@Laser_Developer wrote:
We're designing a laser altimeter for small drones and we want to make sure that the configuration is suitable for both the drone manufacturers and DIY'ers. The laser module will be offered in two formats, either a complete unit with Aluminum closure that can be added to an existing drone or in an open frame format for the OEM market. It will come with a serial port interface.
The question that I'd like to pose to this forum is whether or not we should include an I2C interface. I know that I2C is popular but I cannot find any technical justification for using this protocol between a flight controller and an external device. NXP (formally Philips) who define the I2C standard make it very clear that it is designed for use on a circuit board where things like the trace capacitance and terminating impedance can be accurately controlled.
Using the I2C protocol through a cable and connectors can result in unreliable behavior, something that gets worse if the terminating resistors are not accurately matched to the cable and if the cable itself has high capacitance. The speed of the communication is compromised by the cable length and may drop below the 100k bits per second that is the typical "slow" specification.
Of course, special drivers and error checking can be added but this is something that the average enthusiastic hobby drone maker is unlikely to consider when building their own drone.
Despite these misgivings, we are prepared to offer the I2C as an optional interface but we would not be able to guarantee its performance. This worries me greatly because I don't want to make unreliable equipment. Also, when ordering the product in its closed format, only one protocol would be available so you couldn't buy an I2C unit then change it over to serial later if it doesn't work.
I'd love to hear your thoughts
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