51822 + PA

[wangyong]

Hi everyone. I want to add RFX2411N to extend BLE signal coverage. I also need to minimize power consumption. I used VDD_PA to control TXEN and 2 gpios control both TXEN and MODE. The PA is set to bypass mode by default. I turn on the TXEN when on_connect evt is fired by stack. But I don't think this is the right place to turn on TXEN. Can someone tell me whether my configuration is correct and when to turn on TXEN? Thanks a lot!

[MartinBL]

Hi,

The VDD_PA is high in TX mode and low in RX and standby mode. The way I read this truth table from the RFX2411N datasheet you can leave the RXEN pin high and toggle between PA and LNA mode simply by setting TXEN high or low respectively.

So maybe it would be possible to do something like this:

1. Use radio notifications to generate an interrupt whenever the radio is about to ramp up or power down.
2. Use this interrupt and a GPIO pin to toggle RXEN. Set it high when the radio ramps up, and back to low again at the end of the radio event. This will ensure that your Booster is in Shutdown mode whenever the radio is inactive.
3. Connect VDD_PA to TXEN and let this control the switching between PA and LNA mode.

Regardless, turning on TXEN when the on_connect event is fired isn't very elegant. At that point your master and slave have already started exchanging radio packets, meaning that by using the on_connect event you can only connect without using your Booster. I.e. you don't get the benefit of the Booster and long range until after you have connected.

[MartinBL]

I can't see why not. Just make sure to read the datasheets for the RFX2411N and whatever battery you are using and take note of the maximum currents you can expect and evaluate it with respect to the battery's internal resistance and max output current.