From 416d6c4f9768f22e7b4cfdd684c58df17c946dbc Mon Sep 17 00:00:00 2001
From: "Christian W. Zuckschwerdt" <christian@zuckschwerdt.org>
Date: Tue, 7 Feb 2023 18:18:48 +0100
Subject: [PATCH] minor: Add RTL-SDR settings option help

---
 README.md          | 5 +++--
 man/man1/rtl_433.1 | 5 +++--
 src/rtl_433.c      | 5 +++--
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/README.md b/README.md
index 76dd630e9..85e4b9a38 100644
--- a/README.md
+++ b/README.md
@@ -45,8 +45,9 @@ See [CONTRIBUTING.md](./docs/CONTRIBUTING.md).
 		= Tuner options =
   [-d <RTL-SDR USB device index> | :<RTL-SDR USB device serial> | <SoapySDR device query> | rtl_tcp | help]
   [-g <gain> | help] (default: auto)
-  [-t <settings>] apply a list of keyword=value settings for SoapySDR devices
-       e.g. -t "antenna=A,bandwidth=4.5M,rfnotch_ctrl=false"
+  [-t <settings>] apply a list of keyword=value settings to the SDR device
+       e.g. for SoapySDR -t "antenna=A,bandwidth=4.5M,rfnotch_ctrl=false"
+       for RTL-SDR use "direct_samp[=1]", "offset_tune[=1]", "digital_agc[=1]", "biastee[=1]"
   [-f <frequency>] Receive frequency(s) (default: 433920000 Hz)
   [-H <seconds>] Hop interval for polling of multiple frequencies (default: 600 seconds)
   [-p <ppm_error>] Correct rtl-sdr tuner frequency offset error (default: 0)
diff --git a/man/man1/rtl_433.1 b/man/man1/rtl_433.1
index c8ced5aff..60fb9fda4 100644
--- a/man/man1/rtl_433.1
+++ b/man/man1/rtl_433.1
@@ -54,8 +54,9 @@ Read config options from a file
 [\-g <gain> | help] (default: auto)
 .TP
 [ \fB\-t\fI <settings>\fP ]
-apply a list of keyword=value settings for SoapySDR devices
-       e.g. \-t "antenna=A,bandwidth=4.5M,rfnotch_ctrl=false"
+apply a list of keyword=value settings to the SDR device
+       e.g. for SoapySDR \-t "antenna=A,bandwidth=4.5M,rfnotch_ctrl=false"
+       for RTL\-SDR use "direct_samp[=1]", "offset_tune[=1]", "digital_agc[=1]", "biastee[=1]"
 .TP
 [ \fB\-f\fI <frequency>\fP ]
 Receive frequency(s) (default: 433920000 Hz)
diff --git a/src/rtl_433.c b/src/rtl_433.c
index c6fcf2b9b..a89b24a66 100644
--- a/src/rtl_433.c
+++ b/src/rtl_433.c
@@ -145,8 +145,9 @@ static void usage(int exit_code)
             "\t\t= Tuner options =\n"
             "  [-d <RTL-SDR USB device index> | :<RTL-SDR USB device serial> | <SoapySDR device query> | rtl_tcp | help]\n"
             "  [-g <gain> | help] (default: auto)\n"
-            "  [-t <settings>] apply a list of keyword=value settings for SoapySDR devices\n"
-            "       e.g. -t \"antenna=A,bandwidth=4.5M,rfnotch_ctrl=false\"\n"
+            "  [-t <settings>] apply a list of keyword=value settings to the SDR device\n"
+            "       e.g. for SoapySDR -t \"antenna=A,bandwidth=4.5M,rfnotch_ctrl=false\"\n"
+            "       for RTL-SDR use \"direct_samp[=1]\", \"offset_tune[=1]\", \"digital_agc[=1]\", \"biastee[=1]\"\n"
             "  [-f <frequency>] Receive frequency(s) (default: %i Hz)\n"
             "  [-H <seconds>] Hop interval for polling of multiple frequencies (default: %i seconds)\n"
             "  [-p <ppm_error>] Correct rtl-sdr tuner frequency offset error (default: 0)\n"