diff --git a/firmware/common/operacake.c b/firmware/common/operacake.c
index 6230cb39..3a19c4cd 100644
--- a/firmware/common/operacake.c
+++ b/firmware/common/operacake.c
@@ -74,6 +74,9 @@
 
 #define OPERACAKE_MAX_BOARDS 8
 
+#define INVALID_RANGE 0xFF;
+static uint8_t current_range = INVALID_RANGE;
+
 i2c_bus_t* const oc_bus = &i2c0;
 
 enum operacake_switching_mode {
@@ -151,38 +154,6 @@ void operacake_get_boards(uint8_t *addresses) {
 	}
 }
 
-void operacake_set_mode(uint8_t address, uint8_t mode) {
-	if (address >= OPERACAKE_MAX_BOARDS)
-		return;
-
-	operacake_boards[address].mode = mode;
-
-	if (mode == MODE_TIME) {
-		// Switch Opera Cake to pin-control mode
-		uint8_t config_pins = (uint8_t)~(OPERACAKE_PIN_OE(1) | OPERACAKE_PIN_LEDEN(1) | OPERACAKE_PIN_LEDEN2(1));
-		operacake_write_reg(oc_bus, address, OPERACAKE_REG_CONFIG, config_pins);
-		operacake_write_reg(oc_bus, address, OPERACAKE_REG_OUTPUT, OPERACAKE_GPIO_ENABLE | OPERACAKE_EN_LEDS);
-	} else {
-		operacake_write_reg(oc_bus, address, OPERACAKE_REG_CONFIG, OPERACAKE_CONFIG_ALL_OUTPUT);
-		operacake_set_ports(address, operacake_boards[address].PA, operacake_boards[address].PB);
-	}
-
-	// If any boards are in MODE_TIME, enable the sctimer events.
-	bool enable_sctimer = false;
-	for (int i = 0; i < OPERACAKE_MAX_BOARDS; i++) {
-		if (operacake_boards[i].mode == MODE_TIME)
-			enable_sctimer = true;
-	}
-	operacake_sctimer_enable(enable_sctimer);
-}
-
-uint8_t operacake_get_mode(uint8_t address) {
-	if (address >= OPERACAKE_MAX_BOARDS)
-		return 0;
-
-	return operacake_boards[address].mode;
-}
-
 uint8_t port_to_pins(uint8_t port) {
 	switch(port) {
 		case OPERACAKE_PA1:
@@ -206,46 +177,98 @@ uint8_t port_to_pins(uint8_t port) {
 	return 0xFF;
 }
 
-uint8_t operacake_set_ports(uint8_t address, uint8_t PA, uint8_t PB) {
+/*
+ * Issue I2C command to activate ports.
+ */
+uint8_t operacake_activate_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)) {
+	/* Ensure PA and PB are within the valid range. */
+	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))) {
+	/* Ensure PA and PB are on opposite sides. */
+	if (((PA <= OPERACAKE_PA4) && (PB <= OPERACAKE_PA4))
+			|| ((PA > OPERACAKE_PA4) && (PB > OPERACAKE_PA4))) {
 		return 1;
 	}
 
-	if(PA > OPERACAKE_PA4) {
+	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;
+}
+
+void operacake_set_mode(uint8_t address, uint8_t mode) {
+	if (address >= OPERACAKE_MAX_BOARDS)
+		return;
+
+	operacake_boards[address].mode = mode;
+	current_range = INVALID_RANGE;
+
+	if (mode == MODE_TIME) {
+		// Switch Opera Cake to pin-control mode
+		uint8_t config_pins = (uint8_t)~(OPERACAKE_PIN_OE(1) | OPERACAKE_PIN_LEDEN(1) | OPERACAKE_PIN_LEDEN2(1));
+		operacake_write_reg(oc_bus, address, OPERACAKE_REG_CONFIG, config_pins);
+		operacake_write_reg(oc_bus, address, OPERACAKE_REG_OUTPUT, OPERACAKE_GPIO_ENABLE | OPERACAKE_EN_LEDS);
+	} else {
+		operacake_write_reg(oc_bus, address, OPERACAKE_REG_CONFIG, OPERACAKE_CONFIG_ALL_OUTPUT);
+		operacake_activate_ports(address, operacake_boards[address].PA, operacake_boards[address].PB);
+	}
+
+	// If any boards are in MODE_TIME, enable the sctimer events.
+	bool enable_sctimer = false;
+	for (int i = 0; i < OPERACAKE_MAX_BOARDS; i++) {
+		if (operacake_boards[i].mode == MODE_TIME)
+			enable_sctimer = true;
+	}
+	operacake_sctimer_enable(enable_sctimer);
+}
+
+uint8_t operacake_get_mode(uint8_t address) {
+	if (address >= OPERACAKE_MAX_BOARDS)
+		return 0;
+
+	return operacake_boards[address].mode;
+}
+
+/*
+ * Set manual mode ports.
+ */
+uint8_t operacake_set_ports(uint8_t address, uint8_t PA, uint8_t PB)
+{
+	/* Ensure PA and PB are within the valid range. */
+	if ((PA > OPERACAKE_PB4) || (PB > OPERACAKE_PB4)) {
+		return 1;
+	}
+	/* Ensure PA and PB are on opposite sides. */
+	if (((PA <= OPERACAKE_PA4) && (PB <= OPERACAKE_PA4))
+			|| ((PA > OPERACAKE_PA4) && (PB > OPERACAKE_PA4))) {
+		return 1;
+	}
+
 	// Keep track of manual settings for when we switch in/out of time/frequency modes.
 	operacake_boards[address].PA = PA;
 	operacake_boards[address].PB = PB;
 
-	// Only apply register settings if the board is in manual mode.
-	if (operacake_boards[address].mode != MODE_MANUAL)
-		return 0;
+	// Immediately apply register settings if the board is in manual mode.
+	if (operacake_boards[address].mode == MODE_MANUAL) {
+		return operacake_activate_ports(address, PA, PB);
+	}
 
-	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;
 }
 
 /*
- * Opera Glasses
+ * frequency mode aka "Opera Glasses"
  */
 typedef struct {
 	uint16_t freq_min;
@@ -264,18 +287,19 @@ uint8_t operacake_add_range(uint16_t freq_min, uint16_t freq_max, uint8_t port)
 	ranges[range_idx].freq_min = freq_min;
 	ranges[range_idx].freq_max = freq_max;
 	ranges[range_idx].portA = port;
-	ranges[range_idx].portB = 7;
-	if(port <= OPERACAKE_PA4) {
-		ranges[range_idx].portB = range_idx+4;
-	} else {
-		ranges[range_idx].portB = OPERACAKE_PA1;
-	}
+	/* Make the B port mirror the A port. */
+	ranges[range_idx].portB = (port + 4) % 8;
 	range_idx++;
+	current_range = INVALID_RANGE;
 	return 0;
 }
 
+void operacake_clear_ranges(void)
+{
+        range_idx = 0;
+}
+
 #define FREQ_ONE_MHZ (1000000ull)
-static uint8_t current_range = 0xFF;
 
 uint8_t operacake_set_range(uint32_t freq_mhz) {
 	if(range_idx == 0) {
@@ -289,13 +313,17 @@ uint8_t operacake_set_range(uint32_t freq_mhz) {
 			break;
 		}
 	}
+	/* Use the last range if there was no match. */
+	if (range == range_idx) {
+		range--;
+	}
 	if(range == current_range) {
 		return 1;
 	}
 
 	for (int i = 0; i < OPERACAKE_MAX_BOARDS; i++) {
 		if (operacake_is_board_present(i) && operacake_get_mode(i) == MODE_FREQUENCY) {
-			operacake_set_ports(i, ranges[range].portA, ranges[range].portB);
+			operacake_activate_ports(i, ranges[range].portA, ranges[range].portB);
 			break;
 		}
 	}
diff --git a/firmware/common/operacake.h b/firmware/common/operacake.h
index 88bb135c..3b2621bb 100644
--- a/firmware/common/operacake.h
+++ b/firmware/common/operacake.h
@@ -50,6 +50,7 @@ uint8_t operacake_get_mode(uint8_t address);
 uint8_t operacake_set_ports(uint8_t address, uint8_t PA, uint8_t PB);
 uint8_t operacake_add_range(uint16_t freq_min, uint16_t freq_max, uint8_t port);
 uint8_t operacake_set_range(uint32_t freq_mhz);
+void operacake_clear_ranges(void);
 uint16_t gpio_test(uint8_t address);
 
 #ifdef __cplusplus
diff --git a/firmware/hackrf_usb/usb_api_operacake.c b/firmware/hackrf_usb/usb_api_operacake.c
index 00374522..43f14a52 100644
--- a/firmware/hackrf_usb/usb_api_operacake.c
+++ b/firmware/hackrf_usb/usb_api_operacake.c
@@ -65,6 +65,7 @@ usb_request_status_t usb_vendor_request_operacake_set_ranges(
 		if((num_ranges == 0) || (num_ranges > MAX_OPERACAKE_RANGES)) {
 			return USB_REQUEST_STATUS_STALL;
 		}
+		operacake_clear_ranges();
 		usb_transfer_schedule_block(endpoint->out, &data,
 				endpoint->setup.length, NULL, NULL);
 	} else if (stage == USB_TRANSFER_STAGE_DATA) {
diff --git a/host/hackrf-tools/src/hackrf_operacake.c b/host/hackrf-tools/src/hackrf_operacake.c
index d2db60bc..763a673a 100644
--- a/host/hackrf-tools/src/hackrf_operacake.c
+++ b/host/hackrf-tools/src/hackrf_operacake.c
@@ -57,9 +57,9 @@ static void usage() {
 }
 
 static struct option long_options[] = {
-	{ "device", no_argument, 0, 'd' },
-	{ "address", no_argument, 0, 'o' },
-	{ "mode", no_argument, 0, 'm' },
+	{ "device", required_argument, 0, 'd' },
+	{ "address", required_argument, 0, 'o' },
+	{ "mode", required_argument, 0, 'm' },
 	{ "list", no_argument, 0, 'l' },
 	{ "gpio_test", no_argument, 0, 'g' },
 	{ "help", no_argument, 0, 'h' },
diff --git a/host/libhackrf/src/hackrf.c b/host/libhackrf/src/hackrf.c
index 5be23d6f..025c2d59 100644
--- a/host/libhackrf/src/hackrf.c
+++ b/host/libhackrf/src/hackrf.c
@@ -2204,7 +2204,7 @@ int ADDCALL hackrf_get_operacake_mode(hackrf_device* device, uint8_t address, en
 	}
 }
 
-/* Set Operacake ports */
+/* Set Operacake manual mode ports. */
 int ADDCALL hackrf_set_operacake_ports(hackrf_device* device,
                                        uint8_t address,
                                        uint8_t port_a,
diff --git a/host/libhackrf/src/hackrf.h b/host/libhackrf/src/hackrf.h
index 70acec8c..4fb56363 100644
--- a/host/libhackrf/src/hackrf.h
+++ b/host/libhackrf/src/hackrf.h
@@ -110,7 +110,7 @@ enum operacake_switching_mode {
 	 */
 	OPERACAKE_MODE_MANUAL,
 	/**
-	 * Port connections are switched automatically when the frequency is changed. Frequency ranges can be set using @ref hackrf_set_operacake_ranges.
+	 * Port connections are switched automatically when the frequency is changed. Frequency ranges can be set using @ref hackrf_set_operacake_freq_ranges.
 	 */
 	OPERACAKE_MODE_FREQUENCY,
 	/**