Implement tuner gain setters/getters

src/RTLSDR.jl

@@ -15,6 +15,9 @@ export
     set_rate,
     get_freq,
     set_freq,
+    get_gains,
+    get_gain,
+    set_gain,
     set_agc_mode,
     set_tuner_gain_mode
 
@@ -24,8 +27,8 @@ mutable struct RtlSdr
     valid_ptr::Bool
     dongle_ptr::Ptr{rtlsdr_dev}
 
-    function RtlSdr()
-        dp = rtlsdr_open()
+    function RtlSdr(index::Int64=0)
+        dp = rtlsdr_open(index)
 
         r = new(true, dp)
 
@@ -73,6 +76,35 @@ function get_freq(r::RtlSdr)
     return Int(freq)
 end
 
+"""
+`get_gains(r::RtlSdr)`
+
+Interface for `rtlsdr_get_tuner_gains`.
+Gains are in tenths of a dB.
+"""
+function get_gains(r::RtlSdr)
+    @assert r.valid_ptr
+    return rtlsdr_get_tuner_gains(r.dongle_ptr)
+end
+
+"""
+`set_gain(r::RtlSdr, gain_db)`
+
+Interface for `rtlsdr_set_tuner_gain`.
+"""
+function set_gain(r::RtlSdr, gain_db)
+    @assert r.valid_ptr
+    # Implement rounding, taking after roger-'s pyrtlsdr
+    avail_gains = get_gains(r)
+    errors = [abs((10 * gain_db) - avail_gain) for avail_gain in get_gains(r)]
+    closest_gain_idx = findall(errors .== minimum(errors))[1] # broadcast find
+    rtlsdr_set_tuner_gain(r.dongle_ptr, avail_gains[closest_gain_idx])
+end
+function get_gain(r::RtlSdr)
+    @assert r.valid_ptr
+    return rtlsdr_get_tuner_gain(r.dongle_ptr) / 10
+end
+
 """
 Interface for `rtlsdr_set_agc_mode`
 """

src/c_interface.jl

@@ -11,8 +11,7 @@ mutable struct RTLSDRError <: Exception
 end
 
 # returns a pointer to 
-function rtlsdr_open()
-    index = 0
+function rtlsdr_open(index::Int64=0)
     rd = Array{Ptr{rtlsdr_dev},1}(undef,1)
     ret = ccall( (:rtlsdr_open, "librtlsdr"),
                  Cint,
@@ -83,14 +82,41 @@ function rtlsdr_set_sample_rate(rf::Ref{rtlsdr_dev}, sample_rate)
 end
 
 # gain
-function rtlsdr_set_agc_mode(rf::Ref{rtlsdr_dev}, on)
+function rtlsdr_set_tuner_gain(rf::Ref{rtlsdr_dev}, gain)
     ret = ccall( (:rtlsdr_set_tuner_gain, "librtlsdr"),
                  Cint,
                  (Ref{rtlsdr_dev},Cint),
-                 rf, 
-                 on
+                 rf,
+                 gain
+               )
+    if ret != 0; throw(RTLSDRError("RTLSDR.jl reports: Error setting tuner gain (error code $ret).")); end
+end
+
+function rtlsdr_get_tuner_gain(rf::Ref{rtlsdr_dev})
+    gain = ccall( (:rtlsdr_get_tuner_gain, "librtlsdr"),
+                 Cint,
+                 (Ref{rtlsdr_dev},),
+                 rf
+               )
+    return gain[1]
+end
+
+function rtlsdr_get_tuner_gains(rf::Ref{rtlsdr_dev})
+    buf = Vector{Cint}(undef, 50) # max 50 gain settings. no RTL has this many.
+    num_gains = ccall( (:rtlsdr_get_tuner_gains, "librtlsdr"),
+                 Cint,
+                 (Ref{rtlsdr_dev}, Ref{Cint}),
+                 rf,
+                 buf
                 )
-    if ret != 0; throw(RTLSDRError("RTLSDR.jl reports: Error setting AGC mode (error code $ret).")); end
+    if num_gains == 0
+        throw(RTLSDRError("RTLSDR.jl reports: Error getting gains."))
+    end
+    avail_gains = Vector{Int32}(undef, num_gains)
+    for i = 1:num_gains
+        avail_gains[i] = buf[i]
+    end
+    return avail_gains
 end
 
 function rtlsdr_set_tuner_gain_mode(rf::Ref{rtlsdr_dev}, manual)
@@ -103,29 +129,17 @@ function rtlsdr_set_tuner_gain_mode(rf::Ref{rtlsdr_dev}, manual)
     if ret != 0; throw(RTLSDRError("RTLSDR.jl reports: Error setting tuner gain mode (error code $ret).")); end
 end
 
-function rtlsdr_set_tuner_gain(rf::Ref{rtlsdr_dev}, gain)
+function rtlsdr_set_agc_mode(rf::Ref{rtlsdr_dev}, on)
     ret = ccall( (:rtlsdr_set_tuner_gain, "librtlsdr"),
                  Cint,
                  (Ref{rtlsdr_dev},Cint),
-                 rf,
-                 gain
-               )
-    if ret != 0; throw(RTLSDRError("RTLSDR.jl reports: Error setting tuner gain (error code $ret).")); end
-end
-
-function rtlsdr_get_tuner_gain(rf::Ref{rtlsdr_dev})
-    gain = Array{Cint,1}(undef,1)
-    ret = ccall( (:rtlsdr_get_tuner_gain, "librtlsdr"),
-                 Cint,
-                 (Ref{rtlsdr_dev},Ptr{Cint}),
-                 rf,
-                 gain
-               )
-    if ret != 0; throw(RTLSDRError("RTLSDR.jl reports: Error getting tuner gain (error code $ret).")); end
-    return gain[1]
+                 rf, 
+                 on
+                )
+    if ret != 0; throw(RTLSDRError("RTLSDR.jl reports: Error setting AGC mode (error code $ret).")); end
 end
 
-
+# reading
 function read_bytes(rf::Ref{rtlsdr_dev}, num_bytes)
     buf = Vector{Cuchar}(undef,num_bytes)
     bytes_read = Ref{Cint}(0)