Files
nixie-clock/firmware/uniclock/ESP32_UniClock2/MAX6921_ESP32.ino
T
mangavalkandClaude Opus 5.5 b347f1c63f Import ESP_UniClock (upstream 1189810)
Vendored from https://github.com/gpeter62/ESP_UniClock: the sketch
source, the web UI and the libraries the ESP8266 build needs, unpacked
from the bundled zips. Adds a PlatformIO project for the ESP-12. The
source is unchanged; local changes follow as separate commits.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-25 20:48:04 +01:00

310 lines
18 KiB
Arduino

#ifdef MAX6921_ESP32
//===========================================================================================
// Driver for the MAXIM MAX6921 20-output VFD/vacuum-tube driver chip -- ESP32 variant.
// This is the ESP32 port of MAX6921.ino; the protocol/chip behaviour is identical, only the
// platform-specific timer/interrupt plumbing differs (ESP32 hardware timer + spinlock instead
// of ESP8266 timer1; IRAM_ATTR/DRAM_ATTR instead of ICACHE_RAM_ATTR). See MAX6921.ino's header
// for the full protocol writeup (SPI-like DATA/CLK/LE shift register + BLANK).
//
// Hardware / protocol summary:
// 20-bit serial shift register + latch, MSB (OUT19) first on DATA, one CLK pulse per bit,
// LE (Latch Enable) pulses HIGH->LOW after the 20 bits to atomically transfer the shift
// register into the output latch, BL (BLANK, active HIGH) forces all outputs off. Which
// output pin drives a segment vs. a tube's digit-select grid is purely PCB wiring, described
// by segmentEnablePins[8]/digitEnablePins[] in clocks.h.
//
// Used by (see clocks.h, search for "#define MAX6921_ESP32"):
// CLOCK_26 - ESP32 D1 mini, UNFI 6x IV-11 VFD tubes clock, SHT21 sensor
// CLOCK_30 - ESP32, UNFI PCB clock, 6x IV-11 VFD tubes
// CLOCK_32 - ESP32, UNFI 6x IV-11 VFD tubes clock, DHT22 sensor
// CLOCK_40 - V1 ESP32, UNFI 6x IV-11 VFD tubes clock
// CLOCK_41 - V2 ESP32, UNFI 6x IV-11 VFD tubes clock (jumper wire)
// CLOCK_42 - V3 ESP32, UNFI 6x IV-11 VFD tubes clock
// CLOCK_47 - V3 ESP32, UNFI 10-LT-50G VFD tubes clock
// (all ESP32 boards -- the ESP8266 counterpart configs use MAX6921.ino instead, see that
// file's header for their CLOCK_NN list.)
//===========================================================================================
//VFD driver for ESP32
char tubeDriver[] = "MAX6921_ESP32";
#if defined(ESP32)
#else
#error "Only ESP32 board is supported by this driver!"
#endif
// POSSIBLE BUG (minor / dead code): declared but never assigned or referenced anywhere else in
// this file (or the project, unlike the same-named `maxDig` pattern used by e.g.
// multiplex74141_ESP32.ino / Numitron_4511N.ino, where it actually caches maxDigits and is used
// in the ISR). Here it is vestigial and can be removed; `maxDigits` is used directly instead.
int DRAM_ATTR maxDig; //memory variable version of maxDigits
//------------------abcdefgDP---------------- definition of different characters
// Each byte below is one glyph's segment pattern, bit7..bit0 = a,b,c,d,e,f,g,DP (a=MSB).
// See generateBitTable(): these abstract a..g/DP bits get remapped through segmentEnablePins[]
// (the PCB-specific wiring) into the actual MAX6921 OUTx bits, producing charTable[].
// Indices 0-9 are digits; 10-20 are special glyphs referenced via the digit[] buffer.
byte DRAM_ATTR charDefinition[] = {
B11111100, //0: abcdef
B01100000, //1: bc
B11011010, //2: abdeg
B11110010, //3: abcdg
B01100110, //4: bcfg
B10110110, //5: acdfg
B10111110, //6: acdefg
B11100000, //7: abc
B11111110, //8: abcdefg
B11110110, //9: abcdfg
B00000000, // : BLANK (10)
B00000010, //-: minus (11)
B00000001, // decimal point (12)
B11101110, // A abcefg (13)
B11001110, // P abefg (14)
B10011100, // C adef (15)
B11000110, //grad (upper circle) abfg (16)
B10110100, //% acdf (17)
B00111010, //lower circle cdeg (18)
B01100000, //I bc (19)
B10001110 //F aefg (20)
};
uint32_t DRAM_ATTR animationMaskBits[5]; //precomputed AND-masks for the "wipe" transition animation (animMask[]), see generateBitTable(). DRAM_ATTR pins these in internal RAM so the IRAM-resident ISR can access them without touching flash-cached memory.
// NOTE: MAXCHARS/MAXSEGMENTS/maxDigits rely on sizeof() over `byte` arrays (1 byte/element),
// so sizeof() == element count here. segmentEnablePins[] must always have exactly 8 entries
// (a,b,c,d,e,f,g,DP) per the clocks.h convention; digitEnablePins[] length = number of tubes.
#define MAXCHARS sizeof(charDefinition)
#define MAXSEGMENTS sizeof(segmentEnablePins)
int maxDigits = sizeof(digitEnablePins);
uint32_t DRAM_ATTR charTable[MAXCHARS]; //generated pin table from segmentDefinitions
uint32_t DRAM_ATTR segmentEnableBits[MAXSEGMENTS]; //bitmaps, generated from EnablePins tables
// FIXED (was fixed-size [10] regardless of the actual maxDigits): sized to BUFSIZE (12, see the
// digit[]/newDigit[]/animMask[] buffers in ESP32_UniClock2.ino), the same ceiling the rest of the
// codebase uses for tube-position buffers, so this can no longer silently overflow in
// generateBitTable() for any config the system otherwise supports.
uint32_t DRAM_ATTR digitEnableBits[12];
// Multiplex/brightness timing. Despite the variable names, these are NOT milliseconds -- they
// are raw ESP32 hardware-timer tick counts (see startTimer() in ESP32_UniClock2.ino: PRESCALER=15
// divides the 80MHz APB clock down to roughly a few MHz, so each tick is on the order of 0.2us).
// So PWMrefresh=5500 ticks is roughly ~1ms per ON/OFF half-cycle, PWM_min/PWM_max similarly small.
// Greater PWMrefresh => slower multiplex/refresh frequency (more visible flicker risk).
// All DRAM_ATTR here for the same reason as above: read from inside an IRAM-resident ISR.
int DRAM_ATTR PWMrefresh=5500; //Multiplex time period, in timer ticks (not milliseconds, despite the variable name -- see note above). Greater value => slower multiplex frequency
int DRAM_ATTR PWM_min = 500;
int DRAM_ATTR PWM_max = 5000;
//int DRAM_ATTR PWMtiming[11] = {0,500,800,1200,2000,2500,3000,3500,4000,4500,5000};
//-----------------------------------------------------------------------------------------
//https://sub.nanona.fi/esp8266/timing-and-ticks.html
//One tick is 1us / 80 = 0.0125us = 12.5ns on 80MHz
//One tick is 1us / 80 = 0.0125us = 6.25ns on 160MHz
// 1 NOP is 1 tick
// Dead/no-op helper: `d` is ignored, so this always executes exactly three NOPs regardless of
// the requested delay. Not called anywhere in this file (see the commented-out delayMS(1) call
// sites in writeDisplay() below) -- relies instead on digitalWrite()'s own call overhead to
// satisfy MAX6921 minimum pulse-width timing.
void inline delayMS(int d) {
asm volatile ("nop");
asm volatile ("nop");
asm volatile ("nop");
}
void setup_pins() {
DPRINTLN("VFD Clock - setup MAX6921 pins");
pinMode(PIN_LE, OUTPUT); regPin(PIN_LE,"PIN_LE");
pinMode(PIN_BL, OUTPUT); regPin(PIN_BL,"PIN_BL");
digitalWrite(PIN_BL,LOW); //brightness
pinMode(PIN_DATA,OUTPUT); regPin(PIN_DATA,"PIN_DATA");
pinMode(PIN_CLK, OUTPUT); regPin(PIN_CLK,"PIN_CLK");
// Build a human-readable dump of the pin mapping for the web UI's diagnostics page (not
// used by the driver logic itself).
driverSetupStr = "MAX6921 segmentEnablePins:";
for (int j=0;j<sizeof(segmentEnablePins);j++) {
driverSetupStr += String(segmentEnablePins[j]) + ",";
}
driverSetupStr += "<br>MAX6921 digitEnablePins:";
for (int j=0;j<sizeof(digitEnablePins);j++) {
driverSetupStr += String(digitEnablePins[j]) + ",";
}
driverSetupStr += String("<br>");
generateBitTable(); //precompute charTable/digitEnableBits/animationMaskBits once, so the ISR (writeDisplay) never has to do this math
digitsOnly = false; //this driver can show letters/symbols too (A,P,C,deg,%,I,F...), not just 0-9
startTimer(); //arms the ESP32 hardware timer and attaches writeDisplay() as its ISR -- multiplexing runs entirely in the background from here on
}
// Hardware-timer ISR (ESP32). Unlike the ESP8266 timer1 (one-shot, must be manually
// rearmed every call), timerAlarmWrite(..., true) below enables auto-reload, so the timer
// keeps firing periodically on its own; the repeated timerAlarmWrite()/timerAlarmEnable()
// calls at the end of every invocation just update the *next* period's length (for the
// following ON or OFF phase) rather than being strictly required to keep it running.
// Implements brightness via a simple two-phase (ON/OFF) time-slicing scheme rather than true
// PWM: each call toggles `state` between an "ON phase" (tube lit, duration proportional to
// brightness) and an "OFF phase" (tube dark, remaining time of the PWMrefresh period).
void IRAM_ATTR writeDisplay(){ //void IRAM_ATTR writeDisplay(){
static DRAM_ATTR int timer = PWMrefresh;
static DRAM_ATTR uint32_t val;
static DRAM_ATTR byte pos = 0;
static DRAM_ATTR boolean state=true;
static DRAM_ATTR int brightness;
static DRAM_ATTR int PWMtimeBrightness=PWM_min;
if (EEPROMsaving) { //stop refresh, while EEPROM write is in progress! (EEPROM writes are blocking/slow, and touching them concurrently with flash-adjacent SPI activity risks corruption)
//digitalWrite(PIN_BL,HIGH); //OFF
// NOTE: unlike MAX6921.ino (ESP8266), BL is NOT forced HIGH here, so the display is left
// showing whatever frame was last latched (frozen, not blanked) for the duration of the
// EEPROM write. Also, no timerAlarmWrite()/timerAlarmEnable() call is needed here (unlike
// the ESP8266 timer1_write() call in the sibling file) because this hardware timer's
// auto-reload keeps it firing on its own even while this ISR body returns early.
return;
}
// portENTER_CRITICAL_ISR + noInterrupts()/interrupts() together ensure this whole bit-bang
// sequence (and the shared `val`/`pos`/`state` statics) cannot be interrupted or preempted
// by the other CPU core or a higher-priority ISR mid-frame, which would otherwise risk
// shifting out a half-updated/torn frame to the MAX6921.
portENTER_CRITICAL_ISR(&timerMux);
noInterrupts();
intCounter++;
brightness = displayON ? prm.dayBright : prm.nightBright; //day/night dimming level, selected by the core's displayON flag
if (brightness>MAXBRIGHTNESS) brightness = MAXBRIGHTNESS; //only for safety
if ((!autoBrightness) && (brightness==MAXBRIGHTNESS)) state = true; //at max fixed brightness, always stay in the "ON" phase (skip the OFF/dimming phase entirely)
if (state) { //ON state: advance to the next tube position and compute what to shift out
pos++; if (pos>maxDigits-1) { //go to the tube#0
pos = 0;
// Brightness (PWM ON time) is only recalculated once per full multiplex sweep (at tube#0),
// not per-tube, so all tubes share the same duty cycle within one refresh cycle.
if (autoBrightness && displayON) { //change brightness only on the tube#0
PWMtimeBrightness = max(PWM_min,PWM_max*lx/MAXIMUM_LUX); //ambient-light-driven brightness (auto-dimming), scaled by measured lux vs MAXIMUM_LUX
}
else
PWMtimeBrightness = max(PWM_min,PWM_max*brightness/MAXBRIGHTNESS); //manual brightness setting, scaled 0..MAXBRIGHTNESS into PWM_min..PWM_max ticks
}
// MAX6921 has no separate "digit select" vs "segment" concept -- both are just output
// bits. Combine the bit for this tube's grid/anode-enable output with the bits for the
// segments that should light up for the current character into one 20-bit frame.
val = (digitEnableBits[pos] | charTable[digit[pos]]); //the full bitmap to send to MAX chip
if (digitDP[pos]) val = val | charTable[12]; //Decimal Point (charTable[12] = the DP-only glyph, OR'd in independently of the digit glyph)
timer = PWMtimeBrightness;
//if (pos==2) timer = 3*timer; //Weak IV11 tube#2 brightness compensation -- see the CLOCK_4-guarded equivalent in MAX6921.ino; no ESP32 clocks.h config currently needs this hack, left disabled here
timerON = timer; //exposed for debug/diagnostics only (see ESP32_UniClock2.ino)
timerOFF = PWMrefresh-PWMtimeBrightness;
}
else { //OFF state: nothing to shift out this call, just wait out the rest of the duty cycle
timer = PWMrefresh-PWMtimeBrightness;
}
if (timer<500) timer = 500; //safety only... avoid an excessively short/zero timer reload that could starve the CPU with ISR re-entry
if ( (brightness == 0) || (!state) || (!radarON)) { //OFF state, blank digit (radarON gates the whole display off when a presence/radar sensor says nobody is around)
digitalWrite(PIN_BL,HIGH); //OFF
}
else { //ON state
if (animMask[pos]>0) val &= animationMaskBits[animMask[pos]-1]; //animationMode 6, mask characters from up to down and back -- animMask[] holds a 1-based progressive-reveal stage per tube; the precomputed masks blank segments in a..g order to fake a vertical wipe
// Bit-bang 20 bits out MSB-first (OUT19 first). No explicit delay is inserted between
// digitalWrite() calls: the GPIO register write + digitalWrite() call overhead already
// exceeds the MAX6921's minimum DIN setup/CLK pulse-width requirement, so the
// commented-out nop/delayMS() calls below are intentionally left disabled.
for (int i=0; i<20; i++) {
if (val & uint32_t(1 << (19 - i)))
{digitalWrite(PIN_DATA, HIGH); //asm volatile ("nop");
}
else
{digitalWrite(PIN_DATA, LOW); //asm volatile ("nop");
}
digitalWrite(PIN_CLK,HIGH); //asm volatile ("nop"); //delayMS(1); //rising edge shifts the current DATA bit into the MAX6921 internal shift register
digitalWrite(PIN_CLK,LOW); //asm volatile ("nop"); //delayMS(1);
} //end for
// Latch pulse: transfers the 20-bit shift register into the MAX6921's output latch in one
// shot, so the outputs (and thus the tube) change atomically rather than rippling bit by
// bit while still shifting (which would show visible garbage/flicker on the tube).
digitalWrite(PIN_LE,HIGH ); asm volatile ("nop");
digitalWrite(PIN_LE,LOW);
digitalWrite(PIN_BL,LOW ); //ON -- unblank now that the new frame is safely latched
} //end else
portEXIT_CRITICAL_ISR(&timerMux);
state = !state;
//ESP32timer = timerBegin(0, PRESCALER, true); //set prescaler, true = edge generated signal
//timerAttachInterrupt(ESP32timer, &writeDisplay, true);
timerAlarmWrite(ESP32timer, timer, true); //schedule the next phase's (ON or OFF) duration; `true` keeps auto-reload enabled
timerAlarmEnable(ESP32timer);
interrupts();
}
// One-time setup helper (called from setup_pins()): translates the PCB-specific pin-index
// tables from clocks.h (segmentEnablePins[], digitEnablePins[]) and the abstract a..g/DP
// glyph patterns (charDefinition[]) into ready-to-OR 32-bit MAX6921 output bitmaps. Doing
// this heavy lifting once at boot keeps the writeDisplay() ISR itself lightweight (just a
// couple of array lookups + OR + bit-shift loop).
void generateBitTable() {
uint32_t out;
DPRINTLN("--- Generating segment pins bitmap ---");
for (int i=0;i<MAXSEGMENTS;i++) {
segmentEnableBits[i] = uint32_t(1<<segmentEnablePins[i]); //one-hot bit for each of the 8 segment output pins (a..g,DP)
//DPRINT(i); DPRINT(": "); DPRINTLN(segmentEnableBits[i],BIN);
}
// Precompute cumulative "wipe" animation masks (animationMode 6 / the "up->down->up" reveal
// used when a digit changes). Each stage progressively adds more segments in a fixed visual
// order (a -> b+f -> g -> e+c -> d), i.e. top segment, then the two middle-height segments,
// then the center bar, then the two lower-middle segments, then the bottom segment --
// roughly mimicking a wipe sweeping down the 7-segment glyph.
animationMaskBits[0] = uint32_t(1<<segmentEnablePins[0]); //a
animationMaskBits[1] = animationMaskBits[0] | uint32_t(1<<segmentEnablePins[1]) | uint32_t(1<<segmentEnablePins[5]); //bf
animationMaskBits[2] = animationMaskBits[1] | uint32_t(1<<segmentEnablePins[6]); //g
animationMaskBits[3] = animationMaskBits[2] | uint32_t(1<<segmentEnablePins[4]) | uint32_t(1<<segmentEnablePins[2]); //ec
animationMaskBits[4] = animationMaskBits[3] | uint32_t(1<<segmentEnablePins[3]); //d
for (int i=0;i<5;i++) {
animationMaskBits[i] = ~animationMaskBits[i]; //invert bits -- stored inverted so writeDisplay() can apply them with a plain AND (val &= mask) to blank out the not-yet-revealed segments
//DPRINTLN(animationMaskBits[i],HEX);
}
DPRINTLN("--- Generating digit pins bitmap ---");
for (int i=0;i<maxDigits;i++) {
digitEnableBits[i] = uint32_t(1 << digitEnablePins[i]); //one-hot bit for each tube's grid/anode-enable output
//DPRINT(i); DPRINT(": "); DPRINTLN( digitEnableBits[i],BIN);
}
DPRINTLN("---- Generated Character / Pins table -----");
for (int i=0;i<MAXCHARS;i++) {
out = 0;
//DPRINT(i); DPRINT(": ");
//DPRINT(charDefinition[i],BIN); //DPRINT(" = ");
for (int j=0;j<=7;j++) //from a to g (j=0..6 are segments a..g, j=7 is DP; bit(7-j) walks charDefinition MSB->LSB to match that ordering)
if ((charDefinition[i] & 1<<(7-j)) != 0) {
out = out | segmentEnableBits[j]; //DPRINT("1");
}
//else DPRINT("0");
//DPRINT(" >> ");
charTable[i] = out; //final per-glyph MAX6921 output bitmap, ready to OR with digitEnableBits[pos] in writeDisplay()
//DPRINTLN(charTable[i],BIN);
} //end for
}
void clearTubes() {
// Only asserts BLANK (forces all MAX6921 outputs off) -- it does NOT clear the shift
// register/latch contents or the digit[]/newDigit[] buffers. The stale frame stays latched
// in the chip and will reappear instantly the moment BLANK is deasserted again (e.g. next
// writeDisplay() ISR tick), so this is a cheap/fast "go dark" rather than a true reset.
digitalWrite(PIN_BL,HIGH);
}
// Intentionally empty: this driver's entire refresh/multiplex logic runs inside the
// hardware-timer ISR (writeDisplay()), so there is nothing left for a synchronous single-shot
// write to do. The function still needs to exist because the core file (ESP32_UniClock2.ino)
// calls writeDisplaySingle() unconditionally from several places (e.g. after changing a setting).
void writeDisplaySingle() {}
#endif