diff --git a/cpu/pico-rv32/Makefile.pico-rv32 b/cpu/pico-rv32/Makefile.pico-rv32
index cf6e55dd6..0f20936e5 100644
--- a/cpu/pico-rv32/Makefile.pico-rv32
+++ b/cpu/pico-rv32/Makefile.pico-rv32
@@ -22,7 +22,7 @@ STRIP    = riscv32-unknown-elf-strip
 ifdef WERROR
 CFLAGSWERROR=-Werror
 endif
-CFLAGSNO = -Wall -g \
+CFLAGSNO = -Wall -march=RV32IXcustom -g \
     -I$(CONTIKI)/platform/$(TARGET) \
     -I. -I$(CONTIKI)/core -I$(CONTIKI_CPU)
 CFLAGS  += $(CFLAGSNO) -Os
diff --git a/cpu/pico-rv32/dev/clock.c b/cpu/pico-rv32/dev/clock.c
index 58e131ec7..af4374710 100644
--- a/cpu/pico-rv32/dev/clock.c
+++ b/cpu/pico-rv32/dev/clock.c
@@ -55,29 +55,40 @@
  * It is defined through CONF_CLOCK_SECOND in the contiki-conf.h for
  * each platform.
  * The usual AVR defaults are 128 or 125 ticks per second, counting a
- * prescaled CPU clock using the 8 bit timer0.
+ * prescaled CPU clock using the 8 bit timer0. We use the same in the
+ * timer interrupt: 1/128 second ticks, this can be changed by modifying
+ * CLOCK_TIMER_PERIOD below.
  * 
  * clock_time_t is usually declared by the platform as an unsigned 16
  * bit data type, thus intervals up to 512 or 524 seconds can be
  * measured with ~8 millisecond precision.
  * For longer intervals the 32 bit clock_seconds() is available.
+ * We directly use the 64-bit cycle counter provided by the CPU.
  */
 #include "sys/clock.h"
 #include "sys/etimer.h"
+#include "icosoc.h"
 
 #include <stdio.h> // FIXME
 
+// 1/128 second ticks
+#define CLOCK_TIMER_PERIOD (F_CPU >> 7)
+
 static volatile clock_time_t count;
 unsigned long offset;
-long sleepseconds;
+
+void irq_handler(uint32_t irq_mask, uint32_t *regs);
 
 /*---------------------------------------------------------------------------*/
 /**
- * No need to init
+ * Initialize interrupt handler
  */
     void
 clock_init(void)
 {
+    icosoc_irq(irq_handler);
+    icosoc_maskirq(0);
+    icosoc_timer(CLOCK_TIMER_PERIOD);
 }
 /*---------------------------------------------------------------------------*/
 /**
@@ -147,5 +158,29 @@ clock_adjust_ticks(clock_time_t howmany)
 {
 }
 
+/** \brief irq handler
+ * for running interrupts every 1/128 second.
+ */
+
+void
+irq_handler(uint32_t irq_mask, uint32_t *regs)
+{
+    // timer interrupt
+    if (irq_mask & 1) {
+        // FIXME: Want to call rtimer_run_next();
+        icosoc_timer(CLOCK_TIMER_PERIOD);
+        if(etimer_pending()) {
+            etimer_request_poll();
+        }
+    }
+    // SBREAK, ILLINS or BUSERROR
+    if (irq_mask & 4) {
+        printf("Bus Error!\n");
+    }
+    // Can we distinguish ILLINS and SBREAK?
+    if (irq_mask & 2) {
+        icosoc_sbreak();
+    }
+}
 /** @} */
 /** @} */
diff --git a/cpu/pico-rv32/rtimer-arch.c b/cpu/pico-rv32/rtimer-arch.c
index dee4481b8..d47585429 100644
--- a/cpu/pico-rv32/rtimer-arch.c
+++ b/cpu/pico-rv32/rtimer-arch.c
@@ -45,9 +45,11 @@
 void
 rtimer_arch_init(void)
 {
+    printf ("rtimer_arch_init called\n");
 }
 /*---------------------------------------------------------------------------*/
 void
 rtimer_arch_schedule(rtimer_clock_t t)
 {
+    printf ("Scheduling timer: %d\n", t);
 }
diff --git a/cpu/pico-rv32/rtimer-arch.h b/cpu/pico-rv32/rtimer-arch.h
index 272dece0c..311200746 100644
--- a/cpu/pico-rv32/rtimer-arch.h
+++ b/cpu/pico-rv32/rtimer-arch.h
@@ -38,6 +38,4 @@
 #define RTIMER_ARCH_SECOND F_CPU
 
 #define rtimer_arch_now() (clock_time ())
-
-void rtimer_arch_sleep(rtimer_clock_t howlong);
 #endif /* RTIMER_ARCH_H_ */
diff --git a/examples/osd/ico-wallclock-time/.gitignore b/examples/osd/ico-wallclock-time/.gitignore
index de3098d4b..64ebf92f8 100644
--- a/examples/osd/ico-wallclock-time/.gitignore
+++ b/examples/osd/ico-wallclock-time/.gitignore
@@ -4,7 +4,9 @@ icosoc.mk
 icosoc.pcf
 icosoc.v
 icosoc.ys
+icosoc.rpt
 wallclock.co
 wallclock.pico-rv32-icoboard
 icosoc.c
 icosoc.h
+testbench.v
diff --git a/examples/osd/ico-wallclock-time/wallclock.c b/examples/osd/ico-wallclock-time/wallclock.c
index f2b57b4cd..9c63bf65a 100644
--- a/examples/osd/ico-wallclock-time/wallclock.c
+++ b/examples/osd/ico-wallclock-time/wallclock.c
@@ -73,10 +73,7 @@ PROCESS (wallclock, "Wallclock Example Server");
 AUTOSTART_PROCESSES(&wallclock);
 
 //#define LOOP_INTERVAL (30 * CLOCK_SECOND)
-//#define LOOP_INTERVAL (3 * CLOCK_SECOND)
-// one more than this will currently hang, probably due to
-// non-implemented etimer callback.
-#define LOOP_INTERVAL (25461)
+#define LOOP_INTERVAL (5 * CLOCK_SECOND)
 
 /*
  * Set led to on or off, we abuse the given pointer to simply carry the
diff --git a/platform/pico-rv32-icoboard/contiki-conf.h b/platform/pico-rv32-icoboard/contiki-conf.h
index 170e0dac7..1d1baa1cf 100644
--- a/platform/pico-rv32-icoboard/contiki-conf.h
+++ b/platform/pico-rv32-icoboard/contiki-conf.h
@@ -42,12 +42,13 @@
 #define CONTIKI_CONF_H_
 
 #include "rv32def.h"
+#include "icosoc.h"
 
 /* Platform name, type, and MCU clock rate */
 #define PLATFORM_NAME  "PicoRV32-icoboard"
 #define PLATFORM_TYPE  PICORV32
 #ifndef F_CPU
-#define F_CPU          2000000ULL
+#define F_CPU          (ICOSOC_CLOCK_FREQ_HZ)
 #endif
 
  /* Clock ticks per second, our timer runs with cpu freq */
diff --git a/platform/pico-rv32-icoboard/contiki-main.c b/platform/pico-rv32-icoboard/contiki-main.c
index 42cee88f6..85efabfc2 100644
--- a/platform/pico-rv32-icoboard/contiki-main.c
+++ b/platform/pico-rv32-icoboard/contiki-main.c
@@ -114,6 +114,7 @@ uint16_t *p=&__bss_end;
     } while (p<SP-10); //don't overwrite our own stack
 }
 #endif
+  clock_init();
 
   PRINTA("\n*******Booting %s*******\n",CONTIKI_VERSION_STRING);