writeI2cBlockSync returns a PromisifiedBus rather than the suggested number of bytes written

[reesesm2000]

Calling writeI2cBlockSync correctly writes data to the device but rather than returning what I assume should be the length written (based on VS intellisense saying the function returns a number), it returns a PromisifiedBus object. What should be returned by this function?

[fivdi]

The documentation for writeI2cBlockSync can be found here. The documentation doesn't mention a return value so it should be assumed there is none. writeI2cBlockSync doesn't have a documented return value as the C function that ends up being called by writeI2cBlockSync doesn't document it's return value either. If writeI2cBlockSync fails, an error will be thrown.

In reality, as can be seen here, writeI2cBlockSync returns the bus object that it was called on. Note that this is undocumented and shouldn't be relied on. You mention above that when you call writeI2cBlockSync, a PromisifiedBus is returned which implies that your program is using a PromisifiedBus. The documentation for PromisifiedBus can be found here and as can be seen, it is not documented that it supports method writeI2cBlockSync.

I hope this answers your question.

[reesesm2000]

Thanks for the super quick response! Thanks for the explanation. I had just assumed (which I hate doing lol) that since VS intellisense was showing a number being returned, it would most likely be the length. Below is a screenshot of what it shows. I will close this now.

[fivdi]

I see you are using TypeScript. The type definitions for i2c-bus don't appear to be 100% correct, for example, writeI2cBlockSync is defined like this and the definition specifies that the number of bytes written is returned as a number which is incorrect.

[reesesm2000]

Yeah, forgot to mention that. So writeI2cBlockSync should probably return void like writeI2cBlock does.

[fivdi]

Yes, returning void would be correct.