diff --git a/sndlock.cpp b/sndlock.cpp
index 01b6b88..42acbd4 100644
--- a/sndlock.cpp
+++ b/sndlock.cpp
@@ -17,6 +17,7 @@ static std::atomic<float> frequency = 440.0f;
 #define SND_SIG 1
 #define SND_BITS 16
 #define SND_PCHAN 2
+#define SND_RCHAN 1
 #define SND_RATE 44100
 #define SND_BUFLEN 4096
 
@@ -25,7 +26,7 @@ static void dsp_thread()
     struct sio_hdl *hdl;
     struct sio_par par;
 
-    hdl = sio_open(SIO_DEVANY, SIO_PLAY, 1);
+    hdl = sio_open(SIO_DEVANY, SIO_PLAY|SIO_REC, 1);
     if(hdl == nullptr) {
         std::cerr << "failed to open sound device" << std::endl;
         return;
@@ -34,6 +35,7 @@ static void dsp_thread()
     par.sig = SND_SIG;
     par.bits = SND_BITS;
     par.pchan = SND_PCHAN;
+    par.pchan = SND_RCHAN;
     par.rate = SND_RATE;
     par.le = SIO_LE_NATIVE;
     par.xrun = SIO_ERROR;
@@ -60,14 +62,15 @@ static void dsp_thread()
     size_t buf_out_idx = SND_BUFLEN*SND_PCHAN;
     nfds_t nfds = sio_nfds(hdl);
     struct pollfd pfd[nfds];
+
     while(!shutdown_threads) {
-        sio_pollfd(hdl, pfd, POLLOUT);
+        sio_pollfd(hdl, pfd, POLLOUT|POLLIN);
         poll(pfd, nfds, INFTIM);
         int revents = sio_revents(hdl, pfd);
 
         if(revents & POLLOUT) {
-            uint32_t ftw = frequency*(float)UINT32_MAX/SND_RATE;
             if(buf_out_idx == SND_BUFLEN*SND_PCHAN) {
+                uint32_t ftw = frequency*(float)UINT32_MAX/SND_RATE;
                 for(int i=0;i<SND_BUFLEN;i++) {
                     buf_out[2*i] = buf_out[2*i+1] = (INT16_MAX-1)*sin(phase*2.0f*(float)M_PI/(float)UINT32_MAX);
                     phase += ftw;
@@ -76,12 +79,14 @@ static void dsp_thread()
             }
             size_t written = sio_write(hdl, &buf_out[buf_out_idx], sizeof(buf_out) - buf_out_idx*sizeof(buf_out[0]));
             buf_out_idx += written/sizeof(buf_out[0]);
-            if(!written) {
-                std::cerr << "failed to write to sound device" << std::endl;
-                sio_stop(hdl);
-                sio_close(hdl);
-                return;
-            }
+        }
+
+        if(revents & POLLIN) {
+            int16_t buf_in[SND_BUFLEN*SND_RCHAN];
+            sio_read(hdl, buf_in, sizeof(buf_in));
+            for(int i=0;i<10;i++)
+              std::cout << buf_in[i] << " ";
+            std::cout << std::endl;
         }
     }