158 lines
8.8 KiB
Arduino
158 lines
8.8 KiB
Arduino
 
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/*==============================================================================
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MAX7219CNG.ino - driver for the MAX7219 (or compatible, e.g. MAX7221/CNG clone)
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LED display driver IC.
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Hardware: unlike the MM5450 driver in this project, the MAX7219 has its OWN
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internal digit scan/multiplexing (up to 8 digits) and its own PWM intensity
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control (REG_INTENSITY, 16 steps), so this driver does NOT use the periodic
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hardware-timer ISR / startTimer() at all - there is no writeDisplay() ISR
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here, only a blocking writeDisplaySingle() that pushes one full frame (all
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digits) whenever the displayed content changes. The chip keeps refreshing
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the LEDs by itself between calls.
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Wiring/protocol: standard MAX72xx 3-wire serial bus (DIN/CLK/LOAD-CS), bit-
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banged with shiftOut() (MSBFIRST) rather than hardware SPI. Each 16-bit
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transfer is {8-bit register/digit address, 8-bit data}, latched into the
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chip's internal register on the LOAD/CS_ rising edge. This driver runs the
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chip in "No-Decode" mode (REG_DECODE=0) so it can drive arbitrary custom
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7-segment patterns (including the extra glyphs A,P,C,deg,%,I,F) instead of
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the chip's built-in BCD/font decoder, which only knows digits 0-9 and a few
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symbols.
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Used by (see clocks.h): CLOCK_10 - "8266 LED Clock with MAX7219 chip"
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(clocks.h defines MAX7219CNG only inside the #ifdef CLOCK_10 block).
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==============================================================================*/
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#ifdef MAX7219CNG
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char tubeDriver[] = "MAX7219CNG";
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int maxDigits = 6;
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byte tubes[] = {0,1,2,3,4,5}; //change it, if needed for the correct tube sequence
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// tubes[i] maps logical digit position i (0..maxDigits-1, left to right as wired to the
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// MAX7219's DIG0..DIG7 addresses) to the index into the shared digit[]/digitDP[] buffers -
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// lets the PCB wire digits in any physical order without changing the core clock logic.
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byte brightConvert[] = {0,1,2,3,4,6,8,10,12,14,15}; //convert brightness from 0..10 to 0..15
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// Non-linear lookup table: the firmware-wide brightness scale is 0..10 (MAXBRIGHTNESS=10
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// for CLOCK_10), but REG_INTENSITY wants 0..15 - this table also biases the mapping
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// (skipping value 5/7/etc.) so perceived brightness steps feel more even than a plain x1.5 scale.
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//MAX7219CNG control pins
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#define PIN_LOAD 15 // D8 LOAD/CS_
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#define PIN_CLK 14 // D5 Clock
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#define PIN_DIN 13 // D7 DataIN
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//MAX7219 Registers (see MAX7219/MAX7221 datasheet "Table 2. Register Address Map")
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#define REG_SHUTDOWN 0x0C // 0 = shutdown (blank, low power), 1 = normal operation
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#define REG_SCANLIMIT 0x0B // how many digits (0..7, i.e. count-1) the chip actively multiplexes
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#define REG_DECODE 0x09 // per-digit BCD-decode enable bitmask; 0 = No-Decode (raw segment bits, used here)
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#define REG_INTENSITY 0x0A // global PWM duty cycle for all digits, 0x00 (dimmest) .. 0x0F (brightest)
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#define REG_TEST 0x0F // 1 = display-test mode (forces all segments on at full brightness), 0 = normal
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//------------------abcdefgDP---------------- definition of different characters
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byte charDefinition[] = {
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B11111100, //0: abcdef
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B01100000, //1: bc
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B11011010, //2: abdeg
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B11110010, //3: abcdg
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B01100110, //4: bcfg
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B10110110, //5: acdfg
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B10111110, //6: acdefg
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B11100000, //7: abc
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B11111110, //8: abcdefg
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B11110110, //9: abcdfg
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B00000000, // : BLANK (10)
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B00000010, //-: minus (11)
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B00000001, // decimal point (12)
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B11101110, // A abcefg (13)
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B11001110, // P abefg (14)
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B10011100, // C adef (15)
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B11000110, //grad (upper circle) abfg (16)
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B10110100, //% acdf (17)
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B00111010, //lower circle cdeg (18)
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B01100000, //I bc (19)
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B10001110 //F aefg (20)
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};
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//Fill this table with the output-bit numbers of the MAX7219 chip! Only No-Decode mode is used, for flexible hardware
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// segmentEnablePins[j] = which bit position (0..7) within the MAX7219's per-digit data
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// byte drives logical segment j (a,b,c,d,e,f,g,DP) - lets the segment-to-pin wiring on the
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// PCB differ from the charDefinition[] bit order without touching the font table itself.
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byte segmentEnablePins[] = {6,5,4,3,2,1,0,7}; //segment enable bits of MAX7219 (a,b,c,d,e,f,g,DP) (You MUST always define 8 bits!!!)
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#define MAXCHARS sizeof(charDefinition) // (currently unused in this file - kept for reference/consistency with other drivers)
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#define MAXSEGMENTS 8 // (currently unused in this file)
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// Sends one 16-bit MAX7219 command: {address (register or digit 1..8), data byte}.
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// LOAD/CS_ must be held LOW for the whole 16-bit transfer and pulsed HIGH afterward to
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// latch it - the chip ignores clock edges while LOAD is high, so partial/torn writes
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// are not possible even though this is a blocking (non-ISR) call.
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void ICACHE_RAM_ATTR sendBits(byte address,byte val){
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digitalWrite(PIN_LOAD, LOW);
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shiftOut(PIN_DIN, PIN_CLK, MSBFIRST, address);
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shiftOut(PIN_DIN, PIN_CLK, MSBFIRST, val);
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digitalWrite(PIN_LOAD, HIGH);
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delay(3); // conservative settle/latch delay; MAX7219 datasheet only requires ~tCSW ~ 50ns,
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// so this is far more generous than strictly needed (see optimization note in report)
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//DPRINT(address,HEX); DPRINT(","); DPRINTLN(val,HEX);
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}
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void setup_pins() {
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#if defined(ESP8266)
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#else
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#error "Only 8266 Board is supported!"
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#endif
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DPRINTLN("MAX7219 Clock - setup pins...");
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pinMode(PIN_LOAD,OUTPUT); regPin(PIN_LOAD,"PIN_LOAD");
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pinMode(PIN_DIN, OUTPUT); regPin(PIN_DIN,"PIN_DIN");
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pinMode(PIN_CLK, OUTPUT); regPin(PIN_CLK,"PIN_CLK");
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digitsOnly = false; // this driver's charDefinition[] also supports letters (A,P,C,deg,%,I,F) besides 0-9
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// Note: no startTimer() call here - this driver relies on the MAX7219's own internal
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// digit multiplexing, so no software multiplex/PWM ISR is needed for this chip.
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sendBits(REG_SHUTDOWN,1); //Set to Normal (not Shutdown) mode
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sendBits(REG_TEST,0); //Set to Normal, (Non-Test) mode
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sendBits(REG_SCANLIMIT,maxDigits-1); //Set scanlimit (chip multiplexes digits 0..maxDigits-1 only)
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sendBits(REG_DECODE,0 ); //Set Non-Decode Mode - segment data is sent as raw bit patterns, not BCD
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sendBits(REG_INTENSITY,0x0F); //Set maximum brightness (actual runtime brightness is set per-frame in writeDisplaySingle())
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}
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// Blocking, one-shot push of the ENTIRE current frame (all digits + brightness) to the
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// MAX7219. Called directly from the main sketch (not from an ISR - despite the
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// ICACHE_RAM_ATTR tag, likely inherited from other drivers' ISR-based writeDisplay()
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// pattern; harmless here, just places the function in IRAM instead of flash).
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// Because the MAX7219 keeps displaying the last-latched frame by itself (on-chip
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// multiplexing), this only needs to run when digit[]/digitDP[]/brightness actually change -
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// there is no periodic refresh ISR for this driver (see setup_pins() note).
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void ICACHE_RAM_ATTR writeDisplaySingle() {
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static byte oldBright = 0;
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static byte newBright = 0;
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int bitBuffer;
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//https://sub.nanona.fi/esp8266/timing-and-ticks.html
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//One tick is 1us / 80 = 0.0125us = 12.5ns on 80MHz
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//One tick is 1us / 80 = 0.0125us = 6.25ns on 160MHz
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// 1 NOP is 1 tick
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// (NOP-timing reference is a leftover from the bit-banged drivers - this file uses
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// shiftOut()/delay() instead and doesn't rely on cycle-counted NOPs)
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newBright = brightConvert[displayON ? prm.dayBright : prm.nightBright]; //convert 0..10 brightness levels to 0..15
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if (!radarON) newBright = 0; // no presence detected -> force display off (still fully addressed/latched, just at 0 intensity)
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if (newBright != oldBright) { // only touch the INTENSITY register when the value actually changed, to save a 16-bit transfer + 3ms delay
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sendBits(REG_INTENSITY, newBright); //Set Brightness
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oldBright = newBright;
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}
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for (int i=0;i<maxDigits;i++) {
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bitBuffer = 0;
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for (int j=0;j<=7;j++) //from a to g
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if ((charDefinition[digit[tubes[i]]] & 1<<(7-j)) != 0) {
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bitBuffer |= 1<<segmentEnablePins[j];
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}
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if (digitDP[tubes[i]]) bitBuffer |= 1<<segmentEnablePins[7]; //Decimal Point
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sendBits(i+1, bitBuffer); // MAX7219 digit registers are addressed 1..8 (DIG0..DIG7), hence i+1
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} //end for i
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}
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void clearTubes() {} // no-op: since there's no refresh ISR, "clearing" would require an explicit
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// blank frame write, which this driver leaves to the next writeDisplaySingle()
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// call (or REG_SHUTDOWN could be used, but isn't here)
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#endif
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