diff --git a/flight/PiOS/STM32F4xx/pios_spi.c b/flight/PiOS/STM32F4xx/pios_spi.c
index de1aa39a9..e030b6826 100644
--- a/flight/PiOS/STM32F4xx/pios_spi.c
+++ b/flight/PiOS/STM32F4xx/pios_spi.c
@@ -247,6 +247,27 @@ int32_t PIOS_SPI_ClaimBus(uint32_t spi_id)
 	return 0;
 }
 
+/**
+ * Claim the SPI bus semaphore from an ISR.  Has no timeout.
+ * \param[in] spi SPI number (0 or 1)
+ * \return 0 if no error
+ * \return -1 if timeout before claiming semaphore
+ */
+int32_t PIOS_SPI_ClaimBusISR(uint32_t spi_id)
+{
+#if defined(PIOS_INCLUDE_FREERTOS)
+	struct pios_spi_dev * spi_dev = (struct pios_spi_dev *)spi_id;
+	
+	bool valid = PIOS_SPI_validate(spi_dev);
+	PIOS_Assert(valid)
+	
+	if (xQueueGenericReceive(( xQueueHandle ) spi_dev->busy, NULL, 0x0000 , pdFALSE ) != pdTRUE)
+		return -1;
+#endif
+	return 0;
+}
+
+
 /**
  * Release the SPI bus semaphore.  Calling the SPI functions does not require this
  * \param[in] spi SPI number (0 or 1)
diff --git a/flight/PiOS/inc/pios_spi.h b/flight/PiOS/inc/pios_spi.h
index d5331848e..8147bd5d9 100644
--- a/flight/PiOS/inc/pios_spi.h
+++ b/flight/PiOS/inc/pios_spi.h
@@ -54,6 +54,7 @@ extern int32_t PIOS_SPI_TransferByte(uint32_t spi_id, uint8_t b);
 extern int32_t PIOS_SPI_TransferBlock(uint32_t spi_id, const uint8_t *send_buffer, uint8_t *receive_buffer, uint16_t len, void *callback);
 extern int32_t PIOS_SPI_Busy(uint32_t spi_id);
 extern int32_t PIOS_SPI_ClaimBus(uint32_t spi_id);
+extern int32_t PIOS_SPI_ClaimBusISR(uint32_t spi_id);
 extern int32_t PIOS_SPI_ReleaseBus(uint32_t spi_id);
 extern void    PIOS_SPI_IRQ_Handler(uint32_t spi_id);
 extern void    PIOS_SPI_SetPrescalar(uint32_t spi_id, uint32_t prescalar);