implement commands and turn everything on

Turn the modem on by setting appropriate pins to high/low.

Implemented all commands from
https://github.com/pythings/Drivers/blob/master/SIM800L.py#L116-L143 in Rust.

Moved AP values to a config module. Maybe create a build environment for this
later on, we'll need to support multiple telecom providers for sure ...

Fix the write/read implementation for the Serial. Match on end and handle the
timeout properly for every command.

src/command.rs

@@ -0,0 +1,219 @@
+#[allow(dead_code)]
+
+use std::time::Duration;
+
+pub struct Command {
+    pub text: String,
+    pub timeout: Duration,
+    pub ends_with: Option<String>,
+}
+
+impl Command {
+    pub fn initgprs() -> Command {
+        Command {
+            text: "AT+SAPBR=3,1,\"Contype\",\"GPRS\"".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn modeminfo() -> Command {
+        Command {
+            text: "ATI".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn fwrevision() -> Command {
+        Command {
+            text: "AT+CGMR".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn battery() -> Command {
+        Command {
+            text: "AT+CBC".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn scan() -> Command {
+        Command {
+            text: "AT+COPS=?".to_owned(),
+            timeout: Duration::from_millis(60),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn network() -> Command {
+        Command {
+            text: "AT+COPS?".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn signal() -> Command {
+        Command {
+            text: "AT+CSQ".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn checkreg() -> Command {
+        Command {
+            text: "AT+CREG?".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: None,
+        }
+    }
+
+    pub fn opengprs() -> Command {
+        Command {
+            text: "AT+SAPBR=1,1".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn getbear() -> Command {
+        Command {
+            text: "AT+SAPBR=2,1".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn inithttp() -> Command {
+        Command {
+            text: "AT+HTTPINIT".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn sethttp() -> Command {
+        Command {
+            text: "AT+HTTPPARA=\"CID\",1".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn checkssl() -> Command {
+        Command {
+            text: "AT+CIPSSL=?".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn enablessl() -> Command {
+        Command {
+            text: "AT+HTTPSSL=1".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn disablessl() -> Command {
+        Command {
+            text: "AT+HTTPSSL=0".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn initurl() -> Command {
+        Command {
+            text: "AT+HTTPPARA=\"URL\",\"{}\"".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn doget() -> Command {
+        Command {
+            text: "AT+HTTPACTION=0".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("+HTTPACTION".to_owned()),
+        }
+    }
+
+    pub fn setcontent() -> Command {
+        Command {
+            text: "AT+HTTPPARA=\"CONTENT\",\"{}\"".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn postlen() -> Command {
+        Command {
+            text: "AT+HTTPDATA={}5000".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("DOWNLOAD".to_owned()),
+        }
+    }
+
+    pub fn dopost() -> Command {
+        Command {
+            text: "AT+HTTPACTION=1".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("+HTTPACTION".to_owned()),
+        }
+    }
+
+    pub fn getdata() -> Command {
+        Command {
+            text: "AT+HTTPREAD".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn closehttp() -> Command {
+        Command {
+            text: "AT+HTTPTERM".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn closebear() -> Command {
+        Command {
+            text: "AT+SAPBR=0,1".to_owned(),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn setapn(apn: &str) -> Command {
+        Command {
+            text: format!("AT+SAPBR=3,1,\"APN\",\"{}\"", apn),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn setuser(user: &str) -> Command {
+        Command {
+            text: format!("AT+SAPBR=3,1,\"USER\",\"{}\"", user),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+
+    pub fn setpwd(password: &str) -> Command {
+        Command {
+            text: format!("AT+SAPBR=3,1,\"PWD\",\"{}\"", password),
+            timeout: Duration::from_millis(3),
+            ends_with: Some("OK".to_owned()),
+        }
+    }
+}