X-Nucleo-NFC06A1 - board questions (cap + output power)

[EAnde.1]

Hi 

I’m hardware engineer and are about to develop a NFC product using a ST25R3916. I have bought evaluation kit X-Nucleo-NFC06A1 and have designed my circuit based on this evaluation board with same component selection.

I have some question regarding the board.

1. When the board are using low power mode with capacitance wake-up function I expected CSI and CSO where used together with the capacitance antenna on the evaluation board to wake up the system. However it seams from my point of view, that the added capacitance antenna are not used in this case and “only�? the main 4 turns antenna. The reason for my findings are because I have unmounted R200 and R202. Furthermore have I cuttet the CSI and CSO traces on the board. The board still wake up by using low power mode capacitance wake up when a MIFARE or ICODE card comes near the antenna. The reading length are roughly 4 cm. However on my project the reading length are roughly 1cm.
2. Furthermore would it be helpful to know if it is possible to control the output power though the antenna when it’s fully waked-up and uses AAT.

[Ulysses HERNIOSUS]

Hi EAnde.1,

ad 1) I assume you are using X-CUBE-NFC6 software on the board? This software uses inductive wake-up by default. If you want to use capacitive wake-up you need to manually configure it: discParam.wakeupConfigDefault=false and provide your own wake-up config via discParam.wakeupConfig.

ad 2) For adjusting the output power (mainly reducing as our boards typically use max or close to maximum for given antenna and given matching) you can:

1. Adjust the used driver stages
2. Change the regulator settings
3. Play with DAC / AAT/ varicaps to increase/decrease impedance

Best Regards, Ulysses

[EAnde.1]

Hi Ulysses

Thanks for your reply. Yes I uses  X-CUBE-NFC6 software and have modified it to capacitance wake-up function.

1. How does the capacitance wake-up function work? Because from my point of view it doesn't seems, that the CSO and CSI are used for this wake-up function. Are I'm, right? Because on my board I have removed R200 and R202 and cut traces to CSO and CSI and it still detect cards when in low power mode and uses capacitance wake-up function.
2. To control the output power only using SW are by change the regulator settings?

Best Regards

Eddie Andersen

[Ulysses HERNIOSUS]

Hi Eddie,

if the software is correctly configured to make use of capacitive wake-up then the two plates are used. I could imagine that even after removing the plates it still works a bit but at greatly reduced distance. If unsure you can check during low power operation if bit wcap in register 32h (Wake-up timer control) is correctly set.

For changing output power you can change: nibble d_res in 28h, aat_A/aat_B in 26h/27h or reg_s+rege in 2Ch.

Regards, Ulysses