[Arm-netbook] IC for analog and digital buttons (EOMA-68)

[Luke Kenneth Casson Leighton]

On Thu, Aug 7, 2014 at 7:55 AM, Luke Kenneth Casson Leighton
<lkcl at lkcl.net> wrote:
> On Wed, Aug 6, 2014 at 6:10 PM, Daniel Iglesias
> <daniel.iglesias at gmail.com> wrote:
>> 06/08/14 14:18, Luke Kenneth Casson Leighton wrote:
>>>
>>> On Wed, Aug 6, 2014 at 1:19 PM, Miguel Garcia <gacuest at gmail.com> wrote:
>>>
>>>
>>>> A basic sketch of the block diagram:
>>>> http://oi57.tinypic.com/16aeffb.jpg
>>>
>>>   ok great.
>>>
>>>   so, things that are missing from the diagram:
>>>
>>>   * digital GPIO IC connects its IRQ-OUT to EINT0-IN on EOMA68
>>
>> What's the purpose of this IRQ line? After looking at the GPIO IC datasheet
>> I'm assuming it's there so the IC is polled only when the inputs change, is
>> this correct? (i.e., avoiding busy-waiting)
>
>  http://www.nxp.com/products/interface_and_connectivity/i2c/i2c_general_purpose_i_o/series/PCA9575.html
>
>  you _want_ one that has an IRQ.  don't use one that doesn't.

 ...except do try to find one that's a bit less than $0.95 in volume!!
http://www.futureelectronics.com/en/technologies/semiconductors/comm-products/i2c/Pages/4007443-PCA9575PW2,118.aspx?IM=0