[minima] Re: band switching
- From: Thomas Sarlandie <thomas@xxxxxxxxxxxxx>
- To: "minima@xxxxxxxxxxxxx" <minima@xxxxxxxxxxxxx>
- Date: Tue, 11 Feb 2014 01:19:12 -0800
Dave,
I was not sure but it looks like the pcf8574 would work in 3.3v:
http://www.nxp.com/documents/data_sheet/PCF8574.pdf
I vote for this option. Using the i2c bus is very elegant in my opinion.
The chip is a little more expensive though (30 to 80 cents on ebay from
chinese vendor and in qty of 10).
thomas
On Sun, Feb 9, 2014 at 2:58 PM, Dave <dave@xxxxxxxxxx> wrote:
> Steve:
> Of course if you use a I2C expander such as the PCF8574, you use 0
> additional I/O lines. It connects to the I2C in parallel with the Si570.
>
> Dave - WB6DHW
> <http://wb6dhw.com>
>
>
> On 2/9/2014 2:43 PM, Steve VK2SJA wrote:
>
>>
>> Steve, this uses just two lines.
>>>
>> Alright. I'll admit it. This muddle headed wombat is still very confused.
>>
>> 1 x Pin to pulse counter in 4017 decade counter to select band pass filter
>> +1 x Pin to reset 4017 decade counter to default known start state
>>
>> = 2 pins
>>
>> 2 pins + 1 pin for controlling the low pass filter selection = 3 pins.
>>
>> vs
>>
>> 3 pins Binary Coded Decimal (BCD) to control *both* low pass filter
>> selection and the output band pass filter selection.
>>
>> Two different ways to arrive at the same level of control. But is it not
>> still 3 pins = 3 pins?
>>
>> So where are we saving an IO line?
>>
>> I'm probably being completely daft and missing the flaming obvious but I
>> just can't see it.
>>
>> Help!
>>
>> 73, Steve.
>>
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