SX127x Component

The SX127x component allows you to configure the SX1276, SX1277, SX1278 and SX1279 transceivers (datasheet) in ESPHome. Transceivers are connected via the SPI Bus. Supported frequencies range from 137 MHz to 1020 MHz. Supported modulations include LoRa, OOK, FSK, GFSK, MSK and GMSK. The SX127x component may be used as a platform for the Packet Transport Component component, enabling sensor data to be sent directly from one ESPHome node to another.

# Example configuration entry
sx127x:
  cs_pin: GPIO18
  rst_pin: GPIO23
  bandwidth: 50_0kHz
  frequency: 433920000
  modulation: OOK
  packet_mode: false
  rx_start: true
  rx_floor: -90

Configuration variables

cs_pin (Required, Pin Schema): SPI chip select pin.
rst_pin (Required, Pin Schema): Reset pin.
dio0_pin (Optional, Pin Schema): Digital IO pin 0.
auto_cal (Optional, bool): Enable automatic image calibration on temperature changes. Defaults to true.
frequency (Required, int): Frequency in Hz of the transceiver.
modulation (Required, enum): Modulation can be OOK, FSK or LORA `.
pa_pin (Optional, enum): Transmitter output pin, can be BOOST or RFO.
pa_power (Optional, int): Transmitter power, range is from 2 to 17 dBm when pa_pin is BOOST and 0 to 15 dBm when using RFO.
pa_ramp (Optional, enum): Transmitter PA ramp, can be 10us, 12us, 15us, 20us, 25us, 31us, 40us, 50us, 62us, 100us, 125us, 250us, 500us, 1000us, 2000us or 3400us.
rx_start (Optional, bool): Start the receiver automatically on boot or after transmitting.

LoRa configuration variables

bandwidth (Optional, enum): Bandwidth can be 7_8kHz, 10_4kHz, 15_6kHz, 20_8kHz, 31_3kHz, 41_7kHz, 62_5kHz, 125_0kHz, 250_0kHz or 500_0kHz.
payload_length (Optional, int): If greater than zero implicit header mode is enabled and the packet size is fixed. If not configured explicit header mode is enabled and variable packet sizes can be used. Maximum length is 256. Must be greater than zero when using a spreading_factor of 6.
crc_enable (Optional, bool): Enables a payload CRC calculation/check.
preamble_size (Required, int): Length of the preamble in symbols, minimum of 6.
spreading_factor (Optional, int): Spreading factor, values range from 6 to 12. Defaults to 7.
coding_rate (Optional, enum): Coding rate, values can be CR_4_5, CR_4_6, CR_4_7 or CR_4_8. Defaults to CR_4_5.
sync_value (Optional, int): Synchronization word, limited to a single byte. The value 0x34 is reserved for LoRaWAN networks and the value 0x12 is meant for private networks. It is recommended to use only 0x12 or 0x34. Defaults to 0x12.

FSK/OOK configuration variables

bandwidth (Optional, enum): Bandwidth can be 2_6kHz, 3_1kHz, 3_9kHz, 5_2kHz, 6_3kHz, 7_8kHz, 10_4kHz, 12_5kHz, 15_6kHz, 20_8kHz, 25_0kHz, 31_3kHz, 41_7kHz, 50_0kHz, 62_5kHz, 83_3kHz, 100_0kHz, 125_0kHz, 166_7kHz, 200_0kHz or 250_0kHz.
packet_mode (Required, bool): In packet mode bytes are sent via the send_packet automation and received with the on_packet trigger. If not enabled continuous mode is used and raw data is sent and received on DIO2.
payload_length (Optional, int): Length of the payload in packet mode. If not configured then the variable length packet format is used. Maximum length is 64.
crc_enable (Optional, bool): Enables a 16 bit CRC calculation/check in packet mode.
bitrate (Optional, int): Bit rate of the signal. Required in packet mode and recommended in continuous mode. Normally the inverse of the bit duration, eg 1 / 208 us is 4800 bps.
bitsync (Required, bool): Enables the receive bit synchronizer. Required in packet mode. Recommended in continuous mode, however if there is no preamble plus high noise it may be better to turn it off.
preamble_polarity (Optional, int): Polarity of the preamble, either 0xAA or 0x55.
preamble_size (Optional, int): Length of the preamble, in bytes, to be sent by the transmitter. This value should be larger than preamble_detect on the receive side to allow time for the receiver’s AFC and AGC to adjust.
preamble_detect (Optional, int): Minimum length of the preamble in bytes required by the receiver. Preamble detector is disabled if the size is 0 and its value capped at 3.
preamble_errors (Optional, int): Number of chip errors tolerated in the receiver.
sync_value (Optional, list): Synchronization bytes, list of 1 to 8 bytes, found after the preamble and before the payload.
rx_floor (Optional, float): When receiving OOK rx_floor should be set appropriately for your environment. If set too high (ie closer to 0) the radio will ignore everything. If set too low (ie closer to -128) too much noise will get through. When receiving FSK without a preamble configured rx_floor is used to trigger the receiver.
deviation (Optional, int): Transmitter FSK frequency deviation, values range from 0 to 100,000 Hz.
shaping (Optional, enum): Transmitter data shaping. In OOK can be CUTOFF_BR_X_2, CUTOFF_BR_X_1 or NONE. In FSK can be GAUSSIAN_BT_0_3, GAUSSIAN_BT_0_5, GAUSSIAN_BT_1_0 or NONE. Not recommended in continuous mode as the data on DIO2 must to be synchronized with the bit clock on DIO1.

ℹ️ Note
Configuration variables can be changed at runtime using lambdas. Settings will only be applied after calling configure. See API Reference .

Triggers

on_packet (Optional, Automation): An automation to perform in packet mode when a packet has been decoded. A variable x of type std::vector<uint8_t> is passed to the automation for use in lambdas. In LoRa mode the variables snr and rssi are also available.

sx127x:
  ...
  on_packet:
    then:
      - lambda: |-
          ESP_LOGD("lambda", "packet %s", format_hex(x).c_str());
          ESP_LOGD("lambda", "rssi %.2f", rssi);
          ESP_LOGD("lambda", "snr %.2f", snr);

Actions

`sx127x.run_image_cal` Action

This action runs the sx127x image calibration, must be in standby mode.

interval:
  - interval: 10min
    then:
      - sx127x.set_mode_standby
      - sx127x.run_image_cal
      - sx127x.set_mode_rx

`sx127x.set_mode_tx` Action

This action sets the sx127x mode to tx.

on_...:
  - sx127x.set_mode_tx

`sx127x.set_mode_rx` Action

This action sets the sx127x mode to rx.

on_...:
  - sx127x.set_mode_rx

`sx127x.set_mode_sleep` Action

This action sets the sx127x mode to sleep.

on_...:
  - sx127x.set_mode_sleep

`sx127x.set_mode_standby` Action

This action sets the sx127x mode to standby.

on_...:
  - sx127x.set_mode_standby

`sx127x.send_packet` Action

This action sends a packet, the sx127x needs to be in packet mode.

on_...:
  - sx127x.send_packet:
      data: [0x1F, 0x3E, 0x06, 0x5F, 0x4F, 0x5F, 0xAC, 0xB1]

Configuration variables

data (Required, list): The packet to send, length should match the configured payload_length.

LoRa

LoRa example using an explicit header, spreading factor 7 and coding rate 4/5.

# Example configuration entry
sx127x:
  dio0_pin: GPIO26
  cs_pin: GPIO18
  rst_pin: GPIO23
  pa_pin: BOOST
  pa_power: 4
  bandwidth: 125_0kHz
  crc_enable: true
  frequency: 433920000
  modulation: LORA
  rx_start: true
  sync_value: 0x33
  spreading_factor: 7
  coding_rate: CR_4_5
  on_packet:
    then:
      - lambda: |-
          ESP_LOGD("lambda", "packet %s", format_hex(x).c_str());
          ESP_LOGD("lambda", "rssi %.2f", rssi);
          ESP_LOGD("lambda", "snr %.2f", snr);

  button:
    - platform: template
      name: "Transmit Packet"
      on_press:
        then:
          - sx127x.send_packet:
             data: [0xC5, 0x51, 0x78, 0x82, 0xB7, 0xF9, 0x9C, 0x5C]

FSK/OOK Packet Mode

FSK packet mode example using a bit rate of 4800.

# Example configuration entry
sx127x:
  cs_pin: GPIO18
  rst_pin: GPIO23
  dio0_pin: GPIO26
  pa_pin: BOOST
  pa_power: 17
  bitrate: 4800
  bitsync: true
  crc_enable: true
  frequency: 433920000
  modulation: FSK
  packet_mode: true
  payload_length: 8
  rx_start: true
  sync_value: [0x33, 0x33]
  preamble_size: 4
  preamble_detect: 2
  preamble_errors: 8
  preamble_polarity: 0x55
  on_packet:
    then:
      - lambda: |-
          ESP_LOGD("lambda", "packet %s", format_hex(x).c_str());

  button:
    - platform: template
      name: "Transmit Packet"
      on_press:
        then:
          - sx127x.send_packet:
             data: [0xC5, 0x51, 0x78, 0x82, 0xB7, 0xF9, 0x9C, 0x5C]

FSK/OOK Continuous Mode

As a Receiver

The sx127x will output demodulated data onto DIO2 and remote_receiver should be used to receive this data on pin (must be wired to DIO2).

# Example configuration entry
sx127x:
  cs_pin: GPIO18
  rst_pin: GPIO23
  bandwidth: 50_0kHz
  frequency: 433920000
  modulation: OOK
  packet_mode: false
  rx_start: true
  rx_floor: -90

remote_receiver:
  pin: GPIO32
  dump: raw

ℹ️ Note
It is not recommended to receive FSK in continuous mode as there will be too much noise. Use packet mode instead.

As a Transmitter

The sx127x expects raw data to be transmitted on DIO2, remote_transmitter should be used to transmit this data on pin (must be wired to DIO2). The sx127x mode must be set appropriately before and after transmit using the on_transmit and on_complete automations.

# Example configuration entry
sx127x:
  cs_pin: GPIO18
  rst_pin: GPIO23
  bandwidth: 50_0kHz
  frequency: 433920000
  modulation: OOK
  packet_mode: false
  rx_start: false
  pa_pin: BOOST
  pa_power: 17

remote_transmitter:
  pin: GPIO32
  carrier_duty_percent: 100%
  on_transmit:
    then:
      - sx127x.set_mode_tx
  on_complete:
    then:
      - sx127x.set_mode_standby

button:
  - platform: template
    name: "Transmit Raw"
    on_press:
      then:
        - remote_transmitter.transmit_raw:
            code: [614, -614, 600, -614, 614, -614, 601, -614]

As a Transmitter & Receiver

The shared pin should to be set to open-drain with a pullup. In remote_transmitter eot_level should be set to false. In addition to setting the sx127x mode in on_transmit / on_complete the pin should be driven low before set_mode_tx and pulled high / released before set_mode_rx.

# Example configuration entry
sx127x:
  cs_pin: GPIO18
  rst_pin: GPIO23
  bandwidth: 50_0kHz
  frequency: 433920000
  modulation: OOK
  packet_mode: false
  rx_start: true
  rx_floor: -90
  pa_pin: BOOST
  pa_power: 17

remote_receiver:
  pin:
    number: GPIO32
    mode:
      input: true
      output: true
      pullup: true
      open_drain: true
    allow_other_uses: true
  dump: raw

remote_transmitter:
  pin:
    number: GPIO32
    mode:
      input: true
      output: true
      pullup: true
      open_drain: true
    allow_other_uses: true
  eot_level: false
  carrier_duty_percent: 100%
  on_transmit:
    then:
      - sx127x.set_mode_standby
      - remote_transmitter.digital_write: false
      - sx127x.set_mode_tx
  on_complete:
    then:
      - sx127x.set_mode_standby
      - remote_transmitter.digital_write: true
      - sx127x.set_mode_rx

button:
  - platform: template
    name: "Transmit Raw"
    on_press:
      then:
        - remote_transmitter.transmit_raw:
            code: [614, -614, 600, -614, 614, -614, 601, -614]