Another nail in the Picaxe sensor's coffin...

More work done on migrating the circuits to Pic this weekend in between watching the Rugby World cup and Ghostbusters 35th anniversary…

 

I was originally planning on having pic and picaxe development running concurrently and releasing both open source as Picaxe use Basic.

However a snag has been found.

 

Picaxe has two commands for dealing with reading serial data SERIN and HSERIN. SERIN enables serial communication on pretty much any pin. HSERIN uses the hardware of the underlying pic. There is a difference between the two – Over the weekend, I was working on constructing the signal – having got the baud rates set and the timings sorted down to the millisecond (Well… nanosecond pretty much) The Legacy side of the hit works fine. The problem is the SEROUT/SERIN command for output/input – the actual length of time it takes to send the serial data is longer than the equivalent from the Pic, or from HSEROUT.

This in itself isn’t too much of a problem, apart from when it comes to reading the signal. SEROUT creates a much longer serial code than the hardware equivalent. Meaning that a sensor as they currently stand, cannot read the serial data part of the signal if it has been generated by a PIC. I think this can be mitigated by changing from SEROUT/SERIN to HSEROUT/HSERIN to use the underlying pic hardware.

 

But, given the other limitations of the Picaxe based sensors, I just cannot be bothered to faff around with something that I already know won’t be able to handle everything I want it to.

Changing the Picaxe based sensors to Pic is straight forward enough – I’ve got to reprogram the chips back to their underlying pic chip (Programming a Picaxe as the underlying Pic removes the Picaxe bootstrap/compiler from the chip) swap two pins around on the hardware – which should be basically move 1 wire and 1 resistor – all it’ll cost is 1 resistor unless I get lucky with the leg length, but that’s not really an issue to worry about.

 

It is essentially another nail in the coffin of the advanced Picxe based sensors 😊

 

The whole project would be even easier if I wasn’t also trying to make sure that Legacy WoW kit worked with it as well, as in that case I’d change the signal to a relatively straight forward serial data stream and get rid of the 1800hz 50ms hit frequency. BUT I am, so I’m not 😊 )