MAX7219 controlling 2 7-segment display ! help !

Paul__B: Total and complete nonsense!

Yep, I had to draw out the array before I figured that out. If you read my last post, I corrected my self. Thanks for checking Dwight

I don’t know, I think the scan register may still come into play:

Scan-Limit Register
The scan-limit register sets how many digits are displayed,
from 1 to 8. They are displayed in a multiplexed
manner with a typical display scan rate of 800Hz with 8
digits displayed. If fewer digits are displayed, the scan
rate is 8fOSC/N, where N is the number of digits
scanned. Since the number of scanned digits affects
the display brightness, the scan-limit register should
not be used to blank portions of the display (such as
leading zero suppression). Table 8 lists the scan-limit
register format.
If the scan-limit register is set for three digits or less,
individual digit drivers will dissipate excessive amounts
of power. Consequently, the value of the RSET resistor
must be adjusted according to the number of digits displayed,
to limit individual digit driver power dissipation.
Table 9 lists the number of digits displayed and the
corresponding maximum recommended segment current
when the digit drivers are used.

I’ve only driven digits as common cathode tho, and made my own font array when I did this 8x32 display:

Looks a lot brighter in person, haven’t got filming LEDs down yet.

CrossRoads: I don't know, I think the scan register may still come into play

No.

The scan-limit register sets how many digits are displayed, from 1 to 8.

So if you have swapped digits for segments, the scan register defines how many segments you may connect - which is clearly either seven or eight.

the scan register defines how many segments you may connect

Disagree - there is no register setting to use Common Anode vs Common Cathode, so all 8 segments will always be driven - but not all 8 digits (anodes) unless the scan register is set to 8.

What he is saying is that if using digits to run segments, that register controls the number of segments since the segments are wired to the chips digit drivers. Yes, there is not common cathode/anode switch ( although there should have been ). There is a switch so that one can treat the array as 64 individual LEDs. That means, with the right data, it can be used as either cathode/anode. Dwight

http://forum.arduino.cc/index.php?topic=121174.0

[quote author=Runaway Pancake link=msg=2424009 date=1444045100] http://forum.arduino.cc/index.php?topic=121174.0 [/quote]

seems interesting but there is a problem with the links when you share it it opens in new tab with this : http://"http//forum.arduino.cc/index.php?topic=121174.0%22

(Offtopic - Pasting in links seems to vary day by day as well - I often see extra http & %22 added, but some days not - links I have created today typing in [ url ] and [ /url ] are working, but I have not tried any forum links today. Forum link pasting yesterday with Chrome seemed to work ok. Very aggravating at times.)

I don't know why that happens either. Clicked on the 'View source' button and fixed the hyperlink. [ If typed in as it is/was shown, that works (of course). ]

I always cut and paste links anyway for security reasons. I want to know where I'm connecting if possible. Dwight

CrossRoads: Disagree - there is no register setting to use Common Anode vs Common Cathode

And that is precisely the point.

In fact, the chip does not actually have "segment drivers" or "digit drivers" at all notwithstanding what they are called in the datasheet - it has anode drivers and cathode drivers with each cathode driver corresponding to one register in the chip, and the "Scan limit" register determining how many cathode drivers are enabled. It does not care to what you actually connect the lines as long as they connect correctly to anodes and cathodes in a matrix.

CrossRoads: so all 8 segments will always be driven - but not all 8 digits (anodes) unless the Scan Limit register is set to 8.

So if we now understand that the cathode drivers are now connected to segments in a common anode display, then the Scan Limit register will necessarily determine how many segments are enabled in the multiplex.

i am use max 7219 ic with single digit 7 segument Display use college project ,

and "led control.h" header i was use but its not show properly plz help me friends