How do I change radio frequency in the eddystone ble example?

RE: How do I change radio frequency in the eddystone ble example?

ketiljo — Fri, 22 Nov 2019 09:41:09 GMT

The CL value of the crystal is not the same as the value of the load caps. The crystal will see both capacitors in series so the capacitance will be half of the value of the load caps, provided they are equal. In addition you have the pin capacitance of XC1 and XC2 in parallel. The equation then becomes:

Ccap = CL * C - Cpin

Cpin = 4 pF and CL = 12 pH, so you must use use

Ccap = 12 pF *2 - 4 pF = 20 pF

Round down to 18 pF as this is a standard value.

If you load the crystal incorrectly, you will pull the frequency of the crystal. Some radio front end are more sensitive to frequency error that other, so this is why you see problems on only some phone models.

RE: How do I change radio frequency in the eddystone ble example?

SGC — Thu, 21 Nov 2019 16:26:40 GMT

Thank for answering.

Yes, Im using a 32MHz crystal. The CL of the crystal is 12pF and Im using 12pF load caps as well.

The crystal Im using is this: https://www.digikey.com/product-detail/en/epson/TSX-3225-32.0000MF10Z-W6/SER4378CT-ND/7932362

RE: How do I change radio frequency in the eddystone ble example?

ketiljo — Thu, 21 Nov 2019 13:48:00 GMT

That must be caused by something else. All phones should be able to use all advertisement channels. The antenna not contribute to what you see either.

What's the CL value of the 32 MHz crystal and the load caps you are using? Do you have a 32 kHz crystal?

RE: How do I change radio frequency in the eddystone ble example?

SGC — Wed, 20 Nov 2019 17:10:47 GMT

Thanks for you comments.

I wanted to change the frequency/channels because there are some phones that seems to not receive the frames. To be honest, just one phone has give us problems (Samsung A10), we've tested more than 10 different phones and all of them seems to work fine.

We've developed a custom hardware based on the reference desing. The thing is that, with the same software, the phone detects the NRF52-DK development board and not our custom hardware. As I said, we have made a copy of the reference desing.

The only thing we didnt copy is the antenna desing, we have tested with a PCB based antena and with a ceramic one. Neither of them works with the Samsung A10 phone. So we thought that could be a problem with the tx frequency.

Could you give us any input on this problems? Hope you could help us.

Thanks.

RE: How do I change radio frequency in the eddystone ble example?

ketiljo — Wed, 20 Nov 2019 14:36:21 GMT

The softdevice have an option to advertice on only one channel, but doing this may cause the Eddystone example to misbehave. Normal advertising of devices and beacons will happen on all three channels consecutively.

RE: How do I change radio frequency in the eddystone ble example?

SGC — Wed, 20 Nov 2019 13:50:15 GMT

Thanks for your reply.

So, I understand, that is possible to change between the three advertisement channels for beacons (37, 38 and 39). Im I right?

If it is possible to force the use of one channel or another. Could you kindly tell me how can these channels be selected in the software? As I said, Im using the eddystone example provided with the softdevice sdk.

Thanks.

RE: How do I change radio frequency in the eddystone ble example?

ketiljo — Wed, 20 Nov 2019 11:23:18 GMT

You can't really change the frequency of a BLE beacon. It will and shall use the three advertisement channels. Only the softdevice (BLE protocol stack) can change the frequency.

RE: How do I change radio frequency in the eddystone ble example?

FormerMember — Wed, 20 Nov 2019 10:53:01 GMT

I haven’t any idea about these things...
the way you taught us to step by step its amazing.

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