Interpret last four bytes of EEPROM as value in Hz using network byte order and use it as default if it is between MIN_RTL_XTAL_FREQ and MAX_RTL_XTAL_FREQ. --- src/librtlsdr.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/src/librtlsdr.c b/src/librtlsdr.c index 2f5d90a..c986018 100644 --- a/src/librtlsdr.c +++ b/src/librtlsdr.c @@ -25,6 +25,9 @@ #ifndef _WIN32 #include <unistd.h> #define min(a, b) (((a) < (b)) ? (a) : (b)) +#include <arpa/inet.h> +#else +#include <WinSock2.h> #endif

#include <libusb.h> @@ -279,6 +282,7 @@ static rtlsdr_dongle_t known_devices[] = { #define BULK_TIMEOUT 0

#define EEPROM_ADDR 0xa0 +#define EEPROM_SIZE 256

enum usb_reg { USB_SYSCTL = 0x2000, @@ -1365,14 +1369,27 @@ int rtlsdr_open(rtlsdr_dev_t **out_dev, uint32_t index) goto err; }

- dev->rtl_xtal = DEF_RTL_XTAL_FREQ; - /* perform a dummy write, if it fails, reset the device */ if (rtlsdr_write_reg(dev, USBB, USB_SYSCTL, 0x09, 1) < 0) { fprintf(stderr, "Resetting device...\n"); libusb_reset_device(dev->devh); }

+ dev->rtl_xtal = DEF_RTL_XTAL_FREQ; + + /* Allow for the last four bytes of the EEPROM to contain a + calibration frequency. */ + { + uint32_t rtl_freq; + + if (0 < rtlsdr_read_eeprom(dev, (void *)&rtl_freq, EEPROM_SIZE-4, 4)) + rtl_freq = ntohl(rtl_freq); + if (rtl_freq >= MIN_RTL_XTAL_FREQ && rtl_freq <= MAX_RTL_XTAL_FREQ) { + fprintf(stderr, "Found valid XTAL calibration in EEPROM: %u Hz\n", + dev->rtl_xtal = rtl_freq); + } + } + rtlsdr_init_baseband(dev); dev->dev_lost = 0;