Can PBP read optical encoder damn fast? :)

[Ioannis]

This is simple 3 pin incremental encoder, middle pin is tied to VCC, A and B are tied to PORTB.3 PORTB.4, which are also pull down with 10K resistors. If I rotate shaft slowly, then no false readings. What can be reason, some wiring issue or code inefficiency?

Well, your LCD may be slowing down the response. And since you use PAUSE and LCDOUT it is expected that program is not the most efficient. The encoder is best done in ISR and even better using hardware module when available.

Ioannis

[CuriousOne]

I don't see how to avoid use of pause statement. We have time changing, things are happening within time, so how not to consider time? In final device, there will be no LCDOUT, if that is the problem.

[Ioannis]

ISR then.

Ioannis

[HenrikOlsson]

If the encoder strip has 60 lines per cm then you can get a resolution of 240 counts per cm by counting all four edges of the quadrature cycle.

If you're OK with 60 it makes it a lot easier (compared to 4x decoding) since, again, all you need to do is poll channel B on the rising edge of channel A and you have your count direction. Using a coupe of external NAND gates (or perhaps the CLC module if your PIC has one) you can decode that into two discrete signals, up & down. Feed those into two counters on they'll count for you while you PAUSE.

If counting with software, polling the inputs, then using PAUSE, LCDOUT or any other command that takes longer to execute than the shortest time between two pulses WILL ruin the day - in which case resorting to interrupts or hardware counter is the only way. This is why I asked if the the counting should go on WHILE outputting to the DDS.

/Henrik.

[CuriousOne]

As said above, there will be no LCDOUT or any other statements in the loop, except DDS updating. Regarding the precision, have not decided it yet, because have not build and have not heard maybe 10 readings per CM also will be ok....

[CuriousOne]

I've found this: https://hackaday.io/project/122039-i2c-encoder-v2 - Ready firmware for the above mentioned PIC with I2C output. So what if I use this chip with that firmware to get data from encoder, and then use my PIC to send required data to DDS?

[Ioannis]

If I get it right, you will use a PIC to read a quadrature encoder, then communicate with I2C to another PIC and the second PIC will send the data to your DDS?

Does this sound logical and efficient?

You have a PIC then just do it! Use some lines in ISR and get the job done.

After all, it is a good programming exercise! And the bonus is that you will be thrilled when finished! Don't be afraid of the ISR. A bit of work but you can do it!

Ioannis

P.S. what is your current PIC?