- **Trav'ler Pro `odu` command:** The Pro's IDU has its own MCU. You must first tunnel to the ODU with `odu` before entering the motor submenu. The regular Trav'ler's IDU is a dumb RS-485 passthrough.
- **Carryout uses `g` not `a`:** The Carryout has no individual motor addressing. It uses `target` to enter targeting mode, then `g <az> <el>` for combined moves. It also can't query its initial position.
- **Carryout has no limit switches:** Uses motor stalling to detect mechanical boundaries (audible grinding).
- **Pro has the same leap-frog bug** as the regular Trav'ler (copy-pasted).
- **Carryout G2 uses `a` not `g`:** Unlike the 2003 Carryout, the G2 uses standard `a <id> <deg>` motor addressing and the `mot` submenu — protocol-compatible with the Trav'ler family.
- **Carryout G2 is RS-422 full-duplex:** Separate TX/RX pairs at 115200 baud via RJ-12 6P6C, vs. RS-485 half-duplex at 57600 on the Trav'ler variants. Requires a USB-to-RS422 converter (5V TTL).
- **Carryout G2 has `h <id>` homing:** Explicit motor home-to-reference command. Not documented on other variants.
- **Carryout G2 has DVB/RSSI:** Signal strength measurement via `dvb` submenu (`lnbdc odu` to enable LNA, `rssi <n>` to sample). Used for sky scanning / RF imaging.
The Winegard variants use two different differential signaling standards. Understanding which one matters for choosing the right USB adapter.
**RS-485 half-duplex (2-wire):** One shared differential pair carries both TX and RX. Only one device talks at a time — the transmitter drives the bus, then releases it so the other side can respond. This is how the Trav'ler IDU communicates with the ODU: the IDU sends a command on the shared T/R pair, then listens for the response on the same wires. Simple wiring (2 signal wires + ground), but throughput is limited by the turn-around time between send and receive.
**RS-422 full-duplex (4-wire):** Two separate differential pairs — one dedicated TX pair and one dedicated RX pair. Both sides can transmit simultaneously because the signals don't share wires. Higher throughput (no bus turnaround penalty), and the Carryout G2 uses this at 115200 baud. Point-to-point only (one transmitter per pair).
**RS-485 full-duplex (4-wire):** Electrically identical to RS-422 wiring (same 4-wire differential pairs), but the RS-485 spec allows multiple transmitters on each pair (multi-drop bus). For our point-to-point dish↔computer connection, 4-wire RS-485 and RS-422 are interchangeable.
**Practical consequence for this project:** The Trav'ler's RJ-25 connector exposes **both** a half-duplex pair (pins 2-3, labeled T/R) **and** a dedicated receive pair (pins 4-5, labeled RXD). Gabe's code uses only the half-duplex pair via an RS-485 adapter. Davidson's G2 code uses all four wires as RS-422. The same physical connector may support both modes depending on the firmware — this is unconfirmed on the Trav'ler but worth testing if you have a 4-wire adapter available.
### Serial Connector Pinout
The physical connector is an RJ-25 (6P6C) on the Trav'ler or RJ-12 (6P6C) on the G2 — same form factor, same 6-pin modular jack.
The DIYables RS422-to-TTL module uses the **MAX490** transceiver chip (2.5 Mbps max, well above our 115200 baud). Key specs:
- 5V TTL logic on the microcontroller side (RXD/TXD)
- 15 kV ESD protection on RS-422 lines
- TVS diode for lightning/spike suppression
- 10 ohm current-limiting resistors for overcurrent protection
- Built-in 120 ohm termination resistor (reduces echo on long runs)
- Power + TX/RX activity LEDs
- Board size: 5.0cm x 2.7cm
**Failsafe concern:** The MAX490 does not have failsafe logic, and the module has no provisions for passive failsafe bias resistors. When the RS-422 bus tri-states (no driver active — e.g., between commands, during power transitions, or if the dish firmware is slow to respond), the receiver inputs float and may see random transitions interpreted as garbage data. This can cause spurious bytes in the serial stream.
Workaround options:
1.**Add external bias resistors** — pull A/RX+ toward V+ and B/RX- toward GND through ~560 ohm resistors. This biases the idle bus to a known logic-high state (RS-422 "mark" / idle). Solder to the module or add inline on the RJ-12 breakout.
2.**Use the prompt-terminated read strategy** — our `CarryoutG2Protocol._send()` reads until `>` (ASCII 62) which naturally filters out garbage between commands, since random transitions are unlikely to produce a valid `>` in context.
3.**Ignore idle noise in firmware** — the Winegard firmware likely ignores unexpected input while it's processing or idle, but any bytes received during the bus float could corrupt the next valid command if they land in the UART buffer at the wrong time.
For short cable runs (under ~3m between ESP32 and dish), the built-in 120 ohm termination is sufficient and bus float is less likely to cause issues. For longer runs or electrically noisy environments (near motors, power supplies), add the bias resistors.
120VAC input to RP-SK87 power supply, outputs 12VDC to IDU. Internal coax carries 12-18VDC bias for LNB — do not connect 5V equipment (SDR LNAs, etc.) without bypassing the power injector.
### Physical Setup
- Base marked with arrows and "BACK" at 0/360 deg (North)
- Align "BACK" with true North for accurate tracking
- Gpredict rotor config: 127.0.0.1:4533, 0->180->360 mode, min EL 15, max EL 90
- No obstructions taller than 8" within 32.5" of base center
### Calibration
On power-up, the dish performs calibration movements to establish position and cable wrap limits (~10-15 minutes on Carryout, shorter on Trav'ler). After calibration, firmware automatically starts a TV satellite search — the init sequence kills this.
- **Leap-frog elevation bug:** original `travler_rotor.py` lines 98-105 modify `target_az` instead of `target_el`. Fixed in `leapfrog.py`. Present in both Trav'ler and Trav'ler Pro repos. See `docs/bugs.md`.
