diff --git a/firmware/common/hackrf_core.h b/firmware/common/hackrf_core.h
index a1b9b00f..974fa5ee 100644
--- a/firmware/common/hackrf_core.h
+++ b/firmware/common/hackrf_core.h
@@ -240,6 +240,7 @@ extern w25q80bv_driver_t spi_flash;
 extern sgpio_config_t sgpio_config;
 extern rf_path_t rf_path;
 extern jtag_t jtag_cpld;
+extern i2c_bus_t i2c0;
 
 void cpu_clock_init(void);
 void cpu_clock_pll1_low_speed(void);
diff --git a/firmware/common/i2c_lpc.c b/firmware/common/i2c_lpc.c
index f7bf4393..607a1a0a 100644
--- a/firmware/common/i2c_lpc.c
+++ b/firmware/common/i2c_lpc.c
@@ -44,17 +44,23 @@ void i2c_lpc_transfer(i2c_bus_t* const bus,
 	uint8_t* const data_rx, const size_t count_rx
 ) {
 	const uint32_t port = (uint32_t)bus->obj;
-	i2c_tx_start(port);
-	i2c_tx_byte(port, (slave_address << 1) | I2C_WRITE);
-	for(size_t i=0; i<count_tx; i++) {
-		i2c_tx_byte(port, data_tx[i]);
+	size_t i;
+	bool ack = false;
+	if (data_tx && (count_tx > 0)) {
+		i2c_tx_start(port);
+		i2c_tx_byte(port, (slave_address << 1) | I2C_WRITE);
+		for(i=0; i<count_tx; i++) {
+			i2c_tx_byte(port, data_tx[i]);
+		}
 	}
 
-	if( data_rx ) {
+	if (data_rx && (count_rx > 0)) {
 		i2c_tx_start(port);
 		i2c_tx_byte(port, (slave_address << 1) | I2C_READ);
-		for(size_t i=0; i<count_rx; i++) {
-			data_rx[i] = i2c_rx_byte(port);
+		for(i=0; i<count_rx; i++) {
+			/* ACK each byte except the last */
+			ack = (i!=count_rx-1);
+			data_rx[i] = i2c_rx_byte(port, ack);
 		}
 	}
 
diff --git a/firmware/common/operacake.c b/firmware/common/operacake.c
new file mode 100644
index 00000000..ec7df4ba
--- /dev/null
+++ b/firmware/common/operacake.c
@@ -0,0 +1,146 @@
+/*
+ * Copyright 2016 Dominic Spill <dominicgs@gmail.com>
+ *
+ * This file is part of HackRF.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#include "operacake.h"
+#include "hackrf_core.h"
+
+#define OPERACAKE_PIN_OE(x)      (x<<7)
+#define OPERACAKE_PIN_U2CTRL1(x) (x<<6)
+#define OPERACAKE_PIN_U2CTRL0(x) (x<<5)
+#define OPERACAKE_PIN_U3CTRL1(x) (x<<4)
+#define OPERACAKE_PIN_U3CTRL0(x) (x<<3)
+#define OPERACAKE_PIN_U1CTRL(x)  (x<<2)
+#define OPERACAKE_PIN_LEDEN2(x)  (x<<1)
+#define OPERACAKE_PIN_LEDEN(x)   (x<<0)
+
+#define OPERACAKE_PORT_A1 (OPERACAKE_PIN_U2CTRL0(0) | OPERACAKE_PIN_U2CTRL1(0))
+#define OPERACAKE_PORT_A2 (OPERACAKE_PIN_U2CTRL0(1) | OPERACAKE_PIN_U2CTRL1(0))
+#define OPERACAKE_PORT_A3 (OPERACAKE_PIN_U2CTRL0(0) | OPERACAKE_PIN_U2CTRL1(1))
+#define OPERACAKE_PORT_A4 (OPERACAKE_PIN_U2CTRL0(1) | OPERACAKE_PIN_U2CTRL1(1))
+
+#define OPERACAKE_PORT_B1 (OPERACAKE_PIN_U3CTRL0(0) | OPERACAKE_PIN_U3CTRL1(0))
+#define OPERACAKE_PORT_B2 (OPERACAKE_PIN_U3CTRL0(1) | OPERACAKE_PIN_U3CTRL1(0))
+#define OPERACAKE_PORT_B3 (OPERACAKE_PIN_U3CTRL0(0) | OPERACAKE_PIN_U3CTRL1(1))
+#define OPERACAKE_PORT_B4 (OPERACAKE_PIN_U3CTRL0(1) | OPERACAKE_PIN_U3CTRL1(1))
+
+#define OPERACAKE_SAMESIDE  OPERACAKE_PIN_U1CTRL(1)
+#define OPERACAKE_CROSSOVER OPERACAKE_PIN_U1CTRL(0)
+#define OPERACAKE_EN_LEDS (OPERACAKE_PIN_LEDEN2(1) | OPERACAKE_PIN_LEDEN2(0))
+#define OPERACAKE_GPIO_EN OPERACAKE_PIN_OE(0)
+#define OPERACAKE_GPIO_DISABLE OPERACAKE_PIN_OE(1)
+
+#define OPERACAKE_REG_INPUT    0x00
+#define OPERACAKE_REG_OUTPUT   0x01
+#define OPERACAKE_REG_POLARITY 0x02
+#define OPERACAKE_REG_CONFIG   0x03
+
+#define OPERACAKE_DEFAULT_OUTPUT (OPERACAKE_GPIO_DISABLE | OPERACAKE_SAMESIDE \
+								  | OPERACAKE_PORT_A1 | OPERACAKE_PORT_B1 \
+								  | OPERACAKE_EN_LEDS)
+#define OPERACAKE_CONFIG_ALL_OUTPUT (0x00)
+
+#define OPERACAKE_DEFAULT_ADDRESS 0x18
+
+i2c_bus_t* const oc_bus = &i2c0;
+uint8_t operacake_boards[8] = {0,0,0,0,0,0,0,0};
+
+/* read single register */
+uint8_t operacake_read_reg(i2c_bus_t* const bus, uint8_t address, uint8_t reg) {
+	const uint8_t data_tx[] = { reg };
+	uint8_t data_rx[] = { 0x00 };
+	i2c_bus_transfer(bus, address, data_tx, 1, data_rx, 1);
+	return data_rx[0];
+}
+
+/* Write to one of the PCA9557 registers */
+void operacake_write_reg(i2c_bus_t* const bus, uint8_t address, uint8_t reg, uint8_t value) {
+	const uint8_t data[] = {reg, value};
+	i2c_bus_transfer(bus, address, data, 2, NULL, 0);
+}
+
+uint8_t operacake_init(void) {
+	uint8_t reg, addr, i, j = 0;
+	/* Find connected operacakes */
+	for(i=0; i<8; i++) {
+		addr = OPERACAKE_DEFAULT_ADDRESS | i;
+		operacake_write_reg(oc_bus, addr, OPERACAKE_REG_OUTPUT,
+		                    OPERACAKE_DEFAULT_OUTPUT);
+		operacake_write_reg(oc_bus, addr, OPERACAKE_REG_CONFIG,
+		                    OPERACAKE_CONFIG_ALL_OUTPUT);
+		reg = operacake_read_reg(oc_bus, addr, OPERACAKE_REG_CONFIG);
+		if(reg==OPERACAKE_CONFIG_ALL_OUTPUT)
+			operacake_boards[j++] = addr;
+	}
+	return 0;
+}
+
+uint8_t port_to_pins(uint8_t port) {
+	switch(port) {
+		case OPERACAKE_PA1:
+			return OPERACAKE_PORT_A1;
+		case OPERACAKE_PA2:
+			return OPERACAKE_PORT_A2;
+		case OPERACAKE_PA3:
+			return OPERACAKE_PORT_A3;
+		case OPERACAKE_PA4:
+			return OPERACAKE_PORT_A4;
+
+		case OPERACAKE_PB1:
+			return OPERACAKE_PORT_B1;
+		case OPERACAKE_PB2:
+			return OPERACAKE_PORT_B2;
+		case OPERACAKE_PB3:
+			return OPERACAKE_PORT_B3;
+		case OPERACAKE_PB4:
+			return OPERACAKE_PORT_B4;
+	}
+	return 0xFF;
+}
+
+uint8_t operacake_set_ports(uint8_t address, uint8_t PA, uint8_t PB) {
+	uint8_t side, pa, pb, reg;
+	/* Start with some error checking,
+	 * which should have been done either
+	 * on the host or elsewhere in firmware
+	 */
+	if((PA > OPERACAKE_PB4) || (PB > OPERACAKE_PB4)) {
+		return 1;
+	}
+	/* Check which side PA and PB are on */
+	if(((PA <= OPERACAKE_PA4) && (PB <= OPERACAKE_PA4))
+	    || ((PA > OPERACAKE_PA4) && (PB > OPERACAKE_PA4))) {
+		return 1;
+	}
+	
+	if(PA > OPERACAKE_PA4)
+		side = OPERACAKE_CROSSOVER;
+	else
+		side = OPERACAKE_SAMESIDE;
+
+		pa = port_to_pins(PA);
+		pb = port_to_pins(PB);
+		
+	reg = (OPERACAKE_GPIO_DISABLE | side
+					| pa | pb | OPERACAKE_EN_LEDS);
+	operacake_write_reg(oc_bus, address, OPERACAKE_REG_OUTPUT, reg);
+	return 0;
+}
+
diff --git a/firmware/common/operacake.h b/firmware/common/operacake.h
new file mode 100644
index 00000000..0fda1f2b
--- /dev/null
+++ b/firmware/common/operacake.h
@@ -0,0 +1,53 @@
+/*
+ * Copyright 2016 Dominic Spill <dominicgs@gmail.com>
+ *
+ * This file is part of HackRF.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifndef __OPERACAKE_H
+#define __OPERACAKE_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+#include <stdint.h>
+#include "i2c_bus.h"
+
+#define OPERACAKE_PA1 0
+#define OPERACAKE_PA2 1
+#define OPERACAKE_PA3 2
+#define OPERACAKE_PA4 3
+
+#define OPERACAKE_PB1 4
+#define OPERACAKE_PB2 5
+#define OPERACAKE_PB3 6
+#define OPERACAKE_PB4 7
+
+/* Up to 8 Operacake boards can be used with one HackRF */
+extern uint8_t operacake_boards[8];
+
+uint8_t operacake_init(void);
+uint8_t operacake_set_ports(uint8_t address, uint8_t PA, uint8_t PB);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __OPERACAKE_H */
diff --git a/firmware/hackrf_usb/CMakeLists.txt b/firmware/hackrf_usb/CMakeLists.txt
index c9c9a9d4..29272b79 100644
--- a/firmware/hackrf_usb/CMakeLists.txt
+++ b/firmware/hackrf_usb/CMakeLists.txt
@@ -42,6 +42,8 @@ set(SRC_M4
 	usb_api_register.c
 	usb_api_spiflash.c
 	usb_api_transceiver.c
+	"${PATH_HACKRF_FIRMWARE_COMMON}/operacake.c"
+	usb_api_operacake.c
 	usb_api_sweep.c
 	"${PATH_HACKRF_FIRMWARE_COMMON}/usb_queue.c"
 	"${PATH_HACKRF_FIRMWARE_COMMON}/fault_handler.c"
diff --git a/firmware/hackrf_usb/hackrf_usb.c b/firmware/hackrf_usb/hackrf_usb.c
index ba31908a..046934c7 100644
--- a/firmware/hackrf_usb/hackrf_usb.c
+++ b/firmware/hackrf_usb/hackrf_usb.c
@@ -40,6 +40,8 @@
 #include "usb_api_cpld.h"
 #include "usb_api_register.h"
 #include "usb_api_spiflash.h"
+#include "usb_api_operacake.h"
+#include "operacake.h"
 #include "usb_api_sweep.h"
 
 #include "usb_api_transceiver.h"
@@ -77,6 +79,8 @@ static const usb_request_handler_fn vendor_request_handler[] = {
 	usb_vendor_request_set_freq_explicit,
 	usb_vendor_request_read_wcid,  // USB_WCID_VENDOR_REQ
 	usb_vendor_request_init_sweep,
+	usb_vendor_request_operacake_get_boards,
+	usb_vendor_request_operacake_set_ports
 };
 
 static const uint32_t vendor_request_handler_count =
@@ -174,6 +178,7 @@ int main(void) {
 	usb_run(&usb_device);
 	
 	rf_path_init(&rf_path);
+	operacake_init();
 
 	unsigned int phase = 0;
 
diff --git a/firmware/hackrf_usb/usb_api_operacake.c b/firmware/hackrf_usb/usb_api_operacake.c
new file mode 100644
index 00000000..d9e5affa
--- /dev/null
+++ b/firmware/hackrf_usb/usb_api_operacake.c
@@ -0,0 +1,49 @@
+/*
+ * Copyright 2016 Dominic Spill <dominicgs@gmail.com>
+ *
+ * This file is part of HackRF.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#include "usb_api_operacake.h"
+#include "usb_queue.h"
+
+#include <operacake.h>
+
+usb_request_status_t usb_vendor_request_operacake_get_boards(
+	usb_endpoint_t* const endpoint, const usb_transfer_stage_t stage)
+{
+	if (stage == USB_TRANSFER_STAGE_SETUP) {
+		usb_transfer_schedule_block(endpoint->in, operacake_boards, 8, NULL, NULL);
+		usb_transfer_schedule_ack(endpoint->out);
+	}
+	return USB_REQUEST_STATUS_OK;
+}
+
+usb_request_status_t usb_vendor_request_operacake_set_ports(
+	usb_endpoint_t* const endpoint, const usb_transfer_stage_t stage)
+{
+	uint8_t address, port_a, port_b;
+	address = endpoint->setup.value & 0xFF;
+	port_a = endpoint->setup.index & 0xFF;
+	port_b = (endpoint->setup.index >> 8) & 0xFF;
+	if (stage == USB_TRANSFER_STAGE_SETUP) {
+		operacake_set_ports(address, port_a, port_b);
+		usb_transfer_schedule_ack(endpoint->in);
+	}
+	return USB_REQUEST_STATUS_OK;
+}
diff --git a/firmware/hackrf_usb/usb_api_operacake.h b/firmware/hackrf_usb/usb_api_operacake.h
new file mode 100644
index 00000000..4339488d
--- /dev/null
+++ b/firmware/hackrf_usb/usb_api_operacake.h
@@ -0,0 +1,34 @@
+/*
+ * Copyright 2016 Dominic Spill <dominicgs@gmail.com>
+ *
+ * This file is part of HackRF.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifndef __USB_API_OPERACAKE_H__
+#define __USB_API_OPERACAKE_H__
+
+#include <usb_type.h>
+#include <usb_request.h>
+
+usb_request_status_t  usb_vendor_request_operacake_get_boards(
+	usb_endpoint_t* const endpoint, const usb_transfer_stage_t stage);
+
+usb_request_status_t usb_vendor_request_operacake_set_ports(
+	usb_endpoint_t* const endpoint, const usb_transfer_stage_t stage);
+
+#endif /* end of include guard: __USB_API_OPERACAKE_H__ */
diff --git a/firmware/libopencm3 b/firmware/libopencm3
index 50c51c7b..0ca89139 160000
--- a/firmware/libopencm3
+++ b/firmware/libopencm3
@@ -1 +1 @@
-Subproject commit 50c51c7b5fd2f113440241bb13be3a0e64724b8d
+Subproject commit 0ca89139446586e743b842fb1074db0f2173f6dd
diff --git a/host/hackrf-tools/src/CMakeLists.txt b/host/hackrf-tools/src/CMakeLists.txt
index e4e2389a..b30e492c 100644
--- a/host/hackrf-tools/src/CMakeLists.txt
+++ b/host/hackrf-tools/src/CMakeLists.txt
@@ -40,6 +40,7 @@ SET(TOOLS
 	hackrf_spiflash
 	hackrf_cpldjtag
 	hackrf_info
+	hackrf_operacake
 	hackrf_sweep
 )
 
diff --git a/host/hackrf-tools/src/hackrf_info.c b/host/hackrf-tools/src/hackrf_info.c
index eed24c37..def5371d 100644
--- a/host/hackrf-tools/src/hackrf_info.c
+++ b/host/hackrf-tools/src/hackrf_info.c
@@ -32,9 +32,10 @@ int main(void)
 	uint8_t board_id = BOARD_ID_INVALID;
 	char version[255 + 1];
 	read_partid_serialno_t read_partid_serialno;
+	uint8_t operacakes[8];
 	hackrf_device_list_t *list;
 	hackrf_device* device;
-	int i;
+	int i, j;
 
 	result = hackrf_init();
 	if (result != HACKRF_SUCCESS) {
@@ -98,7 +99,20 @@ int main(void)
 					read_partid_serialno.serial_no[1],
 					read_partid_serialno.serial_no[2],
 					read_partid_serialno.serial_no[3]);
-		
+
+		result = hackrf_get_operacake_boards(device, &operacakes[0]);
+		if (result != HACKRF_SUCCESS) {
+			fprintf(stderr, "hackrf_get_operacake_boards() failed: %s (%d)\n",
+					hackrf_error_name(result), result);
+			return EXIT_FAILURE;
+		}
+		for(j=0; j<8; j++) {
+			if(operacakes[j] == 0)
+				break;
+			printf("Operacake found, address: 0x%02x\n", operacakes[j]);
+
+		}
+
 		result = hackrf_close(device);
 		if (result != HACKRF_SUCCESS) {
 			fprintf(stderr, "hackrf_close() failed: %s (%d)\n",
diff --git a/host/hackrf-tools/src/hackrf_operacake.c b/host/hackrf-tools/src/hackrf_operacake.c
new file mode 100644
index 00000000..086af5cb
--- /dev/null
+++ b/host/hackrf-tools/src/hackrf_operacake.c
@@ -0,0 +1,158 @@
+/*
+ * Copyright 2016 Dominic Spill <dominicgs@gmail.com>
+ *
+ * This file is part of HackRF.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#include <hackrf.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <getopt.h>
+
+#ifndef bool
+typedef int bool;
+#define true 1
+#define false 0
+#endif
+
+static void usage() {
+	printf("\nUsage:\n");
+	printf("\t-s, --serial <s>: specify a particular device by serial number\n");
+	printf("\t-d, --device <n>: specify a particular device by number\n");
+	printf("\t-o, --address <n>: specify a particular operacake by address [default: 0x00]\n");
+	printf("\t-a <n>: set port A connection\n");
+	printf("\t-b <n>: set port B connection\n");
+	printf("\t-v: verbose, list available operacake boards\n");
+}
+
+static struct option long_options[] = {
+	{ "device", no_argument, 0, 'd' },
+	{ "serial", no_argument, 0, 's' },
+	{ "address", no_argument, 0, 'o' },
+	{ 0, 0, 0, 0 },
+};
+
+int parse_int(char* const s, uint16_t* const value) {
+	char* s_end = s;
+	const long long_value = strtol(s, &s_end, 10);
+	if( (s != s_end) && (*s_end == 0) ) {
+		*value = (uint16_t)long_value;
+		return HACKRF_SUCCESS;
+	} else {
+		return HACKRF_ERROR_INVALID_PARAM;
+	}
+}
+
+int main(int argc, char** argv) {
+	int opt;
+	const char* serial_number = NULL;
+	int device_index = 0;
+	int operacake_address = 0;
+	int port_a = 0;
+	int port_b = 0;
+	int verbose = 0;
+	uint8_t operacakes[8];
+	int i = 0;
+	hackrf_device* device = NULL;
+	int option_index = 0;
+
+	int result = hackrf_init();
+	if( result ) {
+		printf("hackrf_init() failed: %s (%d)\n", hackrf_error_name(result), result);
+		return -1;
+	}
+
+	while( (opt = getopt_long(argc, argv, "d:s:o:a:b:v", long_options, &option_index)) != EOF ) {
+		switch( opt ) {
+		case 'd':
+			device_index = atoi(optarg);
+			break;
+
+		case 's':
+			serial_number = optarg;
+			break;
+
+		case 'o':
+			operacake_address = atoi(optarg);
+			break;
+
+		case 'a':
+			port_a = atoi(optarg);
+			break;
+
+		case 'b':
+			port_b = atoi(optarg);
+			break;
+
+		case 'v':
+			verbose = 1;
+			break;
+
+		default:
+			usage();
+		}
+		
+		if( result != HACKRF_SUCCESS ) {
+			printf("argument error: %s (%d)\n", hackrf_error_name(result), result);
+			break;
+		}
+	}
+
+	if(serial_number != NULL) {
+		result = hackrf_open_by_serial(serial_number, &device);
+	} else {
+		hackrf_device_list_t* device_list = hackrf_device_list();
+		if(device_list->devicecount <= 0) {
+			result = HACKRF_ERROR_NOT_FOUND;
+		} else {
+			result = hackrf_device_list_open(device_list, device_index, &device);
+		}	
+	}
+
+	if( result ) {
+		printf("hackrf_open() failed: %s (%d)\n", hackrf_error_name(result), result);
+		return -1;
+	}
+
+	if(verbose) {
+		hackrf_get_operacake_boards(device, operacakes);
+		printf("Operacakes found:\n");
+		for(i=0; i<8; i++) {
+			if(operacakes[i] !=0)
+				printf("%d\n", operacakes[i]);
+		}
+		printf("\n");
+	}
+
+	result = hackrf_set_operacake_ports(device, operacake_address, port_a, port_b);
+	if( result ) {
+		printf("hackrf_set_operacake_ports() failed: %s (%d)\n", hackrf_error_name(result), result);
+		return -1;
+	}
+
+	result = hackrf_close(device);
+	if( result ) {
+		printf("hackrf_close() failed: %s (%d)\n", hackrf_error_name(result), result);
+		return -1;
+	}
+	
+	hackrf_exit();
+	
+	return 0;
+}
diff --git a/host/libhackrf/src/hackrf.c b/host/libhackrf/src/hackrf.c
index ec995538..3b57a5a6 100644
--- a/host/libhackrf/src/hackrf.c
+++ b/host/libhackrf/src/hackrf.c
@@ -69,6 +69,8 @@ typedef enum {
 	HACKRF_VENDOR_REQUEST_SET_FREQ_EXPLICIT = 24,
 	// USB_WCID_VENDOR_REQ = 25
 	HACKRF_VENDOR_REQUEST_INIT_SWEEP = 26,
+	HACKRF_VENDOR_REQUEST_OPERACAKE_GET_BOARDS = 27,
+	HACKRF_VENDOR_REQUEST_OPERACAKE_SET_PORTS = 28,
 } hackrf_vendor_request;
 
 typedef enum {
@@ -1698,6 +1700,7 @@ uint32_t ADDCALL hackrf_compute_baseband_filter_bw(const uint32_t bandwidth_hz)
 	return p->bandwidth_hz;
 }
 
+/* Initialise sweep mode with alist of frequencies and dwell time in samples */
 int ADDCALL hackrf_init_sweep(hackrf_device* device, uint16_t* frequency_list, int length, uint32_t dwell_time)
 {
 	int result, i;
@@ -1724,6 +1727,65 @@ int ADDCALL hackrf_init_sweep(hackrf_device* device, uint16_t* frequency_list, i
 	}
 }
 
+/* Retrieve list of Operacake board addresses 
+ * boards must be *uint8_t[8]
+ */
+int ADDCALL hackrf_get_operacake_boards(hackrf_device* device, uint8_t* boards)
+{
+	int result;
+	result = libusb_control_transfer(
+		device->usb_device,
+		LIBUSB_ENDPOINT_IN | LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_RECIPIENT_DEVICE,
+		HACKRF_VENDOR_REQUEST_OPERACAKE_GET_BOARDS,
+		0,
+		0,
+		boards,
+		8,
+		0
+	);
+
+	if (result < 8)
+	{
+		return HACKRF_ERROR_LIBUSB;
+	} else {
+		return HACKRF_SUCCESS;
+	}
+}
+
+/* Set Operacake ports */
+int ADDCALL hackrf_set_operacake_ports(hackrf_device* device,
+                                       uint8_t address,
+                                       uint8_t port_a,
+                                       uint8_t port_b)
+{
+	int result;
+	/* Error checking */
+	if((port_a > OPERACAKE_PB4) || (port_b > OPERACAKE_PB4)) {
+		return HACKRF_ERROR_INVALID_PARAM;
+	}
+	/* Check which side PA and PB are on */
+	if(((port_a <= OPERACAKE_PA4) && (port_b <= OPERACAKE_PA4))
+	    || ((port_a > OPERACAKE_PA4) && (port_b > OPERACAKE_PA4))) {
+		return HACKRF_ERROR_INVALID_PARAM;
+	}
+	result = libusb_control_transfer(
+		device->usb_device,
+		LIBUSB_ENDPOINT_OUT | LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_RECIPIENT_DEVICE,
+		HACKRF_VENDOR_REQUEST_OPERACAKE_SET_PORTS,
+		address,
+		port_a | (port_b<<8),
+		NULL,
+		0,
+		0
+	);
+
+	if (result != 0) {
+		return HACKRF_ERROR_LIBUSB;
+	} else {
+		return HACKRF_SUCCESS;
+	}
+}
+
 #ifdef __cplusplus
 } // __cplusplus defined.
 #endif
diff --git a/host/libhackrf/src/hackrf.h b/host/libhackrf/src/hackrf.h
index a318f6ed..584dd292 100644
--- a/host/libhackrf/src/hackrf.h
+++ b/host/libhackrf/src/hackrf.h
@@ -83,6 +83,17 @@ enum rf_path_filter {
 	RF_PATH_FILTER_HIGH_PASS = 2,
 };
 
+enum operacake_ports {
+	OPERACAKE_PA1 = 0,
+	OPERACAKE_PA2 = 1,
+	OPERACAKE_PA3 = 2,
+	OPERACAKE_PA4 = 3,
+	OPERACAKE_PB1 = 4,
+	OPERACAKE_PB2 = 5,
+	OPERACAKE_PB3 = 6,
+	OPERACAKE_PB4 = 7,
+};
+
 typedef struct hackrf_device hackrf_device;
 
 typedef struct {
@@ -201,6 +212,13 @@ extern ADDAPI int ADDCALL hackrf_init_sweep(hackrf_device* device,
 											uint16_t* frequency_list,
 											int length, uint32_t dwell_time);
 
+/* Operacake functions */
+int ADDCALL hackrf_get_operacake_boards(hackrf_device* device, uint8_t* boards);
+int ADDCALL hackrf_set_operacake_ports(hackrf_device* device,
+                                       uint8_t address,
+                                       uint8_t port_a,
+                                       uint8_t port_b);
+
 #ifdef __cplusplus
 } // __cplusplus defined.
 #endif