MAX7219 for LED matrix

Hi,

I'm planning to use MAX7219 drivers in matrix mode to light several indicators and backlight LEDs. I started looking around for documentation on how the addresses/indexes in SimVim translate into segment and digit driver pairs. In other words, if I turn on index 7 from SimVim, which segment pin and digit pin on the MAX7219 does this enable. I built the following map by turning on a single matrix index in SimVim, noting which of the 8x8 LEDs lit up, and mapping that LED to segment/driver pins using a multimeter:

	D7	D6	D5	D4	D3	D2	D1	D0
DP	7	15	23	31	39	47	55	63
A	0	8	16	24	32	40	48	56
B	1	9	17	25	33	41	49	57
C	2	10	18	26	34	42	50	58
D	3	11	19	27	35	43	51	59
E	4	12	20	28	36	44	52	60
F	5	13	21	29	37	45	53	61
G	6	14	22	30	38	46	54	62

Does this map look correct? I had to retest several times, because I was not expecting index 0 to be on the 2nd row of the LED matrix. However, this appears to be how the module works. I'm trying to make sure that I pick indexes which all align with a single digit driver. I don't want to run multiple cathode connections to the same LED group because I picked the wrong index.

Thanks

Mike

Jun 6, 2020 in FAQs, Tips (Archive) by posixPilot

2 Answers

Hi Milton,

Thanks for taking the time to test this out and post pictures. Also, great idea hooking a 7 segment display alongside the matrix; that makes it much easier. I tested the displays again and came out with the same map that I had originally. I notice, when comparing your map to my map, that they are exactly opposite. For your picture 1, I see D0, DP lit, which I index as 63 and you index as 0. Picture 2 I see as D5, DP; my index 23 to your index 40. Picture 3 I see D7,G which is my index 6 to your index 63.

I think maybe we disagree on the naming of the digits. Working from the MAX7219 data sheet, I used my multimeter diode test to light an LED on my 7-segment display. I probed the 7219 pin 22 (SEG DP) with positive, and pin 2 (DIG 0) with negative. This lights the decimal place on the right most digit, with the decimal place at the bottom. It looks identical to your picture MAX7219-1; is it possible you are calling that digit 7?

Thanks

Mike

Jun 10, 2020 by posixPilot

Hi Milton,

I see why we are having difficulty comparing our setup. My module is exactly the opposite of yours, given the same orientation (see picture below). Also, I have been referring to SimVim index numbers, where as you have been referring to locations on the LED matrix. In the image below, the blue numbers represent SimVim index numbers.

https://ibb.co/DWRqbYF

The yellow index 41 is the LED that lights up when I configure SimVim like this and press the MKR button in XPlane:

[Output] L30.41 Audio_MKR_On

Below is the result when I hook up the matrix and 7-segment to SimVim and press the MKR button. SimVim index 41 lights on the matrix, and D2, SEGB lights on the 7-segment display. At least for my purposes, I'm trying to figure out why the indexes for segment DP are out of order. If I wire my project with the way SimVim maps this today, I'm afraid it might change in the future.

https://ibb.co/2kbKJQR

Thanks

Mike

Jun 10, 2020 by posixPilot

MAX7219 for LED matrix

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	D7	D6	D5	D4	D3	D2	D1	D0
DP	7	15	23	31	39	47	55	63
A	0	8	16	24	32	40	48	56
B	1	9	17	25	33	41	49	57
C	2	10	18	26	34	42	50	58
D	3	11	19	27	35	43	51	59
E	4	12	20	28	36	44	52	60
F	5	13	21	29	37	45	53	61
G	6	14	22	30	38	46	54	62

	D7	D6	D5	D4	D3	D2	D1	D0
DP	7	15	23	31	39	47	55	63
A	0	8	16	24	32	40	48	56
B	1	9	17	25	33	41	49	57
C	2	10	18	26	34	42	50	58
D	3	11	19	27	35	43	51	59
E	4	12	20	28	36	44	52	60
F	5	13	21	29	37	45	53	61
G	6	14	22	30	38	46	54	62

	D7	D6	D5	D4	D3	D2	D1	D0
DP	7	15	23	31	39	47	55	63
A	0	8	16	24	32	40	48	56
B	1	9	17	25	33	41	49	57
C	2	10	18	26	34	42	50	58
D	3	11	19	27	35	43	51	59
E	4	12	20	28	36	44	52	60
F	5	13	21	29	37	45	53	61
G	6	14	22	30	38	46	54	62