Fri, 15 Jun 2018 12:52:49 GMT

You did that wrong. You were supposed to remove J1 and jump across input and output. By leaving J1 and removing the ground connection you just left a huge parasitic reactance on your microstrip. You have not hooked up your antenna.

RE: range of custom pcb

karthikeyan — Fri, 15 Jun 2018 08:01:23 GMT

hi,

removed J1 and scratched away the connections to ground where the the connector is placed, and soldered and just pasted J1(it is not placed in pcb). the range of custom pcb is somewhat better now. eg: if PDK distance is 10M. the custom board distance is 8M.

thanks and regards

karthikeyan

RE: range of custom pcb

FormerMember — Fri, 15 Jun 2018 07:46:29 GMT

Could you upload a picture of your PCB with J1 removed?

RE: range of custom pcb

karthikeyan — Thu, 14 Jun 2018 10:31:37 GMT

hi kristin,

i have tested after removing the J1 as per your comment. now its better. but the range is not equal to PDK. what to do next?

thanks and regards,

karthikeyan

RE: range of custom pcb

FormerMember — Mon, 11 Jun 2018 08:10:01 GMT

Did you test the suggestions, remove J1 and do some soldering?

RE: range of custom pcb

karthikeyan — Fri, 08 Jun 2018 07:36:10 GMT

hi,

any solution for this?

thanks and regards

karthikeyan

RE: range of custom pcb

karthikeyan — Thu, 07 Jun 2018 03:55:02 GMT

hi kristin,

i am having another doubt. in ble_proximity example. i have made little changes gave read and write permission to device name and TX power. when ever i write new values from nrf connect mobile app. i captured those values and updated the TX power and device name. this works fine in my nrf52840 pdk. but in custom board when ever the TX power is changed. the system reset and fatal error occurs. so this is also happening because of J1 connector? correct me if i am wrong.

thanks and regards

karthikeyan

RE: range of custom pcb

AmbystomaLabs — Tue, 05 Jun 2018 14:04:03 GMT

Assuming the artwork under J1 supports it, a good bypass will be a 6-20pF chip cap probably 0805 or 1206 package size. It won't be perfect but it should work good enough and let you continue work if you don't have the testport connector at hand.

Or a short piece of wire will work too.

RE: range of custom pcb

karthikeyan — Tue, 05 Jun 2018 13:58:40 GMT

thanks both kristin and ambystomalabs i will test with both the ways and let u know.

regards

karthikeyan

RE: range of custom pcb

AmbystomaLabs — Tue, 05 Jun 2018 13:54:50 GMT

As Kristin pointed out, you placed the wrong connector at J1. Your micro-coax connector has a ground connection where your antenna is hooked up. I believe you thought you had bought the testport connector. They look similar.

You can either pull J1 and bypass or just place the correct test port connector. Or, hook up an antenna via micro-coax.

Here is a link to the MuRata testport connector that most people use. You have to use a special probe with it. You cannot use a standard micro-coax connector.

https://www.digikey.com/product-detail/en/murata-electronics-north-america/MM8130-2600RA2/490-4981-1-ND/1775925

RE: range of custom pcb

FormerMember — Tue, 05 Jun 2018 13:23:51 GMT

After looking at the PCB, I think the problem is related to J1. J1 is a connector like this?

As you can see on p. 3 in that datasheet, there is no connection through the connector, it means that the antenna is not connected to the radio. Could you remove J1, scratch away the connections to ground where the the connector is placed, and solder so that the antenna is connected to the radio? And then test again?

RE: range of custom pcb

karthikeyan — Tue, 05 Jun 2018 12:18:13 GMT

hi kristin,

i assume that you read all the comments in that previous ques. so i cant go for a another pcb design and prototype. want to make changes in this itself rather than going for a new design.

[quote userid="2371" url="~/f/nordic-q-a/35044/range-of-custom-pcb/134727"]Do you have a spectrum analyzer available? If so, could you use the spectrum analyzer to measure the output frequency? (The radio_test example can be used for testing.)[/quote]

sorry i am not having the spectrum analyzer.

[quote userid="2371" url="~/f/nordic-q-a/35044/range-of-custom-pcb/134727"]J1: I assume that a switch is placed on J1, so that the output of the radio is connected to the antenna?[/quote]

thanks and regards

karthikeyan

RE: range of custom pcb

FormerMember — Tue, 05 Jun 2018 12:08:54 GMT

I suspect the range problem could be related to the 32 MHz crystal, because C8 is placed far from the crystal.

Do you have a spectrum analyzer available? If so, could you use the spectrum analyzer to measure the output frequency? (The radio_test example can be used for testing.)

J1: I assume that a switch is placed on J1, so that the output of the radio is connected to the antenna?

RE: range of custom pcb

karthikeyan — Tue, 05 Jun 2018 10:21:46 GMT

hi kristin,

this is the Case ID: 206489

RE: range of custom pcb

FormerMember — Tue, 05 Jun 2018 09:38:19 GMT

What is the case number on the other case?

RE: range of custom pcb

karthikeyan — Tue, 05 Jun 2018 06:35:37 GMT

hi kristin,

any update?

regards,

karthikeyan

RE: range of custom pcb

karthikeyan — Mon, 04 Jun 2018 08:35:36 GMT

hi kristin,

already there was a private question with the heading "custom board programming fails" which i closed on last friday. there i have attached the gerber file and BOM. if you cant check it. i will upload gerber. but how can i make the case private?

thanks and regards,

karthikeyan