LED Matrix Dsply


LED Matrix Programming8x8-LED-Matrix LedControl.cpp Custom-Seven-Segment-LED
MAX7219-MAX7221 DataSheet Led7Seg Sketch LedControl LedCascade
MAX72xx MAX7219 LedCtrlLib LedCtrlSftw
LedDemos LedMtrx LedCtrlHdw 8x8 LED generator
Real 8x8 LED Gen LedControl Info Max7219 Clock Max7219 Clock
MD_MAX72xx.cpp MD_MAX72xx.ESP32 LedMtx & ESP32 Matrix Characters
ESP32 Matrix

In-Page links
NTP LED Matrix RTC ESP01

The MAX72xx uses an SPI interface, and it's Vcc is 5V. On SPI interface, the MAX72xx only uses MOSI as it's data pin.

I want an NTP controlled clock for numerous projects.   Yes, I do need another clock in our Den and bedroom (with a projector), but I also need a thermostat for the mini-split AC in the shop and our irrigation controller.   So I got busy.  

MAX7219 Vcc: 3.3 - 5V

  1. First was to be able to get the NTP packets from our NTP server and extract the time information in a format compatable with an RTC card.
  2. be able to pull the time/date etc. from the RTC
  3. display it on a display large enough for Betty and I to see (we're both seniors).  

NTP Packets

I originally started out using an Arduino Nano and an ESP01 adapter with an esp8266, but found I had consumed too much ram.   So I switched to an ESP32 and was pleased with result (so far).

RTC

The RTC (Real Time Clock) is a DS3231 which appears to be well supported.  

LED Matrix

A most of the LCD displays were either too small or too expensive, when I came upon the 32x8 LED Matrix displays.      

Bottom of a 32x8 LED MATRIX (MAX7219 control chip).   You can see the signal names (albeit upside down) on the main IO connector.
There are at least 3 types:
Red: 1088AS ?
Blu: 1088AB 46
Grn: 1088AYG  

SigNanoESP32NodeMCU
Vin5V5V
GndGndGnd
DinD11 (MOSI)23 (vspi MOSI)
ClkD13 (SCK)18 (vspi SCK)
Cs*D7D7

(V+ = 5V ±10%, R SET = 9.53kΩ ±1%, T A = T MIN to T MAX , unless otherwise noted.) 1 µA
PARAMETER SYMBOLCONDITIONS MIN TYP MAX UNITS
LOGIC INPUTS
Input Current DIN, CLK, LOAD, CS I IH , I IL V IN = 0V or V+ -1 1 uA
Logic High Input Voltage V IH 3.5 V
Logic Low Input Voltage V IL 0.8 V
Output High Voltage V OH DOUT, I SOURCE = -1mA V+ - 1 V
Output Low Voltage V OL DOUT, I SINK = 1.6mA 0.4 V
Hysteresis Voltage ΔV I DIN, CLK, LOAD, CS 1 V
TIMING CHARACTERISTICS
CLK Clock Period t CP 100 ns
CLK Pulse Width High t CH 50 ns
CLK Pulse Width Low t CL 50 ns CS Fall to SCLK Rise Setup Time (MAX7221 only) t CSS 25 ns CLK Rise to CS or LOAD Rise Hold Time t CSH 0 ns DIN Setup Time t DS 25 ns DIN Hold Time t DH 0 ns Output Data Propagation Delay t DO Load-Rising Edge to Next Clock Rising Edge (MAX7219 only) t LDCK 50 ns Minimum CS or LOAD Pulse High t CSW 50 ns Data-to-Segment Delay t DSPD www.maximintegrated.com C LOAD = 50pF 25 2.25 ns ms