print driven development

src/main.rs

@@ -1,5 +1,10 @@
+mod modem;
+
 use esp_idf_sys as _; // If using the `binstart` feature of `esp-idf-sys`, always keep this module imported
 
 fn main() {
-    println!("Hello, world!");
+    println!("Starting GPRS ...");
+    // TODO: start sim module
+    // TODO: connect to GPRS
+    println!("GPRS started ...");
 }

src/modem.rs

@@ -0,0 +1,3 @@
+pub struct Modem {
+    // TODO: connect to GPRS
+}