[Hacky Holidays] The Pixel Clock

projects/the-pixel-clock/README.md

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+---
+name: "Siddhant Kameswar"
+slack_handle: "@grimsteel"
+github_handle: "@grimsteel"
+tutorial: # Link to the tutorial if you used one
+wokwi: # Wokwi doesn't support the CH552 (and my firmware is highly dependent on CH552-specific registers and 8051 ASM.)
+---
+
+# The Pixel Clock
+
+<!-- Describe your board in 2-3 sentences. What are you making? What will it do? -->
+
+This is a clock-shaped holiday ornament (which unfortunately cannot function as a clock). It's powered by 2 LIR2032 batteries, and runs on an 8051 CH552 MCU. It has a buzzer which can be used to play songs, with the 8 neopixels flashing in sync.
+
+<!-- How much is it going to cost? -->
+
+## Cost
+
+$31.72 + $18.15 shipping - $9.00 coupon = **$40.87**
+
+<!-- Tell us a little bit about your design process. What were some challenges? What helped? ***Totally optional*** -->
+
+## Design Process
+
+There's not much information on the CH552 online, so figuring out what its voltage/current requirements and capabilities were as well as figuring out how to program it was difficult.

projects/the-pixel-clock/firmware/.gitignore

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+*.asm
+*.lst
+*.mem
+*.rel
+*.rst
+*.sym
+*.adb
+*.lk
+*.map
+*.mem
+*.ihx
+*.hex
+*.bin
+
+.cache/
+compile_commands.json

projects/the-pixel-clock/firmware/Makefile

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+# This Makefile is adapted from https://github.com/Blinkinlabs/ch554_sdcc
+
+TARGET=pixel-clock
+C_FILES := $(wildcard *.c) $(CH554_SDCC_PATH)/debug.c
+
+
+#######################################################
+
+# toolchain
+CC = sdcc
+OBJCOPY = objcopy
+PACK_HEX = packihx
+WCHISP ?= wchisptool -g -f
+
+#######################################################
+
+FREQ_SYS ?= 6000000 # 6 MHz
+
+XRAM_SIZE ?= 0x0400
+
+XRAM_LOC ?= 0x0000
+
+CODE_SIZE ?= 0x3800
+
+CFLAGS := -V -mmcs51 --model-small \
+	--xram-size $(XRAM_SIZE) --xram-loc $(XRAM_LOC) \
+	--code-size $(CODE_SIZE) \
+	-I$(CH554_SDCC_PATH) -DFREQ_SYS=$(FREQ_SYS) \
+	$(EXTRA_FLAGS)
+
+LFLAGS := $(CFLAGS)
+
+RELS := $(C_FILES:.c=.rel)
+
+print-%  : ; @echo $* = $($*)
+
+%.rel : %.c
+	$(CC) -c $(CFLAGS) $<
+
+# Note: SDCC will dump all of the temporary files into this one, so strip the paths from RELS
+# For now, get around this by stripping the paths off of the RELS list.
+
+$(TARGET).ihx: $(RELS)
+	$(CC) $(notdir $(RELS)) $(LFLAGS) -o $(TARGET).ihx
+
+$(TARGET).hex: $(TARGET).ihx
+	$(PACK_HEX) $(TARGET).ihx > $(TARGET).hex
+
+$(TARGET).bin: $(TARGET).ihx
+	$(OBJCOPY) -I ihex -O binary $(TARGET).ihx $(TARGET).bin
+
+flash: $(TARGET).bin pre-flash
+	$(WCHISP) $(TARGET).bin
+
+.DEFAULT_GOAL := all
+all: $(TARGET).bin $(TARGET).hex
+
+clean:
+	rm -f \
+	$(notdir $(RELS:.rel=.asm)) \
+	$(notdir $(RELS:.rel=.lst)) \
+	$(notdir $(RELS:.rel=.mem)) \
+	$(notdir $(RELS:.rel=.rel)) \
+	$(notdir $(RELS:.rel=.rst)) \
+	$(notdir $(RELS:.rel=.sym)) \
+	$(notdir $(RELS:.rel=.adb)) \
+	$(TARGET).lk \
+	$(TARGET).map \
+	$(TARGET).mem \
+	$(TARGET).ihx \
+	$(TARGET).hex \
+	$(TARGET).bin

projects/the-pixel-clock/firmware/main.c

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+#ifndef bool
+#define bool int
+#endif
+
+#include "ch554.h"
+#include "debug.h"
+#include "programs.h"
+
+#define P1 0x90
+#define P3 0xB0
+
+// setup buttons
+
+// BTN1: P3.1
+// BTN2: P1.4
+#define BTN1_PIN 1
+#define BTN2_PIN 4
+SBIT(BTN1, P3, BTN1_PIN);
+SBIT(BTN2, P1, BTN2_PIN);
+
+// BUZ: P1.5
+#define BUZ_PIN 5
+SBIT(BUZ, P1, BUZ_PIN);
+
+// WS2812B: P1.1
+#define WS2812B_PIN 1
+#define NUM_WS2812B 8
+SBIT(WS2812B, P1, WS2812B_PIN);
+
+// [0, 256)
+#define WS2812B_BRIGHTNESS 51
+
+// GRB, in order
+uint8_t ws2812b_data[NUM_WS2812B * 3];
+
+// Timer frequency in hertz (6 MHz / 12)
+#define TIMER_FREQUENCY 500000
+#define HALF_TIMER_FREQUENCY 250000
+
+uint16_t timer_ticks_start;
+uint32_t toggle_count;
+// this serves as the current time.
+// 1 "unit" of timer1_overflows is 0.5ms
+volatile uint32_t timer1_overflows = 0;
+uint32_t last_button1_press = 0;
+uint32_t last_button2_press = 0;
+volatile uint8_t current_idx = 0;
+
+void next_program_item();
+
+// PWM timer interrupt
+void timer0_interrupt(void) __interrupt(INT_NO_TMR0) {
+  // one-half cycle has elapsed
+  TL0 = timer_ticks_start & 0xff;
+  TH0 = timer_ticks_start >> 8;
+
+  if (toggle_count-- > 0) {
+    // toggle pin
+    BUZ = !BUZ;
+  } else {
+    // turn off
+    BUZ = 0;
+    // stop the timer, disable interrupt
+    TMOD &= ~bT0_M0;
+    TR0 = 0;
+
+    // wait 100ms before next item
+    mDelaymS(100);
+    next_program_item();
+  }
+}
+
+// Main timer interrupt
+void timer1_interrupt(void) __interrupt(INT_NO_TMR1) { timer1_overflows++; }
+
+inline void btn1_press() {}
+inline void btn2_press() {}
+
+// GPIO interurpt
+void gpio_interrupt(void) __interrupt(INT_NO_GPIO) {
+  if (!BTN1) {
+    // if last_button1_press < timer1_overflows, the program has been running for 25 days, and we overflowed the unsigned int
+    if (last_button1_press < timer1_overflows && timer1_overflows - last_button1_press >= 20) {
+      btn1_press();
+    }
+    last_button1_press = timer1_overflows;
+  }
+
+  if (!BTN2) {
+    if (last_button2_press < timer1_overflows && timer1_overflows - last_button2_press >= 20) {
+      btn2_press();
+    }
+    last_button2_press = timer1_overflows;
+  }
+}
+
+// PWM - 50% duty cycle
+// Builtin PWM is too fast for audible tones
+// Duration is measured in 16th notes (250ms)
+void tone(uint16_t frequency_hz, uint8_t duration) {
+  // already playing a tone
+  if (TR0 == 1) return;
+
+  // TODO: Higher frequencies may be able to use a faster clock (bT0_CLK, bTMR_CLK)
+
+  ET0 = 1; // timer0 interrupt
+  TMOD |= bT0_M0; // 16 bit timer0
+
+  // Adapted from arduino tone() code
+  // TIMER_FREQUENCY / frequency_hz returns number of ticks for a full cycle
+  // Because this is 50% duty cycle, divide by 2 for number of ticks for each "high" or each "low"
+  // We will start counting at this value, and go to 0xffff
+  // idk what the +1 is for
+  timer_ticks_start = 0xffff - (uint16_t) ((uint32_t) (HALF_TIMER_FREQUENCY) / frequency_hz) + 1;
+  // frequency * duration = number of full cycles
+  // * 2 = number of toggles
+  // / 1000 because ms
+  // toggle_count = (uint32_t) (frequency_hz * duration_ms) / 1000 * 2;
+  // optimized version: measure duration as 1/4 second
+  toggle_count = frequency_hz * duration >> 1;
+
+  // Set the timer
+  TL0 = timer_ticks_start & 0xff;
+  TH0 = timer_ticks_start >> 8;
+
+  TR0 = 1; // begin timer
+}
+
+void ws2812b_write() {
+  // disable interrupts (time sensitive!)
+  E_DIS = 1;
+  for (uint8_t i = 0; i < NUM_WS2812B * 3; i++) {
+    // TIMINGS AT 6MHz (tolerance 150 ns aka 1 clock cycle)
+    // T1H = 0.8 us --> 4-5 clock cycles
+    // T1L = 0.45 us --> 2-3 clock cycles
+    // T0H = 0.4 us -> 2-3 clock cycles
+    // T0L = 0.85 us --> 5-6 clock cycles
+    // The low times don't _really_ matter - only the high times matter for distinguishing between 0s and 1s
+    // RESET TIME: > 50 us --> 300 clock cycles
+    // Total time: 7/8 clock cycles
+    // TODO: Tune with a logic analyzer
+    __asm
+    mov a, r7 ; i is stored in r7
+    add a, #_ws2812b_data ; ws2812b_data[i]
+    mov r6, #8 ; eight bits
+01$:            ; --- loop
+    rlc a           ; 1 cycle
+    setb _WS2812B   ; 1 cycle - T1H begin + T0H begin + T0L end (2 + 1 + 2 + 1) + T1L end (1 + 2 + 1)
+    nop             ; 1 cycle
+    mov _WS2812B, c ; 2 cycles - T0H end (1 + 1) + T0L begin
+    clr _WS2812B    ; 1 cycle - T1H end (1 + 1 + 2) + T1L begin
+    djnz r6, 01$    ; 2 cycles
+    __endasm;
+  }
+  // re-enable interrupts
+  E_DIS = 0;
+}
+
+// Hues is an array of length NUM_WS2812B
+void ws2812b_set_hues(uint16_t *hues) {
+  for (int i = 0; i < NUM_WS2812B; i++) {
+    uint16_t hue = hues[i];
+    uint8_t r = 0, g = 0, b = 0;
+    uint8_t sector = hue / 60;
+    switch (sector) {
+    case 5: // [300, 360)
+      r = WS2812B_BRIGHTNESS;
+      b = WS2812B_BRIGHTNESS * 6 - WS2812B_BRIGHTNESS * hue / 60;
+      break;
+    case 0: // [0, 60)
+      r = WS2812B_BRIGHTNESS;
+      g = WS2812B_BRIGHTNESS * hue / 60;
+      break;
+
+    case 1: // [60, 120)
+      g = WS2812B_BRIGHTNESS;
+      r = WS2812B_BRIGHTNESS * 2 - WS2812B_BRIGHTNESS * hue / 60;
+      break;
+    case 2:
+      g = WS2812B_BRIGHTNESS;
+      b = WS2812B_BRIGHTNESS * hue / 60 - WS2812B_BRIGHTNESS * 2;
+      break;
+
+    case 3:
+      b = WS2812B_BRIGHTNESS;
+      g = WS2812B_BRIGHTNESS * 4 - WS2812B_BRIGHTNESS * hue / 60;
+      break;
+    case 4:
+      b = WS2812B_BRIGHTNESS;
+      r = WS2812B_BRIGHTNESS * hue / 60 - WS2812B_BRIGHTNESS * 4;
+      break;
+    }
+    ws2812b_data[i * 3] = g;
+    ws2812b_data[i * 3 + 1] = r;
+    ws2812b_data[i * 3 + 2] = b;
+  }
+}
+
+void next_program_item() {
+  if (current_idx == PROGRAM1_LENGTH)  {
+    // wait 1 second before repeating
+    current_idx = 0;
+    mDelaymS(1000);
+  }
+  uint16_t hues[NUM_WS2812B];
+  for (int j = 0; j < NUM_WS2812B; j++) {
+    hues[j] = program_1_hues[current_idx];
+  }
+  ws2812b_set_hues(hues);
+  ws2812b_write();
+
+  // buzzer
+  tone(program_1_notes[current_idx], program_1_durations[current_idx]);
+  current_idx++;
+}
+
+void main() {
+  // frequency is default (6MHz)
+  // CfgFsys(); no need for this
+  mDelaymS(5);
+
+  /*// enter safe mode
+  SAFE_MOD = 0x55;
+  SAFE_MOD = 0xAA;
+
+  // setup sleep wake on buttons
+  WAKE_CTRL |= bWAK_P1_4_LO | bWAK_P3_2E_3L; // 3.2 is disconnected
+
+  // exit safe mode
+  SAFE_MOD = 0x00;*/
+
+  mInitSTDIO();
+  UART1Setup();
+
+  // disable all pullups except for 1.2 and 1.3 (clock)
+  P1_DIR_PU &= 0x0C;
+  // disable all except for 3.6 and 3.7 (usb)
+  P3_DIR_PU &= 0xC0;
+
+  // push pull mode
+  P1_MOD_OC &= ~(1 << WS2812B_PIN);
+  // enable pullup
+  P1_DIR_PU |= 1 << WS2812B_PIN;
+
+
+  P1_MOD_OC &= ~(1 << BUZ_PIN);
+  P1_DIR_PU |= 1 << BUZ_PIN;
+  BUZ = 0;
+
+  // configure buttons as high impedance with pullup
+  P1_MOD_OC |= 1 << BTN2_PIN;
+  P1_DIR_PU |= 1 << BTN2_PIN;
+
+  P3_MOD_OC |= 1 << BTN1_PIN;
+  P3_DIR_PU |= 1 << BTN1_PIN;
+
+  // enable interrupts
+  EA = 1;
+  // gpio interrupts
+  IE_GPIO = 1;
+  // gpio edge interrupt mode, enable on 1.4 and 3.1
+  GPIO_IE |= bIE_IO_EDGE | bIE_P1_4_LO | bIE_P3_1_LO;
+
+  ET1 = 1; // timer0 interrupt
+  TMOD |= bT1_M1;// 8 bit timer1 (0.5 ms for each overflow - 256 / (6 MHz / 12) = 512 us)
+  TR1 = 1;
+
+  // start program
+  next_program_item();
+}