The bit stuffing mechanism adopted in controller area networks leads to unwanted jitter on frame reception times, which worsens timing accuracy, even if countermeasures are adopted to avoid contentions on the bus. Several solutions have been proposed so far for dealing with stuff bits in the payload of messages, but they are not effective for the cyclic redundancy check. In this paper, a mechanism is presented that prevents the occurrence of stuff bits in the whole frame completely. It makes the duration of frame transmissions fixed and, hence, it achieves very accurate reception times. An optimized codec has been implemented to demonstrate that this approach is feasible and can be profitably adopted in low-cost networked embedded systems with demanding timing constraints.