turn on the modem first

src/main.rs

@@ -38,6 +38,9 @@ fn main() -> ! {
         io.pins.gpio27.into_floating_input(),
     );
 
+    let mut power = io.pins.gpio4.into_push_pull_output();
+    power.set_high().ok();
+
     let config = Config {
         baudrate: 115200,
         data_bits: DataBits::DataBits8,