diff --git a/Cargo.toml b/Cargo.toml
index 5061f46..c77a2cc 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,11 +5,11 @@ edition = "2018"
 version = "0.1.0"
 
 [dependencies]
-cortex-m = "0.7.6"
+cortex-m = { version = "0.7.6", features = ["critical-section-single-core"]}
 cortex-m-rt = "0.7.2"
 cortex-m-rtic = "1.1.3"
 defmt = "0.3.2"
-defmt-rtt = "0.3.2"
+defmt-rtt = "0.4"
 panic-probe = { version = "0.3.0", features = ["print-defmt"] }
 stm32f1xx-hal = { version = "0.9.0", features = ["stm32f103", "rt", "medium"] }
 embedded-hal = {version = "0.2.3"}
diff --git a/src/main.rs b/src/main.rs
index c598944..48e6ee6 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -27,11 +27,11 @@ mod app {
         },
         i2c,
         i2c::BlockingI2c,
-        pac::{ADC1, I2C1, TIM4},
+        pac::{ADC1, I2C1, TIM2, TIM4},
         prelude::*,
         serial::{self, Config, Serial},
         stm32,
-        timer::{self, Channel, Event, Tim3NoRemap, Tim4NoRemap},
+        timer::{self, Channel, CounterHz, Event, Tim3NoRemap, Tim4NoRemap},
     };
 
     use systick_monotonic::Systick;
@@ -74,6 +74,7 @@ mod app {
         q_in: gpio::Pin<Analog, CRL, 'A', 0>,
         phase: f32,
         audio_pwm: AudioPwm,
+        timer: CounterHz<TIM2>,
     }
 
     #[init]
@@ -145,7 +146,7 @@ mod app {
         let mut audio_pwm = cx.device.TIM4.pwm_hz::<Tim4NoRemap, _, _>(
             audio_out,
             &mut afio.mapr,
-            4800.Hz(),
+            192.kHz(),
             &clocks,
         );
         audio_pwm.enable(Channel::C3);
@@ -180,16 +181,17 @@ mod app {
                 q_in,
                 phase: 0.0,
                 audio_pwm,
+                timer,
             },
             init::Monotonics(mono),
         )
     }
 
-    #[task(binds=TIM2, local=[pll, i2c, adc1, mic_in, i_in, q_in, audio_pwm, phase, board_led])]
+    #[task(binds=TIM2, local=[timer, pll, i2c, adc1, mic_in, i_in, q_in, audio_pwm, phase, board_led])]
     fn transmit(mut ctx: transmit::Context) {
-        *ctx.local.phase += core::f32::consts::PI * 2.0 * 1000.0 / 4800.0;
+        *ctx.local.phase += core::f32::consts::PI * 2.0 * 2000.0 / 4800.0;
         if *ctx.local.phase > 2.0 * core::f32::consts::PI {
-            *ctx.local.phase -= core::f32::consts::PI;
+            *ctx.local.phase -= 2.0 * core::f32::consts::PI;
             ctx.local.board_led.toggle();
         }
 
@@ -201,7 +203,9 @@ mod app {
             2.0.powi(16)
         };
 
-        let sample = (ctx.local.phase.sin() + 0.5) * max_duty;
+        let sample = (ctx.local.phase.sin() + 1.0) * max_duty / 2.0;
         ctx.local.audio_pwm.set_duty(Channel::C3, sample as u16);
+
+        ctx.local.timer.clear_interrupt(Event::Update);
     }
 }