Add USB control of LPF baseband filter.

Add max2837_set_lpf_bandwidth() function to choose available LPF filter bandwidth based on bandwidth in Hz.
Change configuration of MAX2837 to set LPF_EN and FT at max2837_setup(), not in max2837_rx() or max2837_tx() (which was overriding prior filter configuration).

firmware/common/hackrf_core.c

@@ -22,6 +22,7 @@
 
 #include "hackrf_core.h"
 #include "si5351c.h"
+#include "max2837.h"
 #include <libopencm3/lpc43xx/i2c.h>
 #include <libopencm3/lpc43xx/cgu.h>
 #include <libopencm3/lpc43xx/gpio.h>
@@ -126,6 +127,10 @@ bool sample_rate_set(const uint32_t sample_rate_hz) {
 #endif
 }
 
+bool baseband_filter_bandwidth_set(const uint32_t bandwidth_hz) {
+	return max2837_set_lpf_bandwidth(bandwidth_hz);
+}
+
 /* clock startup for Jellybean with Lemondrop attached */ 
 void cpu_clock_init(void)
 {

firmware/common/hackrf_core.h

@@ -218,6 +218,7 @@ void pin_setup(void);
 void enable_1v8_power(void);
 
 bool sample_rate_set(const uint32_t sampling_rate_hz);
+bool baseband_filter_bandwidth_set(const uint32_t bandwidth_hz);
 
 #ifdef __cplusplus
 }

firmware/common/max2837.c

@@ -115,6 +115,11 @@ void max2837_setup(void)
 	/* maximum rx output common-mode voltage */
 	set_MAX2837_BUFF_VCM(MAX2837_BUFF_VCM_1_25);
 
+	/* configure baseband filter for 8 MHz TX */
+	set_MAX2837_LPF_EN(1);
+	set_MAX2837_ModeCtrl(MAX2837_ModeCtrl_RxLPF);
+	set_MAX2837_FT(MAX2837_FT_5M);
+
 	max2837_regs_commit();
 }
 
@@ -192,10 +197,7 @@ void max2837_tx(void)
 	LOG("# max2837_tx\n");
 #if !defined TEST
 
-	/* configure baseband filter for 8 MHz TX */
-	set_MAX2837_LPF_EN(1);
 	set_MAX2837_ModeCtrl(MAX2837_ModeCtrl_TxLPF);
-	set_MAX2837_FT(MAX2837_FT_8M);
 	max2837_regs_commit();
 
 	gpio_set(PORT_XCVR_ENABLE, PIN_XCVR_TXENABLE);
@@ -206,10 +208,7 @@ void max2837_rx(void)
 {
 	LOG("# max2837_rx\n");
 
-	/* configure baseband filter for 8 MHz RX */
-	set_MAX2837_LPF_EN(1);
 	set_MAX2837_ModeCtrl(MAX2837_ModeCtrl_RxLPF);
-	set_MAX2837_FT(MAX2837_FT_8M);
 	max2837_regs_commit();
 
 #if !defined TEST
@@ -290,6 +289,49 @@ void max2837_set_frequency(uint32_t freq)
 	max2837_regs_commit();
 }
 
+typedef struct {
+	uint32_t bandwidth_hz;
+	uint32_t ft;
+} max2837_ft_t;
+
+static const max2837_ft_t max2837_ft[] = {
+	{  1750000, MAX2837_FT_1_75M },
+	{  2500000, MAX2837_FT_2_5M },
+	{  3500000, MAX2837_FT_3_5M },
+	{  5000000, MAX2837_FT_5M },
+	{  5500000, MAX2837_FT_5_5M },
+	{  6000000, MAX2837_FT_6M },
+	{  7000000, MAX2837_FT_7M },
+	{  8000000, MAX2837_FT_8M },
+	{  9000000, MAX2837_FT_9M },
+	{ 10000000, MAX2837_FT_10M },
+	{ 12000000, MAX2837_FT_12M },
+	{ 14000000, MAX2837_FT_14M },
+	{ 15000000, MAX2837_FT_15M },
+	{ 20000000, MAX2837_FT_20M },
+	{ 24000000, MAX2837_FT_24M },
+	{ 28000000, MAX2837_FT_28M },
+	{        0, 0 },
+};
+
+bool max2837_set_lpf_bandwidth(const uint32_t bandwidth_hz) {
+	const max2837_ft_t* p = max2837_ft;
+	while( p->bandwidth_hz != 0 ) {
+		if( p->bandwidth_hz >= bandwidth_hz ) {
+			break;
+		}
+		p++;
+	}
+	
+	if( p->bandwidth_hz != 0 ) {
+		set_MAX2837_FT(p->ft);
+		max2837_regs_commit();
+		return true;
+	} else {
+		return false;
+	}
+}
+
 #ifdef TEST
 int main(int ac, char **av)
 {

firmware/common/max2837.h

@@ -1,6 +1,9 @@
 #ifndef __MAX2837_H
 #define __MAX2837_H
 
+#include <stdint.h>
+#include <stdbool.h>
+
 /* TODO - make this a private header for max2837.c only, make new max2837.h */
 
 /* 32 registers, each containing 10 bits of data. */
@@ -40,6 +43,7 @@ extern void max2837_stop(void);
 /* Set frequency in Hz. Frequency setting is a multi-step function
  * where order of register writes matters. */
 extern void max2837_set_frequency(uint32_t freq);
+bool max2837_set_lpf_bandwidth(const uint32_t bandwidth_hz);
 
 extern void max2837_tx(void);
 extern void max2837_rx(void);

firmware/usb_performance/usb_performance.c

@@ -309,6 +309,22 @@ bool usb_vendor_request_set_sample_rate(
 	}
 }
 
+bool usb_vendor_request_set_baseband_filter_bandwidth(
+	usb_endpoint_t* const endpoint,
+	const usb_transfer_stage_t stage
+) {
+	if( stage == USB_TRANSFER_STAGE_SETUP ) {
+		const uint32_t bandwidth = (endpoint->setup.index << 16) | endpoint->setup.value;
+		if( baseband_filter_bandwidth_set(bandwidth) ) {
+			usb_endpoint_schedule_ack(endpoint->in);
+			return true;
+		}
+		return false;
+	} else {
+		return true;
+	}
+}
+
 void usb_vendor_request(
 	usb_endpoint_t* const endpoint,
 	const usb_transfer_stage_t stage
@@ -340,6 +356,10 @@ void usb_vendor_request(
 		success = usb_vendor_request_set_sample_rate(endpoint, stage);
 		break;
 
+	case 7:
+		success = usb_vendor_request_set_baseband_filter_bandwidth(endpoint, stage);
+		break;
+		
 	default:
 		break;
 	}

host/libhackrf/examples/hackrf_transfer.c

@@ -171,6 +171,12 @@ int main(int argc, char** argv) {
 		return -1;
 	}
 	
+	result = hackrf_baseband_filter_bandwidth_set(device, 5000000);
+	if( result != HACKRF_SUCCESS ) {
+		printf("hackrf_baseband_filter_bandwidth_set() failed: %s (%d)\n", hackrf_error_name(result), result);
+		return -1;
+	}
+	
 	if( transceiver_mode == TRANSCEIVER_MODE_RX ) {
 		result = hackrf_start_rx(device, rx_callback);
 	} else {

host/libhackrf/src/hackrf.c

@@ -35,6 +35,7 @@ typedef enum {
 	HACKRF_VENDOR_REQUEST_SI5351C_WRITE = 4,
 	HACKRF_VENDOR_REQUEST_SI5351C_READ = 5,
 	HACKRF_VENDOR_REQUEST_SAMPLE_RATE_SET = 6,
+	HACKRF_VENDOR_REQUEST_BASEBAND_FILTER_BANDWIDTH_SET = 7,
 } hackrf_vendor_request;
 
 typedef enum {
@@ -353,6 +354,25 @@ int hackrf_sample_rate_set(hackrf_device* device, const uint32_t sampling_rate_h
 	}
 }
 
+int hackrf_baseband_filter_bandwidth_set(hackrf_device* device, const uint32_t bandwidth_hz) {
+	int result = libusb_control_transfer(
+		device->usb_device,
+		LIBUSB_ENDPOINT_OUT | LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_RECIPIENT_DEVICE,
+		HACKRF_VENDOR_REQUEST_BASEBAND_FILTER_BANDWIDTH_SET,
+		bandwidth_hz & 0xffff,
+		bandwidth_hz >> 16,
+		NULL,
+		0,
+		0
+	);
+	
+	if( result != 0 ) {
+		return HACKRF_ERROR_LIBUSB;
+	} else {
+		return HACKRF_SUCCESS;
+	}
+}
+
 static void* transfer_threadproc(void* arg) {
 	hackrf_device* device = (hackrf_device*)arg;
 	

host/libhackrf/src/hackrf.h

@@ -68,6 +68,7 @@ int hackrf_si5351c_read(hackrf_device* device, uint16_t register_number, uint16_
 int hackrf_si5351c_write(hackrf_device* device, uint16_t register_number, uint16_t value);
 
 int hackrf_sample_rate_set(hackrf_device* device, const uint32_t sampling_rate_hz);
+int hackrf_baseband_filter_bandwidth_set(hackrf_device* device, const uint32_t bandwidth_hz);
 
 const char* hackrf_error_name(enum hackrf_error errcode);