diff --git a/hw/application_fpga/Makefile b/hw/application_fpga/Makefile
index d45f26f..022dbc5 100644
--- a/hw/application_fpga/Makefile
+++ b/hw/application_fpga/Makefile
@@ -94,7 +94,8 @@ FIRMWARE_OBJS = \
 	$(P)/fw/tk1/lib.o \
 	$(P)/fw/tk1/assert.o \
 	$(P)/fw/tk1/led.o \
-	$(P)/fw/tk1/blake2s/blake2s.o
+	$(P)/fw/tk1/blake2s/blake2s.o \
+	$(P)/fw/tk1/spi.o
 
 FIRMWARE_SOURCES = \
 	$(P)/fw/tk1/main.c \
@@ -102,7 +103,8 @@ FIRMWARE_SOURCES = \
 	$(P)/fw/tk1/lib.c \
 	$(P)/fw/tk1/assert.c \
 	$(P)/fw/tk1/led.c \
-	$(P)/fw/tk1/blake2s/blake2s.c
+	$(P)/fw/tk1/blake2s/blake2s.c \
+	$(P)/fw/tk1/spi.c
 
 TESTFW_OBJS = \
 	$(P)/fw/testfw/main.o \
diff --git a/hw/application_fpga/fw/tk1/main.c b/hw/application_fpga/fw/tk1/main.c
index b6f59ec..3cff710 100644
--- a/hw/application_fpga/fw/tk1/main.c
+++ b/hw/application_fpga/fw/tk1/main.c
@@ -8,6 +8,7 @@
 #include "blake2s/blake2s.h"
 #include "lib.h"
 #include "proto.h"
+#include "spi.h"
 #include "state.h"
 #include "types.h"
 
@@ -30,6 +31,7 @@ static volatile uint32_t *timer_status    = (volatile uint32_t *)TK1_MMIO_TIMER_
 static volatile uint32_t *timer_ctrl      = (volatile uint32_t *)TK1_MMIO_TIMER_CTRL;
 static volatile uint32_t *ram_addr_rand   = (volatile uint32_t *)TK1_MMIO_TK1_RAM_ADDR_RAND;
 static volatile uint32_t *ram_data_rand   = (volatile uint32_t *)TK1_MMIO_TK1_RAM_DATA_RAND;
+static volatile uint32_t *spi_func_addr   = (volatile uint32_t *)TK1_MMIO_TK1_ADDR_SPI_CMD;
 // clang-format on
 
 // Context for the loading of a TKey program
@@ -403,6 +405,7 @@ int main(void)
 
 	// Let the app know the function adddress for blake2s()
 	*fw_blake2s_addr = (uint32_t)blake2s;
+	*spi_func_addr = (uint32_t)spi_ready;
 
 	/*@-mustfreeonly@*/
 	/* Yes, splint, this points directly to RAM and we don't care
diff --git a/hw/application_fpga/fw/tk1/spi.c b/hw/application_fpga/fw/tk1/spi.c
new file mode 100644
index 0000000..3f795ad
--- /dev/null
+++ b/hw/application_fpga/fw/tk1/spi.c
@@ -0,0 +1,102 @@
+// Copyright (C) 2022, 2023 - Tillitis AB
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include "spi.h"
+#include "../tk1_mem.h"
+#include "types.h"
+
+// clang-format off
+static volatile uint32_t *spi_en =         (volatile uint32_t *)(TK1_MMIO_TK1_BASE | 0x200);
+static volatile uint32_t *spi_xfer =       (volatile uint32_t *)(TK1_MMIO_TK1_BASE | 0x204);
+static volatile uint32_t *spi_data =       (volatile uint32_t *)(TK1_MMIO_TK1_BASE | 0x208);
+// clang-format on
+
+// returns non-zero when the SPI-master is ready, and zero if not
+// ready. This can be used to check if the SPI-master is available
+// in the hardware.
+int spi_ready(void)
+{
+	return *spi_xfer;
+}
+
+static void spi_enable(void)
+{
+	*spi_en = 1;
+}
+
+static void spi_disable(void)
+{
+	*spi_en = 0;
+}
+
+static void _spi_write(uint8_t *cmd, size_t size)
+{
+	for (int i = 0; i < size; i++) {
+		while (!spi_ready()) {
+		}
+
+		*spi_data = cmd[i];
+		*spi_xfer = 1;
+	}
+
+	while (!spi_ready()) {
+	}
+}
+
+static void _spi_read(uint8_t *buf, size_t size)
+{
+
+	while (!spi_ready()) {
+	}
+
+	for (int i = 0; i < size; i++) {
+
+		*spi_data = 0x00;
+		*spi_xfer = 1;
+
+		// wait until spi master is done
+		while (!spi_ready()) {
+		}
+
+		buf[i] = (*spi_data & 0xff);
+	}
+}
+
+int spi_write(uint8_t *cmd, size_t cmd_size, uint8_t *data, size_t data_size)
+{
+	if (cmd == NULL || cmd_size == 0) {
+		return -1;
+	}
+
+	spi_enable();
+
+	_spi_write(cmd, cmd_size);
+
+	if (data != NULL && data_size != 0) {
+		_spi_write(data, data_size);
+	}
+
+	spi_disable();
+
+	return 0;
+}
+
+int spi_transfer(uint8_t *tx_buf, size_t tx_size, uint8_t *rx_buf,
+		 size_t rx_size)
+{
+	if (tx_buf == NULL || tx_size == 0) {
+		return -1;
+	}
+
+	spi_enable();
+
+	_spi_write(tx_buf, tx_size);
+
+	if (rx_buf != NULL && rx_size != 0) {
+		_spi_read(rx_buf, rx_size);
+	}
+
+	spi_disable();
+
+	return 0;
+}
diff --git a/hw/application_fpga/fw/tk1/spi.h b/hw/application_fpga/fw/tk1/spi.h
new file mode 100644
index 0000000..e962ce4
--- /dev/null
+++ b/hw/application_fpga/fw/tk1/spi.h
@@ -0,0 +1,14 @@
+// Copyright (C) 2022, 2023 - Tillitis AB
+// SPDX-License-Identifier: GPL-2.0-only
+
+#ifndef TKEY_SPI_H
+#define TKEY_SPI_H
+
+#include "types.h"
+
+int spi_ready(void);
+int spi_write(uint8_t *cmd, size_t size_cmd, uint8_t *data, size_t size_data);
+int spi_transfer(uint8_t *tx_buf, size_t tx_size, uint8_t *rx_buf,
+		 size_t rx_size);
+
+#endif
diff --git a/hw/application_fpga/fw/tk1_mem.h b/hw/application_fpga/fw/tk1_mem.h
index 8bd5c07..b096016 100644
--- a/hw/application_fpga/fw/tk1_mem.h
+++ b/hw/application_fpga/fw/tk1_mem.h
@@ -149,4 +149,9 @@
 #define TK1_MMIO_TK1_SPI_EN 0xff000200
 #define TK1_MMIO_TK1_SPI_XFER 0xff000204
 #define TK1_MMIO_TK1_SPI_DATA 0xff000208
+
+#define TK1_MMIO_TK1_ADDR_SPI_CMD 0xff00020c
+
+
+
 #endif