/** * Copyright (c) 2022 Raspberry Pi (Trading) Ltd. * * SPDX-License-Identifier: BSD-3-Clause */ #include <stdio.h> #include <string.h> #include "pico/stdlib.h" #include "pico/binary_info.h" #include "hardware/spi.h" /* Example code to talk to a Max7219 driving an 32x8 pixel LED display via SPI NOTE: The device is driven at 5v, but SPI communications are at 3v3 Connections on Raspberry Pi Pico board and a generic Max7219 board, other boards may vary. * GPIO 17 (pin 22) Chip select -> CS on Max7219 board * GPIO 18 (pin 24) SCK/spi0_sclk -> CLK on Max7219 board * GPIO 19 (pin 25) MOSI/spi0_tx -> DIN on Max7219 board * 5v (pin 40) -> VCC on Max7219 board * GND (pin 38) -> GND on Max7219 board Note: SPI devices can have a number of different naming schemes for pins. See the Wikipedia page at https://en.wikipedia.org/wiki/Serial_Peripheral_Interface for variations. */ // This defines how many Max7219 modules we have cascaded together, in this case, we have 4 x 8x8 matrices giving a total of 32x8 #define NUM_MODULES 4 const uint8_t CMD_NOOP = 0; const uint8_t CMD_DIGIT0 = 1; // Goes up to 8, for each line const uint8_t CMD_DECODEMODE = 9; const uint8_t CMD_BRIGHTNESS = 10; const uint8_t CMD_SCANLIMIT = 11; const uint8_t CMD_SHUTDOWN = 12; const uint8_t CMD_DISPLAYTEST = 15; #ifdef PICO_DEFAULT_SPI_CSN_PIN static inline void cs_select() { asm volatile("nop \n nop \n nop"); gpio_put(PICO_DEFAULT_SPI_CSN_PIN, 0); // Active low asm volatile("nop \n nop \n nop"); } static inline void cs_deselect() { asm volatile("nop \n nop \n nop"); gpio_put(PICO_DEFAULT_SPI_CSN_PIN, 1); asm volatile("nop \n nop \n nop"); } #endif #if defined(spi_default) && defined(PICO_DEFAULT_SPI_CSN_PIN) static void write_register(uint8_t reg, uint8_t data) { uint8_t buf[2]; buf[0] = reg; buf[1] = data; cs_select(); spi_write_blocking(spi_default, buf, 2); cs_deselect(); sleep_ms(1); } static void write_register_all(uint8_t reg, uint8_t data) { uint8_t buf[2]; buf[0] = reg; buf[1] = data; cs_select(); for (int i = 0; i< NUM_MODULES;i++) { spi_write_blocking(spi_default, buf, 2); } cs_deselect(); } #endif int main() { stdio_init_all(); #if !defined(spi_default) || !defined(PICO_DEFAULT_SPI_SCK_PIN) || !defined(PICO_DEFAULT_SPI_TX_PIN) || !defined(PICO_DEFAULT_SPI_CSN_PIN) #warning spi/max7219_32x8_spi example requires a board with SPI pins puts("Default SPI pins were not defined"); #else printf("Hello, max7219! Drawing things on a LED matrix since 2022...\n"); // This example will use SPI0 at 10MHz. spi_init(spi_default, 10 * 1000 * 1000); gpio_set_function(PICO_DEFAULT_SPI_SCK_PIN, GPIO_FUNC_SPI); gpio_set_function(PICO_DEFAULT_SPI_TX_PIN, GPIO_FUNC_SPI); // Make the SPI pins available to picotool bi_decl(bi_2pins_with_func(PICO_DEFAULT_SPI_TX_PIN, PICO_DEFAULT_SPI_SCK_PIN, GPIO_FUNC_SPI)); // Chip select is active-low, so we'll initialise it to a driven-high state gpio_init(PICO_DEFAULT_SPI_CSN_PIN); gpio_set_dir(PICO_DEFAULT_SPI_CSN_PIN, GPIO_OUT); gpio_put(PICO_DEFAULT_SPI_CSN_PIN, 1); // Make the CS pin available to picotool bi_decl(bi_1pin_with_name(PICO_DEFAULT_SPI_CSN_PIN, "SPI CS")); // Send init sequence to device write_register_all(CMD_SHUTDOWN, 0); write_register_all(CMD_DISPLAYTEST, 0); write_register_all(CMD_SCANLIMIT, 7); // Use all lines write_register_all(CMD_DECODEMODE, 0); // No BCD decode, just use bit pattern. write_register_all(CMD_SHUTDOWN, 1); write_register_all(CMD_BRIGHTNESS, 8); for (int i=0; i<256; i++) { for (int j=0; j<8; j++) { write_register_all(CMD_DIGIT0+j, i); } sleep_ms(20); } int bright = 1; while (true) { for (int i=0; i<8; i++) { if (bright & 1) { write_register_all(CMD_DIGIT0 + i, 170 >> (i%2)); } else { write_register_all(CMD_DIGIT0 + i, (170 >> 1) << (i%2)); } write_register_all(CMD_BRIGHTNESS, bright % 16); } sleep_ms(250); bright++; } #endif }

This firmware image was imported from the pico-examples repository. 


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