CC1101 Low-Power Sub-1 GHz RF Transceiver

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CC1101 Low-Power Sub-1 GHz RF Transceiver

The CC1101 component provides a driver for the Texas Instruments CC1101 Sub-1 GHz RF Transceiver (datasheet). The CC1101 is a low-cost, low-power radio chip commonly used for wireless communication in the 300-928 MHz frequency bands, including the popular 315 MHz, 433 MHz, 868 MHz, and 915 MHz ISM bands.

The CC1101 supports multiple modulation schemes (ASK/OOK, 2-FSK, 4-FSK, GFSK, MSK), configurable data rates from 600 to 500,000 baud, and adjustable output power from -30 dBm to +11 dBm. It connects to ESPHome via the SPI Bus.

The component supports two operating modes:

  • Async Mode (default): Integrates with the Remote Transmitter and Remote Receiver components for encoding and decoding RF protocols.
  • Packet Mode: Built-in packet handling with sync word detection, CRC, and the on_packet trigger. Best for FSK/GFSK modulation when communicating with other packet-based radios.
CC1101 Module

Component Configuration 

# Minimal Example
cc1101:
  cs_pin: GPIOXX
  frequency: 433.92MHz

Configuration Variables

Hardware Settings

  • cs_pin (Required, Pin): The SPI Chip Select (CSN) pin connected to the module.
  • gdo0_pin (Optional, Pin): The GDO0 pin. Required when packet_mode is enabled, also used for single pin mode switching.

General Settings

  • frequency (Optional, frequency): The operating frequency. Range: 300MHz to 928MHz. Defaults to 433.92MHz.
  • output_power (Optional, float): The transmission power in dBm. Range: -30 to 11. Defaults to 10.
  • modulation_type (Optional, enum): The modulation format. Options: ASK/OOK (default), 2-FSK, 4-FSK, GFSK, MSK.
  • symbol_rate (Optional, int): The symbol rate in Baud. Range: 600 to 500000. Defaults to 5000.
  • rx_attenuation (Optional, enum): Internal RX attenuation. Options: 0dB, 6dB, 12dB, 18dB. Defaults to 0dB.
  • dc_blocking_filter (Optional, boolean): Enable the digital DC blocking filter. Defaults to true.
  • manchester (Optional, boolean): Enable Manchester encoding. Defaults to false.

Tuner Settings

  • filter_bandwidth (Optional, frequency): The receive filter bandwidth. Range: 58kHz to 812kHz. Defaults to 203kHz.
  • fsk_deviation (Optional, frequency): Frequency deviation for FSK/GFSK modulation. Range: 1.5kHz to 381kHz.
  • msk_deviation (Optional, int): Deviation index for MSK modulation. Range: 1 to 8.
  • channel (Optional, int): Channel number (added to base frequency). Defaults to 0.
  • channel_spacing (Optional, frequency): Spacing between channels. Range: 25kHz to 405kHz. Defaults to 200kHz.
  • if_frequency (Optional, frequency): Intermediate Frequency. Range: 25kHz to 788kHz. Defaults to 153kHz.

Packet Mode Settings

These settings enable the CC1101’s built-in packet handling with FIFO buffering, sync word detection, and optional CRC checking.

  • packet_mode (Optional, boolean): Enable FIFO packet mode. When enabled, gdo0_pin is required. Defaults to false.
  • packet_length (Optional, int): Packet length in bytes. Set to 0 for variable length packets (length byte prepended to data). Range: 0 to 64. Defaults to 0.
  • crc_enable (Optional, boolean): Enable CRC-16 calculation and checking. The CC1101 uses CRC-16-IBM (polynomial 0x8005). Defaults to false.
  • whitening (Optional, boolean): Enable data whitening to improve DC balance. Defaults to false.
  • sync_mode (Optional, enum): Sync word detection mode. Options: None, 15/16, 16/16, 30/32. Defaults to 16/16.
  • sync0 (Optional, hex): Lower sync word byte. Defaults to 0x91.
  • sync1 (Optional, hex): Upper sync word byte. Defaults to 0xD3.
  • num_preamble (Optional, int): Number of preamble bytes to transmit. Range: 0 to 7 (maps to 2, 3, 4, 6, 8, 12, 16, 24 bytes). Defaults to 2 (4 bytes).

AGC (Automatic Gain Control) Settings

Advanced users can fine-tune the AGC dynamics. The AGC automatically adjusts receiver gain to handle signals of varying strength. These settings control how aggressively and quickly the gain adapts. See the CC1101 Datasheet for detailed information.

  • magn_target (Optional, dB): Target signal amplitude for the AGC loop. Higher values increase sensitivity but may cause clipping on strong signals. Range: 24dB to 42dB in increments of 3 (e.g., 33dB). Defaults to 42dB.
  • max_lna_gain (Optional, dB): Limits the maximum LNA (Low Noise Amplifier) gain. Use to prevent saturation in high-signal environments. Defaults to Default. Options: Default, 2.6dB, 6.1dB, 7.4dB, 9.2dB, 11.5dB, 14.6dB, 17.1dB.
  • max_dvga_gain (Optional, enum): Limits the maximum DVGA (Digital Variable Gain Amplifier) gain. Options: Default, -1, -2, -3. Defaults to -3.
  • lna_priority (Optional, boolean): If true, reduce LNA gain before DVGA gain when decreasing overall gain. Useful for optimizing noise figure. Defaults to false.
  • carrier_sense_above_threshold (Optional, boolean): Only accept packets when carrier sense indicates a signal is present. Defaults to false.
  • carrier_sense_abs_thr (Optional, int): Absolute RSSI threshold for carrier sense. The radio considers a carrier present when RSSI exceeds this level. Range: -8 to 7.
  • carrier_sense_rel_thr (Optional, enum): Relative RSSI threshold for carrier sense, compared to the current noise floor. Options: Default, +6dB, +10dB, +14dB.
  • filter_length_fsk_msk (Optional, enum): Averaging length for AGC in FSK/MSK modes. Longer values provide more stable gain but slower response. Options: 8, 16, 32, 64.
  • filter_length_ask_ook (Optional, enum): Averaging length for AGC in ASK/OOK modes. Longer values provide more stable gain but slower response. Options: 4dB, 8dB, 12dB, 16dB.
  • freeze (Optional, enum): Controls when AGC gain is frozen (held constant). Options: Default, On Sync, Analog Only, Analog And Digital.
  • wait_time (Optional, enum): Time to wait after a gain change before allowing another adjustment. Options: 8, 16, 24, 32. Defaults to 32.
  • hyst_level (Optional, enum): Hysteresis level to prevent gain oscillation on borderline signals. Options: None, Low, Medium, High.

Triggers

on_packet Trigger

In packet mode, this trigger fires when a packet has been received. A variable x of type std::vector<uint8_t> containing the packet data is passed to the automation. The variables rssi (signal strength in dBm) and lqi (link quality indicator, 0-127, lower is better) are also available.

cc1101:
  cs_pin: GPIOXX
  gdo0_pin: GPIOXX
  frequency: 433.92MHz
  modulation_type: GFSK
  symbol_rate: 4800
  packet_mode: true
  packet_length: 8
  on_packet:
    then:
      - lambda: |-
          ESP_LOGD("cc1101", "packet %s rssi %.1f dBm lqi %u", format_hex(x).c_str(), rssi, lqi);

Actions

cc1101.begin_tx Action

This action puts the radio into TX mode and switches gdo0_pin to output mode.

cc1101.begin_rx Action

This action puts the radio into RX mode and switches gdo0_pin to input mode.

cc1101.set_idle Action

This action puts the radio into an idle state.

cc1101.reset Action

This action resets the CC1101 chip and re-applies configuration.

cc1101.send_packet Action

This action transmits a packet. Only available when packet_mode is enabled.

Configuration variables

  • data (Required, list): The packet to send, length should match the configured packet_length.
on_...:
  - cc1101.send_packet:
      data: [0x12, 0x34, 0x56, 0x78]

Integration with Remote Receiver/Transmitter

For ASK/OOK modulation, the CC1101 integrates with Remote Receiver/Transmitter for protocol encoding and decoding. The component automatically configures the GDO pins to support both dual and single pin wiring schemes.

This is the simplest and recommended wiring scheme. It uses separate pins for transmitting and receiving data.

  • GDO0 (Module Pin 3): Connect to the MCU pin used by remote_transmitter.
  • GDO2 (Module Pin 8): Connect to the MCU pin used by remote_receiver.
cc1101:
  cs_pin: GPIOXX

remote_transmitter:
  pin: GPIOXX  # Must match GDO0
  carrier_duty_percent: 100%
  on_transmit:
    then:
      - cc1101.begin_tx
  on_complete:
    then:
      - cc1101.begin_rx

remote_receiver:
  pin: GPIOXX  # Must match GDO2
  dump: all

2. Single Pin Wiring

This wiring scheme uses a single MCU pin for both transmitting and receiving data, connected to GDO0. This requires careful configuration of the remote_transmitter and remote_receiver to avoid conflicts.

  • GDO0 (Module Pin 3): Connect to a single MCU GPIO pin.
  • GDO2 (Module Pin 8): Leave disconnected.

Single Pin with Open-Drain

ESP32 must use this method when using single-pin wiring. The shared pin should be set to open-drain with a pullup. The eot_level option (from remote_transmitter) controls the pin state after transmission completes - setting it to false keeps the pin low until explicitly released. In addition to setting the CC1101 mode in on_transmit/on_complete, the pin should be driven low before begin_tx and released before begin_rx.

cc1101:
  cs_pin: GPIOXX
  gdo0_pin: GPIOXX

remote_receiver:
  pin:
    number: GPIOXX  # Must match GDO0
    mode:
      input: true
      output: true
      pullup: true
      open_drain: true
    allow_other_uses: true
  dump: all

remote_transmitter:
  pin:
    number: GPIOXX  # Must match GDO0
    mode:
      input: true
      output: true
      pullup: true
      open_drain: true
    allow_other_uses: true
  eot_level: false
  carrier_duty_percent: 100%
  on_transmit:
    then:
      - cc1101.set_idle
      - remote_transmitter.digital_write: false
      - cc1101.begin_tx
  on_complete:
    then:
      - cc1101.set_idle
      - remote_transmitter.digital_write: true
      - cc1101.begin_rx

Single Pin with Automatic Mode Switching

When gdo0_pin is configured, begin_tx and begin_rx automatically switch the pin between output and input modes, simplifying the configuration.

cc1101:
  cs_pin: GPIOXX
  gdo0_pin: GPIOXX

remote_receiver:
  pin:
    number: GPIOXX  # Must match GDO0
    allow_other_uses: true
  dump: all

remote_transmitter:
  pin:
    number: GPIOXX  # Must match GDO0
    allow_other_uses: true
  carrier_duty_percent: 100%
  on_transmit:
    then:
      - cc1101.begin_tx
  on_complete:
    then:
      - cc1101.begin_rx

Troubleshooting

“FF0F was found” Error

If you see a log entry stating FF0F, 0000, or FFFF during setup, this indicates an SPI communication failure. Check your wiring (MISO/MOSI/CS).

No Signal During Transmit

  • Check Pinout: For all modes, the data line must be connected to GDO0 (Module Pin 3), as the CC1101 chip only supports transmission input via the GDO0 pin.
  • Check Pin Mode: Ensure gdo0_pin is configured for automatic pin mode switching.

See Also

CC1101 Low-Power Sub-1 GHz RF Transceiver

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