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i am wondering how the MAX7219 in a LED matrix actually works? I mean, the datasheet: http://tronixstuff.com/wp-content/uploads/2010/07/max7219.pdf only describes if it is used with 8 x 7-Segment Displays but not how to turn a dot on / off on a 8x8 matrix. I would be really thankful if anybody could explain to me how i turn a single dot on a 8x8 matrix on.

Thanks

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  • \$\begingroup\$ From Table 5 in the datasheet you linked to, it looks like you can use BLANK (D0=D1=D2=D3=1) with bit D7=1 to power only the DP and no segments, if that is what you are asking. \$\endgroup\$ – Andrew Morton Dec 30 '16 at 22:19
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Set decode mode register 0x9 to 0, which disables the BCD to 7 segment decoding on all digits, then set the appropriate bits for the segment rows in the addresses 0x1 to 0x8 for the first to 8th digit columns.

By default after a reset or on initial power up the intensity is set=0, scan=1 digit and display is blanked (shutdown). So you also have to set:
Set the 0xA intensity value or the display will be minimal brightness.
..set the 0xB scan to the number of digits you want to scan.
..set the 0xC shutdown register to 0x1 to enable scanning oscillator.

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The MAX7219 can drive

7-segment numeric LED displays of up to 8 digits, bargraph displays, or 64 individual LEDs.

7 Segment displays are typically... 8 segments when you count the dot.

8 segments * 8 digits = 64 leds.

The Dot is just another segment that it can drive.

enter image description here

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