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Name: MAX7219
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Author: Gavin Lyons.
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Description:
A library to display data on MAX7219 seven segment module. Raspberry Pi PICO SDK C++ library. Hardware or software SPI, Shutdown mode, test mode and Brightness control supported.
Example files list:
| List No | Example file name | Description |
|---|---|---|
| 1 | src/tests/main.cpp | test sequence |
| 2 | src/bcdmode/main.cpp | Shows use of BCD built-in font |
| 3 | src/cascade_demo/main.cpp | simple Demo showing use of cascaded displays |
There are three examples files(main.cpp) in example folder, To select the one that builds comment it's path in, in the CMakeLists.txt file, section add_executable section. Comment one path in and one ONLY.
To select between hardware and software SPI in examples files see USER OPTION SPI SELECTION section.
For Software SPI Pick any GPIO you want. CommDelay variable (uS Communication delay). This is a communications delay used in Software SPI clocking, default 0.
For Hardware SPI the user must use fixed SPI pins for clock and data, user can choice any GPIO for chip select. The clock and MOSI lines will be linked to the chosen interface i.e spi0, spi1 etc The datasheet says it's a 10 MHZ device, In hardware SPI user can pick SPI bus speed.
| Pin no | PICO SW SPI | PICO HW SPIX | Pin function |
|---|---|---|---|
| 1 | any GPIO output | spiX CLK | CLK = Clock |
| 2 | any GPIO output | any GPIO output | CS = Chip select |
| 3 | any GPIO output | spiX TX | DIN = Data in |
VCC 5V in theory but works at 3.3V in testing, albeit with a dimmer display. Logic seems to work fine at 3.3V , It safe as it is all one way communications From PICO to MAX. User can adjust brightness from 0x00 to 0x0F by default it is 0x08. 0x0F being brightest
Support for Cascaded Displays added is untested as only one display available. Cascaded Displays are displays connected together. Din-> Dout and CS lines tied together.