advertising issue with nrf51822 ceaa

[hello_alberto_]

hello,

I've encountered a problem with our own nrf51822 circuit not advertising. Our circuit is exactly the same as what is given as the reference circuitry on the datasheet. We tested the exact same code on the nrF51 DK and worked just fine.

Using an enabled debug log support, it says "fast advertising" but nothing appears on our bluetooth list on our phone. We know that the code doesn't hang somewhere because according to the log, the device goes into slow mode exactly after 3 minutes of fast advertising.

Can you please check my pi-network circuitry? Understanding that it should try to match to 50 Ohms impedance using analyzer and smith chart, would the wire highlighted in yellow on our attached circuit cause our nRF not to advertise at all?

Other significant Information:

• nRF51822 CEAA package, LDO setup
• SDK 9.0.0
• softdevice 110 ver. 8.0.0
• VDD = 2.5V
• External 16Mhz works fine (checked it using it as a timer)
• don't have any button in our circuit
• want to use both RX and TX (coded in this way)
• other peripherals such as GPIO and UART work just ok.

I'd appreciate your advice and help.

Thank you in advance!

[RK]

Where did you get that circuit from? That extra wire just shunts the entire signal to ground, the antenna wouldn't see signal at all, that's not 50 ohms, it's zero.

So yes that would definitely be a problem.

[RK]

Yes with just a balun connected directly to the antenna, as long as the antenna is somewhere near 50 ohms, it'll work. The power and range will suffer the worse the antenna is matched but you should get something. So replace L1 with a 0 ohm resistor and remove the yellow wire and try that. Since the antenna is a chip antenna (if I'm reading it right) the impedence should be not bad as long as you mounted it sensibly and it ought to work ok.