Using QEI with dsPIC30F2010

link555 · Joined: 29 Jul 2010 Posts: 14 Location: North Vancouver

When you call the setup_qei( ) routine, does it auto assign 3 pins (QEA,QEB and INDX)?

I have an encoder that does not have a Index output, I would like to use this the INDX(Pin5) on the dsPIC30F2010 for something else.

Ttelmah · Joined: 11 Mar 2010 Posts: 19518

Start by looking at the data sheet. QEA, and QEB, are required, so 'yes' these will be allocated. However the index, can be used to reset the count based on the setting in the QEIM bits. If you then look at the CCS defines for the QEI settings, you will see that QEI_RESET_WHEN_IDX_PULSE, is an option.
Obviously you have to work out your own way of resetting the counter (you can do this on a count, or from another source), but the index pin should be available if you don't select this option.

link555 · Joined: 29 Jul 2010 Posts: 14 Location: North Vancouver

Thank you, I was just wondering where in the set_up routine it sets the ADPCFG to a digital input for the index pin. My suspicion is that it sets all three as (QEA, QEB and Index) as inputs. As your advice indicates, I avoided using any references with the IDX pin, but pin 5(IDX) still got affected. I have a LCD being driven from that pin....

Thank you for your input.

Ttelmah · Joined: 11 Mar 2010 Posts: 19518

I've never had any problem, but on a port used for something like QEI, I'd generally use 'FAST_IO', and make sure I have setup the TRIS myself. I'd suggest you do this.

link555 · Joined: 29 Jul 2010 Posts: 14 Location: North Vancouver

I will do that. thanks again.

link555 · Joined: 29 Jul 2010 Posts: 14 Location: North Vancouver

I checked I used fixed I/o...no dice.....so I moved the LCD off of that Idx pin for now. Otherwise the qei function works great.

Ttelmah · Joined: 11 Mar 2010 Posts: 19518

FIXED_IO, is _not_ the same as FAST_IO.

With FIXED_IO, though you specify the I/O you want, the compiler will still set the TRIS on every I/O occasion, and will override this with it's own settings. With FAST_IO, no compiler overriding is done, and it becomes your responsibility to set everything.

Tell us your compiler version?. I'll check what your compiler does for the index pin on your version.

Ttelmah · Joined: 11 Mar 2010 Posts: 19518

Just tested on a PIC30F3011 (nearest chip I have to yours), and I can merrily output to the INDX pin.

Was running: