NRF51822+PA

[andy2003hunan]

i want to add a PA for a nrf51822 chip inorder to extend the coverage. i choosed a PA IC named RFX2401C.i am wondering how to deal with the TX pin and RX pin of RFX2401C.could you enginners give me some advise on how connect a nrf51822 and a RFX2401C?and how to deal with the firmware. tks!

[FormerMember]

Hello,

You can connect the RX/TX switch to VDD_PA. This pin will go high (1.8V) when the TX is active and is low in standby and in RX mode. If you invert the signal, you have both RX enable and TX enable. Alternativly, use a IO to controll RX EN in other to switch off the PA and connect VDD_PA to TX EN.

Regards, Kristin

[andy2003hunan]

I mean,i want to use two IOs to control the TX _EN and RX_EN pins of PA.When the transiceiver is in TX mode,i enable the TX_EN pin and disable the RX_EN pin of PA,and when the transiceiver is in RX mode,i should disable the TX_EN pin and enable the RX_EN pin. The question is how do i know the states of transiverver when the NRF51822 runs BLE stack? Can i read the register named radio_states to know the states of the NRF51822 then i control the TX_EN and RX_EN pin?

Could you emploees give me a clear solution,if you can give me a reference,i will preciate.

Than you very much!

[Janek Mann]

Hi Andy,

the advice you got from Kristin is sensible; It is not possible to get a signal from the soft device every time the protocol changes RX/TX mode (it wouldn't be practical given the precise timing requirements of Bluetooth LE, anyway), so your best bet is to use the VDD_PA pin to control the RX/TX switch in the RFX2401C. I have implemented the same scheme in the past with NRF24L01+ with good success.

Note the truth table on page 5 of the RFX2401C data sheet; the TXEN pin of RFX2401C takes precedence over the RXEN pin so you can use GPIO to turn on the RXEN pin and leave the control of the TXEN pin to the VDD_PA pin.

I believe you should be able to use the radio_notification callback from the soft device to turn the RXEN pin on before the soft device carries out radio activity, saving power.

Cheers, Janek

[wangyong]

Hi Janek,

Can you please give more detailed information how to use radio notification callback to turn on RXEN pin to save power? We are now using on_ble_evt connect event to turn on RXEN which I believe it is too late... Thanks !