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diff --git a/circuitpython/lib/protomatter/src/arch/samd21.h b/circuitpython/lib/protomatter/src/arch/samd21.h
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+++ b/circuitpython/lib/protomatter/src/arch/samd21.h
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+/*!
+ * @file samd21.h
+ *
+ * Part of Adafruit's Protomatter library for HUB75-style RGB LED matrices.
+ * This file contains SAMD21-SPECIFIC CODE.
+ *
+ * Adafruit invests time and resources providing this open source code,
+ * please support Adafruit and open-source hardware by purchasing
+ * products from Adafruit!
+ *
+ * Written by Phil "Paint Your Dragon" Burgess and Jeff Epler for
+ * Adafruit Industries, with contributions from the open source community.
+ *
+ * BSD license, all text here must be included in any redistribution.
+ *
+ */
+
+#pragma once
+
+#if defined(_SAMD21_) || defined(SAMD21) // Arduino, Circuitpy SAMD21 defs
+
+#if defined(ARDUINO) // COMPILING FOR ARDUINO ------------------------------
+
+// g_APinDescription[] table and pin indices are Arduino specific:
+#define _PM_portOutRegister(pin)                                               \
+  &PORT_IOBUS->Group[g_APinDescription[pin].ulPort].OUT.reg
+
+#define _PM_portSetRegister(pin)                                               \
+  &PORT_IOBUS->Group[g_APinDescription[pin].ulPort].OUTSET.reg
+
+#define _PM_portClearRegister(pin)                                             \
+  &PORT_IOBUS->Group[g_APinDescription[pin].ulPort].OUTCLR.reg
+
+#define _PM_portToggleRegister(pin)                                            \
+  &PORT_IOBUS->Group[g_APinDescription[pin].ulPort].OUTTGL.reg
+
+#else // END ARDUINO -------------------------------------------------------
+
+// Non-Arduino port register lookups go here, if not already declared
+// in samd-common.h.
+
+#endif
+
+// CODE COMMON TO ALL ENVIRONMENTS -----------------------------------------
+
+// Initialize, but do not start, timer
+void _PM_timerInit(void *tptr) {
+  static const struct {
+    Tc *tc;         // -> Timer/counter peripheral base address
+    IRQn_Type IRQn; // Interrupt number
+    uint8_t GCM_ID; // GCLK selection ID
+  } timer[] = {
+#if defined(TC0)
+    {TC0, TC0_IRQn, GCM_TCC0_TCC1},
+#endif
+#if defined(TC1)
+    {TC1, TC1_IRQn, GCM_TCC0_TCC1},
+#endif
+#if defined(TC2)
+    {TC2, TC2_IRQn, GCM_TCC2_TC3},
+#endif
+#if defined(TC3)
+    {TC3, TC3_IRQn, GCM_TCC2_TC3},
+#endif
+#if defined(TC4)
+    {TC4, TC4_IRQn, GCM_TC4_TC5},
+#endif
+  };
+#define NUM_TIMERS (sizeof timer / sizeof timer[0])
+
+  Tc *tc = (Tc *)tptr; // Cast peripheral address passed in
+
+  uint8_t timerNum = 0;
+  while ((timerNum < NUM_TIMERS) && (timer[timerNum].tc != tc)) {
+    timerNum++;
+  }
+  if (timerNum >= NUM_TIMERS)
+    return;
+
+  // Enable GCLK for timer/counter
+  GCLK->CLKCTRL.reg = (uint16_t)(GCLK_CLKCTRL_CLKEN | GCLK_CLKCTRL_GEN_GCLK0 |
+                                 GCLK_CLKCTRL_ID(timer[timerNum].GCM_ID));
+  while (GCLK->STATUS.bit.SYNCBUSY == 1)
+    ;
+
+  // Counter must first be disabled to configure it
+  tc->COUNT16.CTRLA.bit.ENABLE = 0;
+  while (tc->COUNT16.STATUS.bit.SYNCBUSY)
+    ;
+
+  tc->COUNT16.CTRLA.reg =       // Configure timer counter
+      TC_CTRLA_PRESCALER_DIV1 | // 1:1 Prescale
+      TC_CTRLA_WAVEGEN_MFRQ |   // Match frequency generation mode (MFRQ)
+      TC_CTRLA_MODE_COUNT16;    // 16-bit counter mode
+  while (tc->COUNT16.STATUS.bit.SYNCBUSY)
+    ;
+
+  tc->COUNT16.CTRLBCLR.reg = TCC_CTRLBCLR_DIR; // Count up
+  while (tc->COUNT16.STATUS.bit.SYNCBUSY)
+    ;
+
+  // Overflow interrupt
+  tc->COUNT16.INTENSET.reg = TC_INTENSET_OVF;
+
+  NVIC_DisableIRQ(timer[timerNum].IRQn);
+  NVIC_ClearPendingIRQ(timer[timerNum].IRQn);
+  NVIC_SetPriority(timer[timerNum].IRQn, 0); // Top priority
+  NVIC_EnableIRQ(timer[timerNum].IRQn);
+
+  // Timer is configured but NOT enabled by default
+}
+
+// Set timer period, initialize count value to zero, enable timer.
+// Timer must be initialized to 16-bit mode using the init function
+// above, but must be inactive before calling this.
+inline void _PM_timerStart(void *tptr, uint32_t period) {
+  Tc *tc = (Tc *)tptr; // Cast peripheral address passed in
+  tc->COUNT16.COUNT.reg = 0;
+  while (tc->COUNT16.STATUS.bit.SYNCBUSY)
+    ;
+  tc->COUNT16.CC[0].reg = period;
+  while (tc->COUNT16.STATUS.bit.SYNCBUSY)
+    ;
+  tc->COUNT16.CTRLA.bit.ENABLE = 1;
+  while (tc->COUNT16.STATUS.bit.SYNCBUSY)
+    ;
+}
+
+// Return current count value (timer enabled or not).
+// Timer must be previously initialized.
+inline uint32_t _PM_timerGetCount(void *tptr) {
+  Tc *tc = (Tc *)tptr; // Cast peripheral address passed in
+  tc->COUNT16.READREQ.reg = TC_READREQ_RCONT | TC_READREQ_ADDR(0x10);
+  while (tc->COUNT16.STATUS.bit.SYNCBUSY)
+    ;
+  return tc->COUNT16.COUNT.reg;
+}
+
+// Disable timer and return current count value.
+// Timer must be previously initialized.
+inline uint32_t _PM_timerStop(void *tptr) {
+  Tc *tc = (Tc *)tptr; // Cast peripheral address passed in
+  uint32_t count = _PM_timerGetCount(tptr);
+  tc->COUNT16.CTRLA.bit.ENABLE = 0;
+  while (tc->COUNT16.STATUS.bit.SYNCBUSY)
+    ;
+  return count;
+}
+
+#endif // END _SAMD21_ || SAMD21