+/* Total ring size in samples */
+#define AO_ADC_RING_SIZE 256
+
+extern uint16_t ao_adc_ring[AO_ADC_RING_SIZE];
+
+#define ao_adc_ring_step(pos,inc) (((pos) + (inc)) & (AO_ADC_RING_SIZE - 1))
+
+extern uint16_t ao_adc_ring_head, ao_adc_ring_remain;
+extern uint16_t ao_adc_running;
+
+/*
+ * Place to start fetching values from
+ */
+static inline uint16_t
+ao_adc_ring_tail(void)
+{
+ return (ao_adc_ring_head - ao_adc_ring_remain) & (AO_ADC_RING_SIZE - 1);
+}
+
+void
+_ao_adc_start(void);
+
+/*
+ * Space available to write ADC values into
+ */
+static inline uint16_t
+_ao_adc_space(void)
+{
+ /* Free to end of buffer? */
+ if (ao_adc_ring_remain <= ao_adc_ring_head)
+ return AO_ADC_RING_SIZE - ao_adc_ring_head;
+
+ /* no, return just the unused entries beyond head */
+ return AO_ADC_RING_SIZE - ao_adc_ring_remain;
+}
+
+static inline uint16_t
+ao_adc_get(uint16_t n)
+{
+ ao_arch_block_interrupts();
+ while (ao_adc_ring_remain < n) {
+ if (!ao_adc_running)
+ _ao_adc_start();
+ ao_sleep(&ao_adc_ring_head);
+ }
+ ao_arch_release_interrupts();
+ return ao_adc_ring_tail();
+}
+
+static inline void
+ao_adc_ack(uint16_t n)
+{
+ ao_arch_block_interrupts();
+ ao_adc_ring_remain -= n;
+ if (!ao_adc_running)
+ _ao_adc_start();
+ ao_arch_release_interrupts();
+}
+