hi!
Im trying to use a MAX7221 on a 7-segment display.
But i cant get it to work. It flashes very dim for like 0.5s then it go black.
I have tested every single LED independently with just power and a resistor and they all work fine.
I have blue LED and I use 27K resistor as Iset.
5V
3.3V forward
20mA current
If i connect the CC-pin from the 7-Segment to ground via 100Ohm it work. But i suppose its not the right way and probably will damage the chip.
Connect CC to DIG0 and it just flash dim for 0.5s and then go black.
Is it a faulty chip or do i do something wrong here?
Code:
/*
Basic code for using Maxim MAX7219/MAX7221 with Arduino.
Wire the Arduino and the MAX7219/MAX7221 together as follows:
| Arduino | MAX7219/MAX7221 |
| --------- | --------------- |
| MOSI (11) | DIN (1) |
| SCK (13) | CLK (13) |
| I/O (7)* | LOAD/CS (12) |
* - This should match the LOAD_PIN constant defined below.
For the rest of the wiring follow the wiring diagram found in the datasheet.
Datasheet: http://datasheets.maximintegrated.com/en/ds/MAX7219-MAX7221.pdf
Author: Nicholas Dobie <nick@nickdobie.com>
Date: 30 December 2013
License: WTFPL (http://www.wtfpl.net/)
*/
#include <SPI.h>
// What pin on the Arduino connects to the LOAD/CS pin on the MAX7219/MAX7221
#define LOAD_PIN 7
/**
* Transfers data to a MAX7219/MAX7221 register.
*
* @param address The register to load data into
* @param value Value to store in the register
*/
void maxTransfer(uint8_t address, uint8_t value) {
// Ensure LOAD/CS is LOW
digitalWrite(LOAD_PIN, LOW);
// Send the register address
SPI.transfer(address);
// Send the value
SPI.transfer(value);
// Tell chip to load in data
digitalWrite(LOAD_PIN, HIGH);
}
void setup() {
// Set load pin to output
pinMode(LOAD_PIN, OUTPUT);
// Reverse the SPI transfer to send the MSB first
SPI.setBitOrder(MSBFIRST);
// Start SPI
SPI.begin();
// Run test
// All LED segments should light up
maxTransfer(0x0F, 0x01);
delay(1000);
maxTransfer(0x0F, 0x00);
// Enable mode B
maxTransfer(0x09, 0xFF);
// Use lowest intensity
maxTransfer(0x0A, 0x00);
// Only scan one digit
maxTransfer(0x0B, 0x00);
// Turn on chip
maxTransfer(0x0C, 0x01);
}
void loop() {
// Loop through each code
for (uint8_t i = 0; i < 0x10; ++i)
{
maxTransfer(0x01, i);
delay(1000);
}
}
