Re: Multiplexing LEDs - calculating resistor value

On Tue, 27 Jun 2006 23:32:21 GMT, Rich Grise <richgrise@xxxxxxxxxxx>
wrote:

On Tue, 27 Jun 2006 11:23:19 -0500, John Fields wrote:

On Tue, 27 Jun 2006 10:37:44 -0500, John Fields
<jfields@xxxxxxxxxxxxxxxxxxxxx> wrote:

Like this, actually:

+-------------------------------------------+
| 0ms |
| |<-----------2.5ms----------->| |
| ____________ ________________ |
+---->|____________|________________|--+ |
FILL ROW 1 DO OTHER STUFF | |
+--------------------------------------+ |
| |<----------2.5ms------------>| |
| ____________ ________________ |
+---->|____________|________________|---+ |
FILL ROW 2 DO OTHER STUFF | |
. |
. |
. |
| |
+---------------------------------------+ |
| 20ms |
| |<----------2.5ms------------>| |
| ____________ ________________ |
+---->|____________|________________|-------+
FILL ROW 8 DO OTHER STUFF

If the shift registers have registered outputs, i.e., if the outputs can
stay at the previous state while new data is being clocked in, and it
needs another (different) clock to transfer the new data to the output
latches, you could interleave the shifts - i.e., while row 1 is enabled
and the shift register outputs are latched, clock in row 2 data. Disable
row 1, clock the shift register output latches, and enable row 2, and so
on.

IOW, a given row wouldn't have to be blanked during the shift register
load time.

Cheers!
Rich


--
John Fields
Professional Circuit Designer
.

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