Studio Sub-GHz RF Power Control (studio_yardstick)

Production tools and firmware drivers for automated 433.92 MHz sub-GHz RF power switching in the recording studio using a Great Scott Gadgets YARD Stick One transceiver hosted on PiKVM V4 Plus (pikvm-studio).

For in-depth reverse-engineering analysis and hardware background, see the Sub-GHz RF Studio Power Automation Wiki.

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1. Hardware Specifications

• Host Controller: PiKVM V4 Plus (Raspberry Pi 4 Model B, 2GB RAM, Arch Linux ARM aarch64)
• RF Transceiver: Great Scott Gadgets YARD Stick One (1d50:605b)
• RF SoC: Texas Instruments CC1111F32 (24.0 MHz reference crystal)
• Frontend Amplifier: Skyworks SE2431L (+20 dBm TX power enabled via setAmpMode(1))
• Carrier Frequency: 433.920 MHz
• Modulation: ASK / OOK (Amplitude Shift Keying / On-Off Keying)
• Symbol Rate: 3433.22 baud (T_e = 291.27\,\mu\text{s})
• Protocol: 33-bit Princeton / Fosmon Pulse-Width Modulation (PWM)

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2. CC1111 Calibrated Register Configuration

Because the CC1111 USB SoC utilizes a 24.0 MHz crystal (unlike standalone CC1101 26.0 MHz crystals), registers must be configured with:

Register	Address	Value	Description
FREQ2	0xDF09	0x12	Frequency Synthesizer MSB: \text{FREQ} = \frac{433,920,000}{24,000,000} \times 2^{16} = \mathbf{0x121473}
FREQ1	0xDF0A	0x14	Frequency Synthesizer Middle Byte
FREQ0	0xDF0B	0x73	Frequency Synthesizer LSB
CHANNR	0xDF0C	0x00	Base channel
MDMCFG4	0xDF10	0x08	Channel bandwidth: 187.5 kHz, DRATE_E = 8
MDMCFG3	0xDF11	0x84	DRATE_M = 132 -> 3433.22 baud
MDMCFG2	0xDF12	0x30	30: ASK/OOK, no sync word / preamble
MDMCFG1	0xDF13	0x00	Zero preamble bytes
MDMCFG0	0xDF14	0xF8	Channel spacing exponent
PA_TABLE1	0xDF2F	0xC0	Maximum TX power (+10 dBm base, +20 dBm with SE2431L)
PA_TABLE0	0xDF2E	0x00	Carrier OFF (OOK low)
FREND0	0xDF17	0x01	Use PA_TABLE1 for bit 1
MCSM0	0xDF18	0x18	Auto-calibration on IDLE to TX transition
PKTCTRL0	0xDF08	0x00	Fixed packet length mode

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3. Protocol Timing & Framing Structure

• Bit 0: 1 tick High, 3 ticks Low (1000 -> 291 µs High, 874 µs Low)
• Bit 1: 3 ticks High, 1 tick Low (1110 -> 874 µs High, 291 µs Low)
• Trailing Sync: 1 tick High, 35 ticks Low (1 + 35 zeros -> 291 µs High, 10.19 ms Low)
• Frame: 33 data bits (132 ticks) + Sync (36 ticks) = 168 ticks = 21 bytes (48.93 ms)
• Burst: 30 back-to-back continuous frames = 630 bytes (~1.468 seconds)

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4. Device Payload Truth Table

Device Key	Device Name	State	33-Bit Binary Bitstream	Hex Payload
mrc	Moroccan Lamp	ON OFF	110100001100000100001011011110100 110100001100000100001010011110110	0x1a18216f4 0x1a18214f6
rack	Recording Rack	ON OFF	001011011010100100001011100110000 001011011010100100001010100110010	0x5b521730 0x5b521532
computer	Studio Computer	ON OFF	001011011010100100001101100111110 001011011010100100001100100111100	0x5b521b3e 0x5b52193c
sub	Subwoofer	ON OFF	010110100111010000001101000111000 010110100111010000001100000111010	0xb4e81a38 0xb4e8183a
pa	Main PA Speakers	ON OFF	010110100111010000001011000110100 010110100111010000001010000110110	0xb4e81634 0xb4e81436
tv	TV Monitor	ON OFF	010110100111010000001111000111100 010110100111010000001110000111110	0xb4e81e3c 0xb4e81c3e
neewer	Neewer LED Lights	ON OFF	001010010110011000001111010101110 001010010110011000001110010101100	0x52cc1eae 0x52cc1cac

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5. Repository Structure

studio_yardstick/
├── bin/
│   └── studio-power          # Production CLI tool for PiKVM (Python / rflib)
├── src/
│   ├── cc1111_rfcat.h        # Symbolic definitions for CC1111 registers & RfCat protocol
│   ├── yard_tx.c             # Standalone C libusb-1.0 direct CC1111 transmitter
│   ├── flipper_replay.c      # Standalone C Flipper Zero RAW .sub pulse replayer
│   └── Makefile              # Build rules for native C tools
├── docs/
│   └── protocol_spec.md      # Detailed 33-bit Princeton/Fosmon PWM timing specification
└── README.md                 # Technical specification and command reference

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6. Usage & Operations

Production CLI (studio-power)

The utility is permanently installed on pikvm-studio at /usr/local/bin/studio-power.

# Control individual outlets:
$ sudo studio-power mrc on
$ sudo studio-power mrc off

$ sudo studio-power rack on
$ sudo studio-power rack off

$ sudo studio-power computer on
$ sudo studio-power computer off

$ sudo studio-power sub on
$ sudo studio-power sub off

$ sudo studio-power pa on
$ sudo studio-power pa off

$ sudo studio-power tv on
$ sudo studio-power tv off

$ sudo studio-power neewer on
$ sudo studio-power neewer off

# Whole-studio session turn-up / turn-down:
$ sudo studio-power all on
$ sudo studio-power all off

# List devices:
$ studio-power list

Compiling Native C Utilities

$ cd src
$ make
$ sudo make install

Standalone C Direct Transmission (yard_tx)

# Transmit raw 33-bit code (30 repeats, Power Amplifier ON):
$ sudo yard_tx 110100001100000100001011011110100 30 1

Flipper Zero RAW Pulse Replay (flipper_replay)

# Replay captured Flipper Zero .sub file directly:
$ sudo flipper_replay Mrc_on.sub 1 30

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7. External References

• Fosmon Wireless Remote Control Transmitter (FCC ID: 2A3BM5782988)
• Great Scott Gadgets YARD Stick One Portal
• YARD Stick One Hardware Schematics & Design Files (GitHub)
• Texas Instruments CC1111F32 Sub-1 GHz SoC Datasheet