WSAL23652 – TTL TO RS422 (B)/en
Documentation notice: This technical documentation was independently rewritten from an archived supplier source. Check technical details and commands against the product version and manufacturer documentation before use.
Summary
The Waveshare TTL TO RS422 (B) is an industrial rail-mounted converter that converts TTL signals into balanced differential RS422 signals. It supports full-duplex communication and provides galvanic isolation, surge protection, as well as TVS and ESD protection.
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Technical overview
- Compatible with the TTL/RS485 standard; converts TTL into a balanced differential RS422 signal and supports full-duplex communication.
- Supports TTL signal levels from 3.3 V to 5 V; the power supply includes reverse-protection and over-voltage circuitry.
- Onboard unibody power-supply isolation delivers stable isolated voltage without requiring an additional external power source for the isolated terminal.
- Onboard unibody digital isolation enables signal isolation with high reliability, strong anti-interference, and low power consumption.
- Onboard TVS (Transient Voltage Suppressor) effectively suppresses surge voltages and transient spikes in the circuit and provides electrostatic discharge (ESD) protection.
- Onboard resettable fuse and protection diodes ensure stable current/voltage outputs, provide over-current/over-voltage protection, and improve shock resistance.
- Connections: TTL side uses screw terminals; RS422 side also uses screw terminals with built-in 120 Ω termination resistors that can be enabled or disabled via jumpers inside the case.
- Transmission distance: TTL under 10 m; RS422 approximately 1200 m; point-to-multipoint operation supports up to 32 nodes (adding relays is recommended beyond 16 nodes).
- Enclosure: Industrial ABS housing designed for a 35 mm DIN rail, dimensions 91.6 × 58.7 × 23.3 mm.
- Operating temperature range: −15 °C to 70 °C; tested at 921600 baud and operates stably; power consumption at 5 V is 0.12 W.
Notes and version constraints
- The product is primarily designed for RS422 devices; using it with RS485 devices is only possible in transmit mode – the TTL TO RS485 (B) model is recommended instead.
- For short-distance communication, the built-in 120 Ω termination resistors can be disabled by setting the jumpers to NC; for long-distance multi-device setups, 120 Ω resistors should be added at the first and last devices on the bus.
- The module only provides a physical-layer hardware converter; parameters such as baud rate or node configuration do not need to be set. Modbus communication must be implemented at the protocol layer.
- Testing requires a USB-to-TTL adapter and a USB-to-RS422/RS485 adapter, which are not included in the delivery scope.
- The exact position and handling of the jumpers for the 120 Ω resistors requires opening the case; detailed steps are missing from the source and require manual verification.
Source and revision record
- TTL TO RS422 (B) - Waveshare Wiki
- Source revision: 91424
- Captured: 2026-09-04T03:12:44+00:00
- SHA-256:
0f29b40d159ba2714ef4f6a3aeae18830b5824ac2b4cc13a72664fac2a54c03b