From f9b5d7b0a66b39d307334bb84a5ffa6b3171f7b8 Mon Sep 17 00:00:00 2001 From: Dimitri Stolnikov Date: Sun, 8 Jul 2012 15:52:59 +0200 Subject: [PATCH] apply frequency correction value on the xtal clock directly by using this approach both, the tuning frequency and the sample rate should be corrected at the same time. --- include/rtl-sdr.h | 17 ++++++++++-- src/librtlsdr.c | 71 +++++++++++++++++++++++++++++------------------ 2 files changed, 59 insertions(+), 29 deletions(-) diff --git a/include/rtl-sdr.h b/include/rtl-sdr.h index 7de8455..ec0b4c8 100644 --- a/include/rtl-sdr.h +++ b/include/rtl-sdr.h @@ -60,9 +60,9 @@ RTLSDR_API int rtlsdr_close(rtlsdr_dev_t *dev); * * Usually both ICs use the same clock. Changing the clock may make sense if * you are applying an external clock to the tuner or to compensate the - * frequency (and samplerate) error caused by the original cheap crystal. + * frequency (and samplerate) error caused by the original (cheap) crystal. * - * NOTE: Call this function only if you know what you are doing. + * NOTE: Call this function only if you fully understand the implications. * * \param dev the device handle given by rtlsdr_open() * \param rtl_freq frequency value used to clock the RTL2832 in Hz @@ -109,8 +109,21 @@ RTLSDR_API int rtlsdr_set_center_freq(rtlsdr_dev_t *dev, uint32_t freq); */ RTLSDR_API uint32_t rtlsdr_get_center_freq(rtlsdr_dev_t *dev); +/*! + * Set the frequency correction value for the device. + * + * \param dev the device handle given by rtlsdr_open() + * \param ppm correction value in parts per million (ppm) + * \return 0 on success + */ RTLSDR_API int rtlsdr_set_freq_correction(rtlsdr_dev_t *dev, int ppm); +/*! + * Get actual frequency correction value of the device. + * + * \param dev the device handle given by rtlsdr_open() + * \return correction value in parts per million (ppm) + */ RTLSDR_API int rtlsdr_get_freq_correction(rtlsdr_dev_t *dev); enum rtlsdr_tuner { diff --git a/src/librtlsdr.c b/src/librtlsdr.c index 98cf272..b603ef6 100644 --- a/src/librtlsdr.c +++ b/src/librtlsdr.c @@ -91,7 +91,7 @@ void rtlsdr_set_gpio_bit(rtlsdr_dev_t *dev, uint8_t gpio, int val); int e4000_init(void *dev) { rtlsdr_dev_t* devt = (rtlsdr_dev_t*)dev; devt->e4k_s.i2c_addr = E4K_I2C_ADDR; - devt->e4k_s.vco.fosc = devt->tun_xtal; + devt->e4k_s.vco.fosc = devt->tun_xtal; /* no need to correct it here */ devt->e4k_s.rtl_dev = dev; return e4k_init(&devt->e4k_s); } @@ -540,10 +540,7 @@ int rtlsdr_set_xtal_freq(rtlsdr_dev_t *dev, uint32_t rtl_freq, uint32_t tuner_fr (rtl_freq < MIN_RTL_XTAL_FREQ || rtl_freq > MAX_RTL_XTAL_FREQ)) return -2; - if (dev->rtl_xtal != rtl_freq) { - if (0 == rtl_freq) - rtl_freq = DEF_RTL_XTAL_FREQ; - + if (rtl_freq > 0 && dev->rtl_xtal != rtl_freq) { dev->rtl_xtal = rtl_freq; /* update xtal-dependent settings */ @@ -553,9 +550,13 @@ int rtlsdr_set_xtal_freq(rtlsdr_dev_t *dev, uint32_t rtl_freq, uint32_t tuner_fr if (dev->tun_xtal != tuner_freq) { if (0 == tuner_freq) - tuner_freq = dev->rtl_xtal; + dev->tun_xtal = dev->rtl_xtal; + else + dev->tun_xtal = tuner_freq; - dev->tun_xtal = tuner_freq; + /* read corrected clock value into e4k structure */ + if (rtlsdr_get_xtal_freq(dev, NULL, &dev->e4k_s.vco.fosc)) + return -3; /* update xtal-dependent settings */ if (dev->freq) @@ -570,12 +571,13 @@ int rtlsdr_get_xtal_freq(rtlsdr_dev_t *dev, uint32_t *rtl_freq, uint32_t *tuner_ if (!dev) return -1; - *rtl_freq = dev->rtl_xtal; + #define APPLY_PPM_CORR(val,ppm) (((val) * (1.0 + (ppm) / 1e6))) - if (!dev->tuner) - return -2; + if (rtl_freq) + *rtl_freq = (uint32_t) APPLY_PPM_CORR(dev->rtl_xtal, dev->corr); - *tuner_freq = dev->tun_xtal; + if (tuner_freq) + *tuner_freq = (uint32_t) APPLY_PPM_CORR(dev->tun_xtal, dev->corr); return 0; } @@ -624,16 +626,13 @@ int rtlsdr_get_usb_strings(rtlsdr_dev_t *dev, char *manufact, char *product, int rtlsdr_set_center_freq(rtlsdr_dev_t *dev, uint32_t freq) { int r = -1; - double f = (double) freq; if (!dev || !dev->tuner) return -1; if (dev->tuner->set_freq) { - f *= 1.0 + dev->corr / 1e6; - rtlsdr_set_i2c_repeater(dev, 1); - r = dev->tuner->set_freq(dev, (uint32_t) f); + r = dev->tuner->set_freq(dev, freq); rtlsdr_set_i2c_repeater(dev, 0); if (!r) @@ -647,7 +646,7 @@ int rtlsdr_set_center_freq(rtlsdr_dev_t *dev, uint32_t freq) uint32_t rtlsdr_get_center_freq(rtlsdr_dev_t *dev) { - if (!dev || !dev->tuner) + if (!dev) return 0; return dev->freq; @@ -655,25 +654,32 @@ uint32_t rtlsdr_get_center_freq(rtlsdr_dev_t *dev) int rtlsdr_set_freq_correction(rtlsdr_dev_t *dev, int ppm) { - int r; + int r = 0; - if (!dev || !dev->tuner) + if (!dev) return -1; if (dev->corr == ppm) - return -1; + return -2; dev->corr = ppm; - /* retune to apply new correction value */ - r = rtlsdr_set_center_freq(dev, dev->freq); + /* read corrected clock value into e4k structure */ + if (rtlsdr_get_xtal_freq(dev, NULL, &dev->e4k_s.vco.fosc)) + return -3; + + if (dev->rate) /* reset sample rate to apply new correction value */ + r |= rtlsdr_set_sample_rate(dev, dev->rate); + + if (dev->freq) /* retune to apply new correction value */ + r |= rtlsdr_set_center_freq(dev, dev->freq); return r; } int rtlsdr_get_freq_correction(rtlsdr_dev_t *dev) { - if (!dev || !dev->tuner) + if (!dev) return 0; return dev->corr; @@ -752,7 +758,7 @@ int rtlsdr_set_tuner_gain(rtlsdr_dev_t *dev, int gain) int rtlsdr_get_tuner_gain(rtlsdr_dev_t *dev) { - if (!dev || !dev->tuner) + if (!dev) return 0; return dev->gain; @@ -796,6 +802,7 @@ int rtlsdr_set_sample_rate(rtlsdr_dev_t *dev, uint32_t samp_rate) uint16_t tmp; uint32_t rsamp_ratio; double real_rate; + uint32_t rtl_freq; if (!dev) return -1; @@ -804,10 +811,14 @@ int rtlsdr_set_sample_rate(rtlsdr_dev_t *dev, uint32_t samp_rate) if (samp_rate > MAX_SAMP_RATE) samp_rate = MAX_SAMP_RATE; - rsamp_ratio = (dev->rtl_xtal * TWO_POW(22)) / samp_rate; + /* read corrected clock value */ + if (rtlsdr_get_xtal_freq(dev, &rtl_freq, NULL)) + return -2; + + rsamp_ratio = (rtl_freq * TWO_POW(22)) / samp_rate; rsamp_ratio &= ~3; - real_rate = (dev->rtl_xtal * TWO_POW(22)) / rsamp_ratio; + real_rate = (rtl_freq * TWO_POW(22)) / rsamp_ratio; if ( ((double)samp_rate) != real_rate ) fprintf(stderr, "Exact sample rate is: %f Hz\n", real_rate); @@ -1089,7 +1100,7 @@ found: } dev->tuner = &tuners[dev->tuner_type]; - dev->tun_xtal = dev->rtl_xtal; + dev->tun_xtal = dev->rtl_xtal; /* use the rtl clock value by default */ if (dev->tuner->init) r = dev->tuner->init(dev); @@ -1313,10 +1324,16 @@ int rtlsdr_cancel_async(rtlsdr_dev_t *dev) uint32_t rtlsdr_get_tuner_clock(void *dev) { + uint32_t tuner_freq; + if (!dev) return 0; - return ((rtlsdr_dev_t *)dev)->tun_xtal; + /* read corrected clock value */ + if (rtlsdr_get_xtal_freq((rtlsdr_dev_t *)dev, NULL, &tuner_freq)) + return 0; + + return tuner_freq; } int rtlsdr_i2c_write_fn(void *dev, uint8_t addr, uint8_t *buf, int len)