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gmarsh wrote:If you're going "big" (500+ LEDs) then an implementation like this might be what you're after. I'll post design/schematics/pictures/etc if anyone's interested.Greetings (No Name Supplied),
bigglez wrote:The serial 3-wire interface requires a clock and data to send the data to the MAX ic. When all the serial data is read in the third line is used to load the new data (MAX7219). The CS/ line is used to select (activate) the device (MAX7221), which is structured differently to the MAX7219 to make it compatible with published bus structures (microwire, SPI, QSPI).Are there any practical differences between using the two interfaces? It seems to me that for daisy-chained devices, it might be easier to use the 7221 and tie all CS/ lines to GND, to avoid having to toggle LOAD on a 7291. Plus the 7221 is slew rate limited, which might be useful in some cases.
My personal choice would be the MAX7219 with DIN,CLK, LOAD as I've used this format before, and don't plan to interface with the other standards that require a CS/ line.
Lucien wrote:Are there any practical differences between using the two interfaces? It seems to me that for daisy-chained devices, it might be easier to use the 7221 and tie all CS/ lines to GND, to avoid having to toggle LOAD on a 7291. Plus the 7221 is slew rate limited, which might be useful in some cases.Greetings Lucien,
bigglez wrote:No doubt others will jump in here with application hints!My suggestion: Arrange "matrix" (using "no decode" option) in a single row of LEDs across a piano keyboard, one LED per key, then write some VB code to switch each LED on or off (max 10 simultaneously) in order to provide a rudimentary "guide lights" feature such as found on expensive Yamaha keyboards.
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