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--- tutorials_contiki [2019/04/17 18:42]
dant created
+++ tutorials_contiki [2019/04/17 18:51] (current)
dant [Contiki OS and Sparrow]
@@ Line 1: / Line 1: @@
 ====== Contiki OS and Sparrow ======
-Contiki considers itself the "The Operating System for Connecting the Next Billion Devices - the Internet of Things." It's an Internet-connected multi-tasking OS for low-end platforms, like Microcontrollers. Contiki is great for the amazing level of connected functionality it will squeeze out of a five dollar chip. It runs on a vast array of platforms and CPU's.
+[[http://www.contiki-os.org/|Contiki]] considers itself the "The Operating System for Connecting the Next Billion Devices - the Internet of Things." It's an Internet-connected multi-tasking OS for low-end platforms, like Microcontrollers. Contiki is great for the amazing level of connected functionality it will squeeze out of a five dollar chip. It runs on a vast array of platforms and CPU's.
 ===== Installing Contiki =====
@@ Line 138: / Line 138: @@
 Responding with message: Hello from the server! (5)
 Server received: 'Hello 7 from the client' from fdfd::1 +OK PASS </code>
+====== Timers & Events in Contiki ======
+This tutorial will show how to make use of timers in Contiki. It will also give a basic into to events.
+===== Processes =====
+All Contiki programs are processes. A process is a piece of code that is executed regularly by the Contiki system. Processes in Contiki are typically started when the system boots, or when a module that contains a process is loaded into the system. Processes run when something happens, such as a timer firing or an external event occurring.
+Code in Contiki can run in one of two execution contexts: cooperative or preemptive. Code running in the cooperative execution context is run sequentially with respect to other code in the cooperative context. Cooperative code must run to completion before other cooperatively scheduled code can run. Preemptive code may stop the cooperative code at any time. When preemptive code stops the cooperative code, the cooperative code will not be resumed until the preemptive code has completed. The concept of Contiki's two scheduling contexts is illustrated above.
+Processes always run in the cooperative context. The preemptive context is used by interrupt handlers in device drivers and by real-time tasks that have been scheduled for a specific deadline.
+An example process that receives events and prints out their number:
+<code C>
+ #include "contiki.h"
+ PROCESS(example_process, "Example process");
+ AUTOSTART_PROCESSES(&example_process);
+ PROCESS_THREAD(example_process, ev, data)
+ {
+   PROCESS_BEGIN();
+   while(1) {
+     PROCESS_WAIT_EVENT();
+     printf("Got event number %d\n", ev);
+   }
+   PROCESS_END();
+ }
+</code>
+The complete reference on Contiki processes can be found [[https://github.com/contiki-os/contiki/wiki/Processes|here]].
+Contiki provides three kinds of timers:
+  * **Simple timer:** The timer library provides functions for setting, resetting and restarting timers, and for checking if a timer has expired. An application must "manually" check if its timers have expired, meaning that this library does not post an event when the timer expires, so we must implement a routine that checks the timer for expiration.
+  * **Callback timer:** The callback timer library provides the same functions as above, but when the timer expires can callback a C function.
+  * **Event timer:** The same as above, with the difference that instead of calling a function, when the timer expires it post an event signalling the timer expiration.
+More information on timer can be found on the Contiki's [[https://github.com/contiki-os/contiki/wiki/Timers|wiki page on timers]].
+===== The Event Timer =====
+The etimer (Event timer) will post an event when the timer is expiring. Since it posts an event you will need to have a process around it to handle the event.
+<code C>
+PROCESS_THREAD(etimer_process, ev, data)
+{
+  static struct etimer et;
+  PROCESS_BEGIN();
+  /* set timer to expire after 5 seconds */
+  etimer_set(&et, CLOCK_SECOND * 5);
+  while(1) {
+    PROCESS_WAIT_EVENT(); /* Same thing as PROCESS_YIELD */
+    if(etimer_expired(&et)) {
+      /* Do the work here and restart timer to get it periodic !!! */
+      printf("etimer expired.\n");
+      etimer_restart(&et);
+    }
+  }
+  PROCESS_END();
+}
+</code>
+In the above code the process is defined by PROCESS_THREAD which takes a name, an event variable and an event data variable as the arguments. When an etimer expires the event variable will be set to PROCESS_EVENT_TIMER and the event data variable will be set to point to the specific timer. Using that information the above example could also look like:
+<code C>
+PROCESS_WAIT_EVENT_UNTIL(ev == PROCESS_EVENT_TIMER && data == &et);
+/* Do the work here and restart timer to get it periodic! */
+printf("etimer expired.\n");
+etimer_restart(&et);
+</code>
+But when waiting for this event in this way -- all other events will be ignored so the first approach is more flexible as this will enable handling multiple types of events more easily.
 ===== The Shell =====
@@ Line 204: / Line 277: @@
 Other ICMP6 message received.
 Echo reply received. </code>
+====== Using SLIP ======
+===== What is SLIP? =====
+SLIP is the "mostly obsolete" wikipedia:Serial Line Internet Protocol. "On personal computers, SLIP has been largely replaced by the Point-to-Point Protocol (PPP), which is better engineered, has more features and does not require its IP address configuration to be set before it is established. On microcontrollers, however, SLIP is still the preferred way of encapsulating IP packets due to its very small overhead."
+Contiki uses SLIP to bridge the wireless IPv6 network onto a PC via a USB connection. So with your Sparrow plugged into your PC, and the right software running on each, traffic from the wireless IP network can reach your site-wide Ethernet network and potentially beyond.
+On Sparrow, there is only one UART exposed. This means we have to choose between reading debug messages and connecting to our PC via SLIP. This change is exposed by adding "WITH_SLIP=1" to the makefile or command line for any particular project. Projects made "WITH_SLIP" will expect to talk to a slip tunnel on the PC side.
+Speaking of the PC side... In order for SLIP to work, something on the host PC has to be listening. Using Instant Contiki, the 'tunslip6' will do this. Running it in Linux creates a 'tun0' interface which gives the connected Sparrow an address of aaaa::1 on your local network.
+===== Building =====
+First, built the tunslip6 tool. This works without modification on Instant Contiki.
+<code>
+$ cd tools
+$ make tunslip6 </code>
+Now make and upload the border router itself. Be sure to include "WITH_SLIP=1" to turn on slip for this node, and "WITH_WEBSERVER=0" to exclude a web server from this node.
+<code>
+$ cd examples/ipv6/rpl-border-router
+$ make TARGET=sparrow savetarget
+$ make WITH_SLIP=1 WITH_WEBSERVER=0 -j10
+$ make upload AVRDUDE_PORT=/dev/ttyUSB0 </code>
+===== Connecting =====
+Ok, now it's built. Let's bring up the slip interface on Linux. Note that the baud rate here has to match the baud rate in the uart setup on the board, which is currently 38400. That's a little slow, but I'll work on bringing it up in future revisions. Also note the "v6" switch. That turns on maximum debugging output so we can follow along.
+<code>$ sudo ../../../tools/tunslip6 aaaa::1/64 -s /dev/ttyUSB0 -B 38400 -v6
+********SLIP started on ``/dev/ttyUSB0 opened tun device ``/dev/tun0
+ifconfig tun0 inet `hostname` up
+ifconfig tun0 add aaaa::1/64
+ifconfig tun0
+tun0 Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
+     inet addr:127.0.1.1  P-t-P:127.0.1.1  Mask:255.255.255.255
+     inet6 addr: aaaa::1/64 Scope:Global
+     UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
+     RX packets:0 errors:0 dropped:0 overruns:0 frame:0
+     TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
+     collisions:0 txqueuelen:500    RX bytes:0 (0.0 B)     TX bytes:0 (0.0 B)
+tun0 Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
+     inet addr:127.0.0.1  P-t-P:127.0.0.1  Mask:255.255.255.255
+     inet6 addr: aaaa::1/64 Scope:Global
+     UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
+     RX packets:0 errors:0 dropped:0 overruns:0 frame:0
+     TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
+     collisions:0 txqueuelen:500
+     RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
+IP addresses [4 max] fdfd::3 fe80::11:22ff:fe33:4403 RPL-Border router started
+*** Address:aaaa::1 => aaaa:0000:0000:0000 SIN: 10 Got configuration message of type P
+Setting prefix aaaa:: created a new RPL dag Server IPv6 addresses:  aaaa::11:22ff:fe33:4403
+fdfd::3  fe80::11:22ff:fe33:4403 </code>
+It's helpful that tunslip6 is putting through the debug messages from the Sparrow. So we can see the boot-up process complete successfully.
+===== Ping =====
+We should now be able to ping the border router from the host PC. First, we can ping its auto-configured aaaa::/64 address
+<code>$ ping6 aaaa::11:22ff:fe33:4403
+PING aaaa::11:22ff:fe33:4403(aaaa::11:22ff:fe33:4403) 56 data bytes
+bytes from aaaa::11:22ff:fe33:4403: icmp_seq=1 ttl=64 time=66.1 ms
+bytes from aaaa::11:22ff:fe33:4403: icmp_seq=2 ttl=64 time=68.6 ms
+bytes from aaaa::11:22ff:fe33:4403: icmp_seq=3 ttl=64 time=66.2 ms</code>
+===== Nodes Beyond the Border =====
+We want to reach more nodes than just the one connected. So let's add a route on the host PC. This "route add" command tells Ubuntu that whenever it wants to reach a node whose IP starts with fdfd::/64, it can send that through the tun0 interface.
+<code>
+$ sudo route -A inet6 add fdfd::/64 dev tun0
+$ netstat -r6 Kernel IPv6 routing table
+Destination                    Next Hop                   Flag Met Ref Use If
+aaaa::/64                      ::                         U    256 0     0 tun0
+fdfd::/64                      ::                         U    1   0     0 tun0 </code>
+Now that we have the route set up, we can put another node on the network, and ping that.
+Put anything that speaks RPL on fdfd::1, for example rpl-collect/sender
+<code>$ cd examples/ipv6/rpl-collect
+$ make TARGET=sparrow savetarget
+$ make udp-sender.sparrow.u AVRDUDE_PORT=/dev/ttyUSB1 -j10 </code>
+Now see that we can ping it ok:
+<code>$ ping6 fdfd::1 PING fdfd::1(fdfd::1) 56 data bytes
+bytes from fdfd::1: icmp_seq=1 ttl=64 time=67.8 ms
+bytes from fdfd::1: icmp_seq=2 ttl=64 time=66.3 ms</code>
+====== Using the Webserver ======
+From a PC on our network, we want to view a web page served up by any node on our wireless IP network. This will allow us to look at sensor values or other data stored there.
+===== Building =====
+We'll put the rpl-border-router (with no webserver) on the node connected to the PC, and talk SLIP over USB between it and the PC. The other node will run webserver-ipv6 with 'webserver-nano'.
+<code>$ cd examples/ipv6/rpl-border-router
+$ make TARGET=sparrow savetarget
+$ make upload WITH_WEBSERVER=0 WITH_SLIP=1 AVRDUDE_PORT=/dev/ttyUSB0 -j10
+$ cd examples/webserver-ipv6
+$ make TARGET=sparrow savetarget
+$ make WITH_WEBSERVER=webserver-nano -j10
+$ make upload login WITH_WEBSERVER=webserver-nano AVRDUDE_PORT=/dev/ttyUSB1 </code>
+===== Running =====
+This has to be done in another window, because "make login" above took over that window. Here we will bring up the tunnel, and try everything out, one thing at a time. Ping the router, ping the webserver, do the 'get'.
+<code>$ sudo ../../../tools/tunslip6 aaaa::1/64 -s /dev/ttyUSB0 -B 38400 -v6
+$ sudo route -A inet6 add fdfd::/64 dev tun0
+$ ping6 fdfd::3 $ ping6 fdfd::1
+$ curl -g "http://[aaaa::11:22ff:fe33:4401]/" </code>
+Here's what success looks like!
+<code>$ curl -g "http://[aaaa::11:22ff:fe33:4401]/" <html> <head> <title>Contiki-nano</title> </head> <body> <pre> <a href="/">Front page</a>| <a href="status.shtml">Status</a>| <a href="tcp.shtml">Network connections</a>| <a href="processes.shtml">System processes</a>| <a href="files.shtml">File statistics</a>| <a href="/ttt/ttt.shtml">TicTacToe</a> </pre> Welcome to the <a href="http://www.sics.se/contiki/">Contiki</a>  nano web server!<p align="right"> <br><br> <i>This page has been sent 2 times</i> </body> </html> </code>
+Plus here's the Wireshark summary of this conversation:
+<code>
+ No.     Time        Source                Destination           Protocol Info
+0.000000    aaaa::1               aaaa::11:22ff:fe33:4401 TCP      36067 > http [SYN] Seq=0 Win=5760 Len=0 MSS=1440 TSV=87387016 TSER=0 WS=5
+0.242296    aaaa::11:22ff:fe33:4401 aaaa::1               TCP      http > 36067 [SYN, ACK] Seq=0 Ack=1 Win=1220 Len=0 MSS=1220
+0.242351    aaaa::1               aaaa::11:22ff:fe33:4401 TCP      36067 > http [ACK] Seq=1 Ack=1 Win=5760 Len=0
+0.242589    aaaa::1               aaaa::11:22ff:fe33:4401 HTTP     GET / HTTP/1.1
+0.630341    aaaa::11:22ff:fe33:4401 aaaa::1               TCP      [TCP segment of a reassembled PDU]
+0.630388    aaaa::1               aaaa::11:22ff:fe33:4401 TCP      36067 > http [ACK] Seq=165 Ack=86 Win=5760 Len=0
+0.898326    aaaa::11:22ff:fe33:4401 aaaa::1               TCP      [TCP segment of a reassembled PDU]
+0.898360    aaaa::1               aaaa::11:22ff:fe33:4401 TCP      36067 > http [ACK] Seq=165 Ack=113 Win=5760 Len=0
+1.258323    aaaa::11:22ff:fe33:4401 aaaa::1               TCP      [TCP segment of a reassembled PDU]
+1.258369    aaaa::1               aaaa::11:22ff:fe33:4401 TCP      36067 > http [ACK] Seq=165 Ack=408 Win=6432 Len=0
+1.550390    aaaa::11:22ff:fe33:4401 aaaa::1               TCP      [TCP segment of a reassembled PDU]
+1.550426    aaaa::1               aaaa::11:22ff:fe33:4401 TCP      36067 > http [ACK] Seq=165 Ack=490 Win=6432 Len=0
+1.842334    aaaa::11:22ff:fe33:4401 aaaa::1               TCP      [TCP segment of a reassembled PDU]
+1.842364    aaaa::1               aaaa::11:22ff:fe33:4401 TCP      36067 > http [ACK] Seq=165 Ack=567 Win=6432 Len=0
+2.098333    aaaa::11:22ff:fe33:4401 aaaa::1               TCP      http > 36067 [FIN, ACK] Seq=567 Ack=165 Win=1220 Len=0
+2.098508    aaaa::1               aaaa::11:22ff:fe33:4401 TCP      36067 > http [FIN, ACK] Seq=165 Ack=568 Win=6432 Len=0
+2.334295    aaaa::11:22ff:fe33:4401 aaaa::1               TCP      http > 36067 [ACK] Seq=568 Ack=166 Win=1220 Len=0 </code>