LED placement on Bluetooth TX & RX pins in nRF51822

RE: LED placement on Bluetooth TX & RX pins in nRF51822

SaadInam — Tue, 29 Sep 2020 14:41:57 GMT

You are completely right RK. 4 years ago I was a bit of new person in electronics and layouts. I am actually very embarrassed to read my questions and replies here. But thankfully I can understand everything the commenters have said 4 years later 🙂

RE: LED placement on Bluetooth TX & RX pins in nRF51822

RK — Mon, 25 Jul 2016 10:34:23 GMT

I don't think the OP understands those are the 2.4GHz antenna outputs for some reason and thinks they are UART lines despite awneil trying to explain it.

RE: LED placement on Bluetooth TX & RX pins in nRF51822

Øyvind Karlsen — Mon, 25 Jul 2016 08:49:53 GMT

Hi,

It is a very bad idea to place LEDs and transistors on ANT1 and ANT2, these are differential outputs for the 2.4 GHz radio signal. Normal transistors and LEDs are not rated for anything near this frequency and will not work, actually it is very likely that they will become hot and break.

The reference design should be followed, there's also a tutorial on general PCB design guidelines.

Best regards,

Øyvind

RE: LED placement on Bluetooth TX & RX pins in nRF51822

awneil — Sun, 24 Jul 2016 21:17:56 GMT

No, you can't.

RE: LED placement on Bluetooth TX & RX pins in nRF51822

SaadInam — Sun, 24 Jul 2016 19:39:35 GMT

What will be TX/RX in this case? Please can you help me a lil bit. Can i place LEDs on the ANT1/ANT2 lines if not then why?

RE: LED placement on Bluetooth TX & RX pins in nRF51822

awneil — Sun, 24 Jul 2016 19:12:15 GMT

Again, ANT1 and ANT2 are the radio antenna - or "aerial" - connection points; so this is where the RF energy is transmitted and received.

It is way beyond the scope of a forum post to describe how radio transmission works!

RE: LED placement on Bluetooth TX & RX pins in nRF51822

SaadInam — Sun, 24 Jul 2016 19:08:43 GMT

can you tell me what will happen to the TX and RX for this case? And what is the need of ANT1 and ANT2? I saw the product specification but couldn't understand

RE: LED placement on Bluetooth TX & RX pins in nRF51822

awneil — Sun, 24 Jul 2016 18:53:17 GMT

As quoted above, these are the antenna connection points.

Have you looked at the product specification?

Or the reference designs: www.nordicsemi.com/.../nRF51822

Or the schematics of the Dev Kits, Dongles, etc: www.nordicsemi.com/.../nRF51822

RE: LED placement on Bluetooth TX & RX pins in nRF51822

SaadInam — Sun, 24 Jul 2016 18:47:46 GMT

when would i use ANT1 or ANT2 ? And does this mean that TX and RX are on the same line so i have to place only when status LED?

RE: LED placement on Bluetooth TX & RX pins in nRF51822

awneil — Sun, 24 Jul 2016 18:33:51 GMT

www.nordicsemi.com/.../nRF51822

Pin functions are described on p12 of the Product Specification (v3.1):

ANT1 RF Differential antenna connection (TX and RX).

ANT2 RF Differential antenna connection (TX and RX).

Note that these are the RF connections - you would not connect these to an MCU!

Presumably, your diagram is intended to indicate a UART connection to the MCU ... ?