diff --git a/ports/samd/mcu/samd21/clock_config.c b/ports/samd/mcu/samd21/clock_config.c
index 630b5c0a4a..d3c8c71995 100644
--- a/ports/samd/mcu/samd21/clock_config.c
+++ b/ports/samd/mcu/samd21/clock_config.c
@@ -166,7 +166,7 @@ void init_clocks(uint32_t cpu_freq) {
     // GCLK0: 48MHz, source: DFLL48M or FDPLL96M, usage: CPU
     // GCLK1: 32kHz, source: XOSC32K or OSCULP32K, usage: FDPLL96M reference
     // GCLK2: 1-48MHz, source: DFLL48M, usage: Peripherals
-    // GCLK3: 1Mhz,  source: DFLL48M, usage: us-counter (TC4/TC5)
+    // GCLK3: 2Mhz,  source: DFLL48M, usage: us-counter (TC4/TC5)
     // GCLK4: 32kHz, source: XOSC32K, if crystal present, usage: DFLL48M reference
     // GCLK5: 48MHz, source: DFLL48M, usage: USB
     // GCLK8: 1kHz,  source: XOSC32K or OSCULP32K, usage: WDT and RTC
@@ -291,8 +291,8 @@ void init_clocks(uint32_t cpu_freq) {
 
     set_cpu_freq(cpu_freq);
 
-    // Enable GCLK output: 1MHz on GCLK3 for TC4
-    GCLK->GENDIV.reg = GCLK_GENDIV_ID(3) | GCLK_GENDIV_DIV(48);
+    // Enable GCLK output: 2MHz on GCLK3 for TC4
+    GCLK->GENDIV.reg = GCLK_GENDIV_ID(3) | GCLK_GENDIV_DIV(24);
     GCLK->GENCTRL.reg = GCLK_GENCTRL_GENEN | GCLK_GENCTRL_SRC_DFLL48M | GCLK_GENCTRL_ID(3);
     while (GCLK->STATUS.bit.SYNCBUSY) {
     }
diff --git a/ports/samd/mphalport.c b/ports/samd/mphalport.c
index 44d1470fc5..d7511e61fb 100644
--- a/ports/samd/mphalport.c
+++ b/ports/samd/mphalport.c
@@ -147,7 +147,7 @@ uint64_t mp_hal_ticks_us_64(void) {
         us64_upper++;
     }
     #if defined(MCU_SAMD21)
-    return ((uint64_t)us64_upper << 32) | us64_lower;
+    return ((uint64_t)us64_upper << 31) | (us64_lower >> 1);
     #elif defined(MCU_SAMD51)
     return ((uint64_t)us64_upper << 28) | (us64_lower >> 4);
     #endif
diff --git a/ports/samd/mphalport.h b/ports/samd/mphalport.h
index d5fc935343..83ccf44222 100644
--- a/ports/samd/mphalport.h
+++ b/ports/samd/mphalport.h
@@ -54,11 +54,7 @@ static inline mp_uint_t mp_hal_ticks_ms(void) {
 }
 
 static inline mp_uint_t mp_hal_ticks_us(void) {
-    #if defined(MCU_SAMD21)
-    return REG_TC4_COUNT32_COUNT;
-    #else
     return (mp_uint_t)mp_hal_ticks_us_64();
-    #endif
 }
 
 #if defined(MCU_SAMD21)