LTE modem uses a dedicated three-pin interface for RF interference avoidance towards a companion radio device e.g. an external positioning device or Bluetooth® Low Energy device.
The inputs and outputs for this interface:
- COEX0: Input to the LTE modem from the external device. When active high, indicates that the
external device transceiver is turned on.
- When internal GPS is used, COEX0 can be used as active high control for the external LNA component.
- COEX1: Output from the LTE modem to the external device. Active high time mark pulse, which is
synchronous to LTE system time.
- When internal GPS is used, COEX1 delivers the GPS 1PPS (one pulse per second) time mark pulse.
- COEX2: Output from the LTE modem to the external device. When active high, indicates that the
LTE modem transceiver is turned on.
- COEX2 can also be treated as active low grant from LTE modem to the external device, indicating grant to transmit and receive.
Note: COEX2 pin requires an external pull-down resistor in 100 kΩ size range to be used.
Note: Please refer to nRF9160 modem firmware release notes found under nRF91 FW binaries
downloads concerning availability of COEX signaling feature support".
COEX interface timing in relation to modem state is shown in the figure below.
Figure 1. COEX interface timing
