Choosing an OBD Interface
There are many different kinds of OBD interfaces, but they can be broken down into three general categories: off-the-shelf interfaces, OBD modules, and OBD ICs (chips). To choose the right OBD interface for your application, you must consider a number of factors, including:
- Time to market
- Supported OBD protocols
- Physical size/form factor
- Connection type: USB, RS232, WiFi, Bluetooth, UART, etc
- Special features: upgradeable firmware, low current mode, enhanced commands
It is important to remember that there is almost always a trade-off between features, cost, and time to market. Your job is to find the right balance of the three competing requirements for your application, keeping in mind that sometimes the best long-term solution is different from the best short-term solution.
For example, suppose that you are given the task of designing a small, low-cost OBD-enabled device, with the goal of fielding ten units for a pilot rollout within four weeks. The best short-term solution may be to use an OBD module, which would allow you to concentrate on the design of your device and build the prototypes in time for the pilot. To reduce the cost per unit, you may later incorporate the OBD functionality in your design, using an OBD chip and discrete components.
The following sections give descriptions for each of the three categories of OBD interfaces, and list their advantages and drawbacks.
Off-the-shelf OBD interfaces do not require any additional hardware to work, and are ideal for applications that require fast time to market, and for proof-of-concept testing. They are a popular choice for OBD software developers and vehicle fleets. Many standard connection options are available including USB, RS232, WiFi, and Bluetooth.
- Complete hardware solution
- Shortest time to market
- Excellent price/performance ratio
- Hardware is fixed
- Form factor may not be appropriate in some situations
OBD modules serve as a bridge between OTS interfaces and OBD ICs. Each module includes all necessary OBD transceivers on-board, taking away the need to design and debug OBD transceivers. Their small size makes them great candidates for low-volume OBD projects with tight deadlines.
- Small form factor
- Proven design
- Reduced time to market
- Relatively expensive for high volume runs
OBD ICs (“chips”) are the best solution for high-volume projects where low cost and small PCB footprint are the top priorities.
- Lowest cost per unit
- Add only the features you need
- Most flexible solution
- High design overhead
- Longest time to market
Selecting the right OBD interface is a fine balancing act involving many engineering and economic trade-offs. Choose one that has the right mix of features, cost, and time to market for your application.