Fig.: SimNet connection technology
SimNet is a bus system for boats from Simrad, which is based on the CAN bus and has limited compatibility with NMEA2000, comparable to Raymarine's SeaTalk NG. With SimNet, Simrad also relies on proprietary connection technology that is only compatible with Simrad products. Physically, 5-pin connectors are used as in NMEA2000, but in a different format. The disadvantage, however, is the high price for the proprietary connection technology. However, adapters to NMEA2000 are also available.
Benefits of SimNet:
- Higher data rates: At 250 kBit/s, SimNet has significantly higher data rates than NMEA0183.
- Bi-directional transmission: SimNet is based on the CAN bus and offers bi-directional transmission so that data can be sent as well as received.
- Reliability: SimNet is a reliable network protocol that guarantees that data is transmitted correctly. To do this, checksums are used for the telegrams and faulty telegrams are resent.
- Easy Wiring: Devices easily plug into a SimNet bus using proprietary connectors. This minimizes wiring errors.
Disadvantages of SimNet:
- Proprietary: SimNet uses a proprietary protocol in some parts, but is also compatible with NMEA2000 to a limited extent.
- Expensive connection technology: SimNet uses its own proprietary connector format, which is quite expensive and cannot be replaced by other connectors. However, other connector formats such as NMEA2000 are also supported via adapters.
- Lack of extensibility: SimNet cannot be expanded with new data content or data formats. The data transmission is designed purely for sensor data. Image data or other large amounts of data cannot be transmitted via SimNet.
Overall, SimNet offers similar performance to NMEA2000. Proprietary extensions to the protocol integrate Simrad's in-house products better into SimNet than would be possible with NMEA2000. SimNet has proven itself in many boats and is considered a reliable bus system, but it also comes at a price.
There is no separate open source implementation for SimNet that supports the special features of SimNet. Rather, with the Open source implementation to NMEA2000 by Timo Lappalainen part of SimNet can be used, provided it is compatible with NMEA2000.