[Soekris] LED controller
petedao at gmail.com
Thu Aug 12 13:09:37 UTC 2010
Thank you so much for all your kind suggestion.
I am trying to use 74HC595. I would like to use the serial port to
control this IC, is it doable?
How can I use the serial port to provide the 595 IC with Latch, CLK,
and Serial-data-in signal or should I use 3 serial port to provide
these signals individually?
Any suggestion will be greatly appreciated.
On Tue, Aug 10, 2010 at 2:14 AM, Bernd Walter <ticso at cicely7.cicely.de> wrote:
> On Sun, Aug 08, 2010 at 05:09:26PM +0800, Pete Kay wrote:
>> Thank you for your suggestion. I have got a few 74HC595 ICs and I
>> would like to try to use GPIO to drive this IC which will then in
>> light up the LED.
>> Does anyone know how to use GPIO to generate the CLK signal? I know
>> 74HC595 needs CLK, Latch, and Data-in. Where can I find any tutorial
>> on how to use 3 GPIO pins to drive this IC? How do I synchronize
>> these three signals? Please forgive my newbie questions as I am just
>> beginning to learn about gpio.
> This signal is named clock because when used in e.g. a state machine
> you connect it to the system clock, but if you see the device alone you
> just need a signal change for data takeover and not a periodic clock.
> Setup data and latch signals, then toggle clock down and up again and
> you are done.
> You can also consider using an I2C chip, such as a PCA9555 or MCP23016,
> which are happy with 3.3V - the MCP is also available in DIP housing.
> NXP also has some I2C 16x 20mA LED driver with and without bright control,
> but for signal LEDs you rarely need 20mA.
> Another option might be to connect a microcontroller.
> There are many with I2C or USB, but unlike the last option they need
> programming first which may or may not be within your skills.
>> Any help or hint or pointer will be greatly appreciated.
>> On Sat, Aug 7, 2010 at 3:27 PM, Alvar Kusma <alvar at raamat.polva.ee> wrote:
>> > Pete Kay kirjutas:
>> >> I am trying to have my Soekris board to somehow control a set of 16
>> >> LEDs,
>> >> What are the components that I can purchase
>> >> off-the-shelf for this kind of thing?
>> > Net5501 has 12 general purpose IO pins on JP5, which are accessible from
>> > userspace. But if you need more than that, then use PIPO register like two
>> > 74573-s latches, connected to GPIO pins (if i remember correctly, then
>> > PC87366 is 5V tolerant). Software then is a bit more complicated, but not
>> > much.
>> > Another way is to use SIPO registers. For realization example see
>> > http://www.arduino.cc/en/Tutorial/ShiftOut
>> > Simplest way of course is to try directly with existing GPIO-s, but this
>> > limits LED count to 12.
> B.Walter <bernd at bwct.de> http://www.bwct.de
> Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.
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