Mcp23s17

[Sterngleiter]

Hello, I would like to use interrupt outputs. Everything is running fine but I would like to interrogate inputs at interrupt instead of cyclic. I did not understand anything in the instructions. Has any experience that could give me tips ?
greeting

[temtronic]

When posting questions like this, please add a 'link' to the device.
OK, I downloaded the datasheet and it's a 2 port, I2C expander.
It's actually quite powerful, with YOU in charge of which pins cause an interrupt. You simply have to send that data to the device as well as active high or active low that 'triggers' the interrupt. Also you need to decide what kind of interrupt - open drain (where several devices are on the same INT bus) or discrete (1 device = 1 INT pin).
It may be that CCS has an example but it's not in my old version of the compiler.
I can't cut code and say 'here it is', as I need to have the hardware to confirm my code works.

Jay

[Ttelmah]

There is a standard driver for this with the compiler.
Has been for about 10 years!.
It allows you to write and read the individual registers. However interrupt use requires you to setup the patterns for this.

The big question is what type of interrupt is wanted?

You can have a single interrupt output from each bank, or a combined output from both. This can be active high, low or open collector.
You can set each pin to interrupt on change, or when they differ from a defined level.
Obviously when this trigger the PIC interrupt handler would have to read the port, or it can read what pattern was on the port when the interrupt fired (this is stored for you).

[Sterngleiter]

It should be a normal interrupt. If the state of a port changes then it should give me a high or low signal so I can query on spi which of the inputs has triggered, or is there another alternative? Constantly polling would only be time consuming, I think. It is said register Gpinten enables the interrupt. I do not understand what that has with Defval and Intcon register on it.
Greeting

[Ttelmah]

OK.

GPINTEN, is like the TRIS. You put into it a pattern of bits, with a '1' for every input you want to have an interrupt on. So if you want to use the interrupt on pins A0 and A1, you load GPINTENA with 0x03.

For a standard interrupt on change, you can then leave INTCONA and B both set as 0.

If you then leave MIRROR, ODR and INTPOL all set as 0, you will get the INTA output dropping when the selected pins change.

When this triggers:

You can read the INTFA register which will tell you which bit(s) have triggered.
The INTCAP register will hold a copy of the complete port at the moment the interrupt triggered.

Reading the port, will clear the interrupt.

[Sterngleiter]

Thank you for the tip. I was already on the right track. My biggest mistake was that I forgot a LOW-signal during initialization of SPI because of this written in total other registers. Without your tip, I would not have got further.