278 lines
14 KiB
Arduino
278 lines
14 KiB
Arduino
 
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/*==============================================================================
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MM5450.ino - driver for the MM5450 (National Semi / clone) LED segment driver IC.
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Hardware: MM5450 is a 34-output constant-current LED sink driver with a
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simple synchronous serial input (start bit + 34 data bits, latched with a
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LE/latch-enable pulse). It has NO on-chip digit multiplexing and NO
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brightness/intensity register - unlike MAX7219. In this board design a
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single MM5450 is time-shared between TWO groups of 4x 7-segment+DP digits
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(32 segment lines + 2 "side enable" lines = 34 outputs), and brightness is
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produced entirely in software via PWM (see writeDisplay()/PWMrefresh below),
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driven from the periodic hardware-timer ISR started by startTimer().
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Wiring/protocol: DATA/CLK/LE are bit-banged (not hardware SPI) directly via
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ESP8266 GPIO-set/clear peripheral registers for speed, because writeBits()
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runs inside the timer ISR. Bits are shifted out in ascending bitBuffer[]
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index order (index 0 first), each element corresponding 1:1 to one MM5450
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output (index = output pin number as defined by the MM5450 datasheet,
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1..34), with bitBuffer[0] used as the fixed "start bit" required by the
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chip's serial protocol to frame the following 34 data bits.
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Used by (see clocks.h): CLOCK_11 - "8266 LED Clock with MM5450 chip"
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(clocks.h defines MM5450 only inside the #ifdef CLOCK_11 block).
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==============================================================================*/
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#ifdef MM5450
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char tubeDriver[] = "MM5450";
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int maxDigits = 6;
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//Fill this table with the pin numbers of the MM5450 chip!
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// Maps [digit-group 0..3][segment a..g,DP] -> MM5450 output pin number (1..34).
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// Digit groups 0,1 belong to display "side" 0, groups 2,3 belong to "side" 1
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// (see sideEnablePins[] and the side-switching logic in writeDisplay()).
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byte segmentEnablePins[4][8] = {
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{16, 15, 14, 13, 12, 11, 10, 9}, //segment enable pins of MM5450 (a,b,c,d,e,f,g,DP)
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{8, 7, 6, 5, 4, 3, 2, 1},
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{17, 18, 19, 20, 21, 22, 23, 24},
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{25, 26, 27, 28, 29, 30, 31, 32}
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};
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/* Old version - kept for reference only, NOT compiled (different pin-to-output mapping,
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presumably from an earlier PCB revision with different MM5450 output wiring).
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byte segmentEnablePins[4][8] = {
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{25,26,27,28,29,30,31,32}, //segment enable pins of MM5450 (a,b,c,d,e,f,g,DP)
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{17,18,19,20,21,22,23,24},
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{9,10,11,12,13,14,15,16},
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{1,2,3,4,5,6,7,8}
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};
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*/
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byte sideEnablePins[] = {34, 33}; //enable pins for the two groups of 4 digits (2x4 LEDs)
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// sideEnablePins[0] = MM5450 output 34 = enable line for "side 0" (digit groups 0,1)
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// sideEnablePins[1] = MM5450 output 33 = enable line for "side 1" (digit groups 2,3)
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// Only one side's enable line is driven HIGH at a time -> the two 4-digit
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// groups share the same 32 segment lines and are multiplexed in time.
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//MM5450 control pins (GPIO numbers - see clocks.h D5pin/D6pin/etc for the NodeMCU Dx aliases:
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// GPIO14=D5, GPIO12=D6, GPIO13=D7, GPIO15=D8)
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#define PIN_LE 14 // D5 Shift Register Latch Enable
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#define PIN_CLK 12 // D6 Shift Register Clock
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#define PIN_DATA 13 // D7 Shift Register Data
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#define PIN_BR 15 // D8 Shift Register Brightness (chip-enable/blank output, active HIGH)
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// Bitmasks for the same pins, used with WRITE_PERI_REG(PIN_OUT_SET/CLEAR, ...) for fast
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// direct GPIO register access inside the ISR (digitalWrite() is too slow/has too much
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// call overhead to meet the tight bit-banging timing below).
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#define PIN_LE_BIT 1<<14 // D5 Shift Register Latch Enable
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#define PIN_CLK_BIT 1<<12 // D6 Shift Register Clock
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#define PIN_DATA_BIT 1<<13 // D7 Shift Register Data
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#define PIN_BR_BIT 1<<15 // D8 Shift Register Brightness
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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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#define MAXCHARS sizeof(charDefinition) // (currently unused in this file - kept for reference/consistency with other drivers)
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int PWMrefresh = 10000; //usec, Multiplex time period (one full ON+OFF brightness cycle). Greater value => slower multiplex/PWM frequency
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// PWM_min/PWM_max bound the ON-time portion of PWMrefresh: since the MM5450 has no
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// hardware intensity register, brightness is entirely software PWM - writeDisplay()
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// re-arms the hw timer with a shorter or longer "ON" interval depending on the
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// requested brightness (see PWMtimeBrightness below).
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int PWM_min = 500;
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int PWM_max = 10000;
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//int PWMtiming[11] = {0,500,800,1200,2000,2500,3000,4500,6000,8000,10000};
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// bitBuffer holds the full 34-bit MM5450 serial frame plus its leading start bit
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// (bitBuffer[0] = start bit, bitBuffer[1..34] = one byte per output pin, 0/1 = LED off/on).
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// One array element is used per bit (not packed) to make indexing by MM5450 pin number
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// trivial for writeBits(); size 36 leaves a little headroom beyond the 35 bits actually sent.
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byte bitBuffer[36];
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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("MM5450 - Setup pins...");
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pinMode(PIN_LE, OUTPUT); regPin(PIN_LE, "PIN_LE");
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pinMode(PIN_BR, OUTPUT); regPin(PIN_BR, "PIN_BR");
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pinMode(PIN_DATA, OUTPUT); regPin(PIN_DATA, "PIN_DATA");
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pinMode(PIN_CLK, OUTPUT); regPin(PIN_CLK, "PIN_CLK");
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digitalWrite(PIN_BR, HIGH); //brightness
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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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startTimer(); // arms the periodic hw timer -> writeDisplay() becomes the multiplex/PWM ISR
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}
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// Bit-bangs one full 35-bit frame (start bit + 34 output bits) into the MM5450 shift
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// register and latches it. Runs inside the timer ISR (called from writeDisplay()), so it
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// uses direct GPIO SET/CLEAR peripheral-register writes instead of digitalWrite() - the
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// latter's call/pin-lookup overhead would blow the tight clock pulse widths needed here.
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void ICACHE_RAM_ATTR writeBits() {
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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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//noInterrupts(); // not needed: this code already runs inside the timer ISR itself
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WRITE_PERI_REG( PIN_OUT_CLEAR, PIN_LE_BIT ); //DATA_ENABLE - LE must be LOW while shifting data in
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for (int t = 0; t < 5; t++) asm volatile ("nop"); //100nsec
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for (int i = 0; i < 36; i++) { // shift bitBuffer out LSB-index-first (index 0 = start bit, sent first)
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if (bitBuffer[i]) {
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WRITE_PERI_REG( PIN_OUT_SET, PIN_DATA_BIT ); //digitalWrite(PIN_DATA,HIGH);
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}
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else {
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WRITE_PERI_REG( PIN_OUT_CLEAR, PIN_DATA_BIT ); //digitalWrite(PIN_DATA,LOW);
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}
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for (int t = 0; t < 12; t++) asm volatile ("nop"); //300nsec - data setup time before clock edge
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WRITE_PERI_REG( PIN_OUT_SET, PIN_CLK_BIT ); // MM5450 samples DATA on this rising CLK edge
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for (int t = 0; t < 12; t++) asm volatile ("nop"); //300nsec
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WRITE_PERI_REG( PIN_OUT_CLEAR, PIN_CLK_BIT );
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for (int t = 0; t < 12; t++) asm volatile ("nop"); //300nsec
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} //end for
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WRITE_PERI_REG( PIN_OUT_SET, PIN_LE_BIT ); // rising edge on LE latches the shifted-in frame to the outputs
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//interrupts();
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}
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// Main multiplex/PWM ISR, attached to the ESP8266 hw timer1 by startTimer().
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// timer1 is configured TIM_SINGLE (one-shot), so this handler must re-arm itself via
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// timer1_write() at the very end of every call - the display refresh rate/PWM duty
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// cycle is entirely driven by how long each re-armed interval is (see 'timer' below).
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// Each call does ONE of: (a) blank the display for the computed OFF duration (brightness
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// PWM low phase), or (b) blank for the ON duration but first shift out a fresh frame for
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// whichever "side" (group of 4 digits) is up next, alternating sides on every ON call.
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void ICACHE_RAM_ATTR writeDisplay() { // Writes to the MM5450 driver for LEDS
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static volatile int timer = PWMrefresh;
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static volatile boolean state = true; // true = ON phase of the PWM cycle, false = OFF phase
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static volatile int brightness;
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static int PWMtimeBrightness;
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static volatile uint32_t val;
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static volatile byte pos = 0;
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static byte side = 0;
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byte num = 0;
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if (EEPROMsaving) { //stop refresh, while EEPROM write is in progress!
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// Flash writes on ESP8266 briefly disable interrupts/stall the CPU; touching the
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// display bus during that window could corrupt the SPI-like bit-bang timing, so we
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// just keep re-arming the timer with a fixed period and skip the actual refresh.
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timer1_write(PWMrefresh);
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return;
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}
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intCounter++;
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brightness = displayON ? prm.dayBright : prm.nightBright;
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if (brightness > MAXBRIGHTNESS) brightness = MAXBRIGHTNESS; //only for safety
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if (autoBrightness && displayON) {
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// Ambient-light (lx) driven brightness: brighter room -> longer ON time within PWMrefresh
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PWMtimeBrightness = max(PWM_min, PWM_max * lx / MAXIMUM_LUX);
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}
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else
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// Manual brightness setting (0..MAXBRIGHTNESS) mapped linearly onto the ON-time window
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PWMtimeBrightness = max(PWM_min, PWM_max * brightness / MAXBRIGHTNESS);
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if ((!autoBrightness) && (brightness == MAXBRIGHTNESS))
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// At max manual brightness PWMtimeBrightness == PWMrefresh, so the OFF phase would be
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// ~0us; forcing state=true here keeps the ISR permanently in the ON branch instead of
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// wastefully toggling into a near-zero-length OFF phase every other call.
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state = true;
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if (state) { //ON state
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timer = PWMtimeBrightness;
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timerON = timer;
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timerOFF = PWMrefresh - PWMtimeBrightness;
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}
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else { //OFF state
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timer = PWMrefresh - PWMtimeBrightness;
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}
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if (timer < 500) timer = 500; //safety only... (avoid re-arming the hw timer with too short/zero an interval)
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if ( (brightness == 0) || (!state) || (!radarON)) { //OFF state, blank digit
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WRITE_PERI_REG( PIN_OUT_CLEAR, PIN_BR_BIT ); //OFF - BR pin blanks all MM5450 outputs regardless of shift-register content
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// radarON reflects presence-detection (radar/PIR): when nobody is around the display
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// is blanked here (power saving / tube-life) without touching the multiplex state.
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}
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else { //ON state
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WRITE_PERI_REG( PIN_OUT_SET, PIN_BR_BIT ); //ON
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memset(bitBuffer, 0, sizeof(bitBuffer)); //clear array
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bitBuffer[0] = 1; //starting bit required to frame the 34 data bits (see MM5450 datasheet)
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bitBuffer[sideEnablePins[side]] = 0;
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writeBits(); // 1st transfer: push an all-blank frame (except start bit) so BOTH sides are
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// momentarily off before the new side's segments are shifted in - avoids
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// ghosting/cross-talk between the outgoing and incoming digit group.
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for (int t = 0; t < 100; t++) asm volatile ("nop"); //clear display and wait between switching the two sides
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bitBuffer[sideEnablePins[side]] = 0; //disable old side..
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// NOTE: bitBuffer was just memset to 0 a few lines above and this index was already
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// cleared before the previous writeBits() call, so this re-assignment is a redundant
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// no-op (POSSIBLE dead/duplicated code - likely meant to clear something else, e.g.
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// the *other* side, but 'side' has not been toggled yet at this point).
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if (side == 0) side = 1; else side = 0; //change side...
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for (int i = 0; i < 4; i++) {
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pos = 7 - (4 * side + i);
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// POSSIBLE BUG: pos always ranges 0..7 (8 digit positions) regardless of maxDigits
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// (=6 above). digit[6] and digit[7] are never written by the core display-update
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// logic when maxDigits==6, and being plain (non-initialized-to-BLANK) globals they
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// default to 0 -> segment pattern for '0'. If the physical PCB for CLOCK_11 really
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// only has 6 digits wired, positions 6/7 are presumably just unused MM5450 outputs
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// (harmless); if it has 8 digits, the top 2 would never be updated by the clock logic.
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num = digit[pos];
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//if (animMask[pos]>0) val &= animationMaskBits[animMask[pos]-1]; //animationMode 6, mask characters from up to down and back
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// (wipe/mask animation support - referenced 'val' and 'animationMaskBits' are unused/
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// undefined in this file, so this feature is not implemented for the MM5450 driver)
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for (int j = 0; j <= 7; j++) //from a to g
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if ((charDefinition[num] & 1 << (7 - j)) != 0) {
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bitBuffer[segmentEnablePins[i][j]] = 1;
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}
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if (digitDP[pos]) bitBuffer[segmentEnablePins[i][7]] = 1; //Decimal Point
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} //end for
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bitBuffer[sideEnablePins[side]] = 1; //enable new side
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writeBits(); // 2nd transfer: actual segment data + new side's enable bit
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} //end else ON
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state = !state;
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timer1_write(timer); // re-arm the one-shot hw timer for the next ON or OFF phase
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}
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// Both required by the common driver interface but intentionally no-ops here: this driver
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// does all display updates from the writeDisplay() ISR (brightness PWM + side multiplex
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// depend on continuous timer-driven refresh), so there is nothing useful for a one-shot
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// blank (clearTubes) or a one-shot blocking full-frame write (writeDisplaySingle) to do -
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// the next ISR tick will simply pick up the current digit[]/digitDP[] contents.
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void clearTubes() {}
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void writeDisplaySingle() {}
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#endif
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