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Hot!RN4871 low-power mode while connected

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2020/04/12 19:49:57 (permalink)

RN4871 low-power mode while connected

Hi folks,
Based on Appendix C of the RN4871/70 User's Guide, my understanding is that there are two low power modes:

1. Dormant (lowest power): No RF communication, so can't mantain a BLE connection (?)

2. Low power: device clocked at 32 kHz, BLE connection maintained. 16 MHz UART clock off so UART is dead - device can't accept data for BLE transmission. If SO,1 has been issued, this mode is entered by setting UART_RX_IND high. To reactivate the UART (so device can accept data for BLE transmission), UART_RX_IND must be pulled low and after waiting 5 ms, data can be sent to the UART.

I'm interested in the low power mode. I'm trying to connect two BLE devices, then put the RN4871 into the low power mode while a microcontroller collects and prepares some data. Every second, I want to enable the UART, dump data into it and then go back into the low power mode.

I'm using firmware revision 1.40. All configuration is default except for SO,1 (enable the low power mode); SB,04 (baud rate = 57.6k) and SS,40 (only enable transparent UART service)

I have the low-power mode working as expected (UART_RX_IND high = low current & UART inactive; UART_RX_IND low = high current & UART active) as long as the RN4871 is not connected to another device. However, if it is connected to a Bluetooth 4.0 device on a laptop (initiated by the laptop), regardless of the state of the UART_RX_IND pin, the UART remains active and permits communicating with the RN4871. If I drop connection from the PC side, the low power mode again works as expected.

Does anyone have the low-power mode working while maintaining a BLE connection?

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    Re: RN4871 low-power mode while connected 2020/06/10 22:08:56 (permalink)
    I just tested this tonight and I ran into the same issue.  If nothing is connected then the UART acts as expected , but when I am connected to a device, the UART is always active no matter the level of RX_IND.  I am not sure what is going on. 
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