VSM and i2c: Beware

Why are companies so reluctant to tell you what their products won't do?


The Picaxe VSM simulator is a great product if it simulates the functions that you want to use. The problem is that it is sold by Revolution Education with broad claims - ie that it will do simulation "for all M, X, X1, X2 PICAXE chips" and "Support for all major protocols, including RS232, spi, i2c, 1-wire, etc."


But - after investing five or six hours learning my way around VSM (which provides reasonable-but-not-brilliant documentation and limited tutorials, but still involves a big learning curve) - I hit problems with an i2c interaction between two 20x2 Picaxe chips not working as I expected.


So I reduced everything to the absolute basic, with one chip acting as Master, trying to update a single byte on the other, set up as Slave.


It failed - and there in the log (as an item of Information, not an Error) was the message:
Background i2c receive (slave mode) cannot be simulated


I've googled for workarounds or updates - and there are none. So everything points to this being a fundamental limitation of the VSM simulation program as supplied by Revolution Education.


I don't expect the world for sixpence - but I do think it would be rather more grown-up for companies selling products that have known limitations to treat their potential customers like adults and say "This product does all these brilliant things, but please be aware before you buy it that it won't do the following".


UPDATE 23 April 2012


Reply from Picaxe Technical Support:


The current PICAXE X2 VSM models have only been recently added, are in beta state and therefore don't support all that a physical PICAXE may offer; I2C master mode is supported but I2C slave mode currently is not. I2C slave emulation is quite complicated (effectively a whole different model to layer on top) and we do not currently have an estimate as to when that may be supported.