add some uart flushes

src/radio.rs

@@ -28,6 +28,7 @@ impl UartRadio {
     pub fn send_packet(&mut self, packet: &FecPacket) -> anyhow::Result<()> {
         self.uart.write_all(&[SEND_PACKET_CMD])?;
         self.uart.write_all(&packet.0)?;
+        self.uart.flush()?;
 
         let mut buf = [0; 1];
         self.uart.read_exact(&mut buf)?;
@@ -48,6 +49,7 @@ impl UartRadio {
 
     pub fn get_temp(&mut self) -> anyhow::Result<f32> {
         self.uart.write_all(&[GET_TEMP_CMD])?;
+        self.uart.flush()?;
 
         let mut buf = [0; 4];
         self.uart.read_exact(&mut buf)?;