diff --git a/core/esp_timer.c b/core/esp_timer.c
index c2b45a0..9282e26 100644
--- a/core/esp_timer.c
+++ b/core/esp_timer.c
@@ -78,7 +78,7 @@ uint32_t timer_time_to_count(const timer_frc_t frc, uint32_t us, const timer_clk
     }
 }
 
-bool timer_set_frequency(const timer_frc_t frc, uint32_t freq)
+int timer_set_frequency(const timer_frc_t frc, uint32_t freq)
 {
     uint32_t counts = 0;
     timer_clkdiv_t div = timer_freq_to_div(freq);
@@ -86,8 +86,7 @@ bool timer_set_frequency(const timer_frc_t frc, uint32_t freq)
     counts = timer_freq_to_count(frc, freq, div);
     if(counts == 0)
     {
-        printf("ABORT: No counter for timer %u frequency %u\r\n", frc, freq);
-        abort();
+        return -EINVAL;
     }
 
     timer_set_divider(frc, div);
@@ -101,17 +100,17 @@ bool timer_set_frequency(const timer_frc_t frc, uint32_t freq)
         /* assume that if this overflows it'll wrap, so we'll get desired behaviour */
         TIMER(1).ALARM = counts + TIMER(1).COUNT;
     }
-    return true;
+    return 0;
 }
 
-bool timer_set_timeout(const timer_frc_t frc, uint32_t us)
+int _timer_set_timeout_impl(const timer_frc_t frc, uint32_t us)
 {
     uint32_t counts = 0;
     timer_clkdiv_t div = timer_time_to_div(us);
 
     counts = timer_time_to_count(frc, us, div);
     if(counts == 0)
-        return false; /* can't set frequency */
+        return -EINVAL; /* can't set frequency */
 
     timer_set_divider(frc, div);
     if(frc == FRC1)
@@ -123,5 +122,27 @@ bool timer_set_timeout(const timer_frc_t frc, uint32_t us)
         TIMER(1).ALARM = counts + TIMER(1).COUNT;
     }
 
-    return true;
+    return 0;
+}
+
+int timer_set_timeout(const timer_frc_t frc, uint32_t us)
+{
+    uint32_t counts = 0;
+    timer_clkdiv_t div = timer_time_to_div(us);
+
+    counts = timer_time_to_count(frc, us, div);
+    if(counts == 0)
+        return -EINVAL; /* can't set frequency */
+
+    timer_set_divider(frc, div);
+    if(frc == FRC1)
+    {
+        timer_set_load(frc, counts);
+    }
+    else /* FRC2 */
+    {
+        TIMER(1).ALARM = counts + TIMER(1).COUNT;
+    }
+
+    return 0;
 }
diff --git a/core/include/esp/timer.h b/core/include/esp/timer.h
index fc4e6f8..fc74992 100644
--- a/core/include/esp/timer.h
+++ b/core/include/esp/timer.h
@@ -10,6 +10,7 @@
 #define _ESP_TIMER_H
 
 #include <stdbool.h>
+#include <errno.h>
 #include "esp/timer_regs.h"
 #include "esp/interrupts.h"
 
@@ -159,9 +160,9 @@ uint32_t timer_time_to_count(const timer_frc_t frc, uint32_t us, const timer_clk
    Does not start/stop the timer, you have to do this manually via
    timer_set_run.
 
-   Returns true on success, false if given frequency could not be set.
+   Returns 0 on success, or -EINVAL if given frequency could not be set.
 */
-bool timer_set_frequency(const timer_frc_t frc, uint32_t freq);
+int timer_set_frequency(const timer_frc_t frc, uint32_t freq);
 
 /* Sets the timer for a oneshot interrupt in 'us' microseconds.
 
@@ -176,9 +177,9 @@ bool timer_set_frequency(const timer_frc_t frc, uint32_t freq);
    also disable FRC1 in the timer interrupt handler by calling
    timer_set_run(TIMER_FRC1, false);
 
-   Returns true if the timeout was successfully set.
+   Returns 0 on success, or -EINVAL if the given timeout could not be set.
 */
-bool timer_set_timeout(const timer_frc_t frc, uint32_t us);
+int timer_set_timeout(const timer_frc_t frc, uint32_t us);
 
 #ifdef	__cplusplus
 }