I2C on a 14M

[Andrew Cowan]

I'm upgrading a circuit board which used to talk to an ultrasonic range finder (via pulse widths). However, I have upgraded to using an SRF235, which uses I2C. It has four registers, one to write to, and two two read. The other is unused.

However, my circuit board has 5 other PICAXEs on, and I am reluctant to redesign it to use an X/X1/X2 chip, so I am investigating the possibility of bit-banging I2C.

The current setup:
The two pins connected to the range finder are leg 5 and leg 9 (in 2 and out 4).

I have had a look for hippy's code for I2C on an 08M, but I couldn't find it. Is it possible to bit bang this code on a 14M? If I run out of space/cannot use these pins, I will upgrade to a 20X2, but due to the lack of room on the board, I will need to amuputate the bottom 6 legs and still bit bang the protocol.

Is it possible on a 14M?

Thanks

Andrew

 

[Technical]

Peter Anderson has some sample bit busted i2c routines e.g.

http://www.phanderson.com/picaxe/max518.html

The pins you have used are bidirectional via 'portc' (portc 1 and 5 - Appendix C in manual part 1) and so with a bit of work this would be possible.

 

[hippy]

Not sure where my earlier I2C code for 08M is but here's one version attached. It does soft-control of the I2C bus ( only ever output low or input to achieve a high on the bus ) which is what would be recommended.

 

[Andrew Cowan]

Many thanks for that, hippy. I'll let you know how I get on.

Andrew

 

[MPep]

Look at Buzby's response in this thread.
@Hippy,
I believe this is your code example here. http://www.picaxeforum.co.uk/showthread.php?t=15496

 

[kd5crs]

You've probably thought of this, but you could always make a 20x2 daughterboard that sits above the main board (and any space limitations). The daughterboard would route the 20x2 pins where you need them in the 14 pin footprint, leaving off 6 unused pins on the 20x2.

I've been cramming a lot of stuff into window blinds, which forces me to think 3D.

Brian