LR1121
User Manual Rev 1.1
UM.LR1121.W.APP Mar 2023
19 of 130
Semtech
Proprietary & Confidential
www.semtech.com
2.1.7 RX Mode
RX mode receives incoming RF packets on the RFI_N_LF0/RFI_P_LF0 pins in the sub-GHz band (150-960MHz) , and the
RFIO_HF pin in the 1.9-2.1GHz Satellite band and 2.4GHz band (2400-2500MHz), using one of the modems (LoRa or (G)FSK).
The device enters RX mode using command SetRx(...). At packet reception, an RX_DONE interrupt is generated, and
the received data is stored in the device data buffer. The RX operation can be automatically terminated after a packet
reception, duty-cycled or infinite, based on the application requirements.
While in RX mode, the LR1121 operates in different sub-modes:
• Continuous mode, the device remains in RX mode and looks for incoming packets until the host requests a different
mode.
• Single mode, the device automatically returns to a configured mode (Standby RC by default) after a packet reception.
• Single with timeout mode, the device automatically returns to a configured mode (Standby RC by default) after a
packet reception or after the given timeout. If a sync word (G)FSK or a LoRa header is detected, the timeout is stopped.
• RX Duty Cycle mode, the device goes periodically into RX mode to receive a packet before going back to Sleep mode,
until a packet is received.
• AutoTx mode (auto transmits a packet a given time after packet reception), the device goes into an intermediary mode
for the requested time after a packet reception, before entering TX mode to transmit the packet.
2.1.8 TX Mode
TX mode transmits RF packets using the selected sub-GHz PA on the RFO_LP_LF or RFO_HP_LF pins in the sub-GHz band
(150-960MHz) , and the RFIO_HF pin in the 1.9-2.1GHz Satellite band and 2.4GHz band (2400-2500MHz), using the modems
(LoRa, (G)FSK, or LR-FHSS).
After ramping-up the PA, the LR1121 transmits the data buffer at the given frequency, PA, output power and packet and
modulation configurations. When the last bit of the packet has been sent, a TX_DONE interrupt is generated, the PA
regulator is ramped down, the selected PA is switched OFF and the device goes back to Standby RC or Xosc mode,
depending on the FallBackMode configuration.
In TX mode, the BUSY signal goes low as soon as the PA has ramped-up and transmission of the preamble starts.
While in TX mode, the LR1121 operates in different sub-modes:
• Single mode, the device automatically returns to a configured mode (Standby RC by default) after a packet
transmission.
• Single mode with timeout, the device automatically returns to a configured mode (Standby RC by default) after a
packet transmission or after the given timeout.
• AutoRX mode, (automatically goes into RX mode a given time after transmitting a packet) the device goes into an
intermediary mode for the requested time after a packet transmission, before entering RX mode for reception of a
packet or until the configured timeout.
• Continuous Wave mode (CW mode), the device indefinitely transmits an unmodulated carrier at the predefined
frequency until another command is issued to change the mode.
• Infinite preamble mode: the device indefinitely transmits an infinite preamble of the configured modulation.
To Next Page
Loading...
