ELECINF344/381

Partie interactive du site pédagogique ELECINF344/ELECINF381 de Télécom ParisTech (occurrence 2011).

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TSV Safe Express: Big time troubleshooting.

Today we have faced numerous problems. The ethernet module causes a crash in our central station and we still haven’t figured out the solution. We also tried to connect all card’s (6 captor-6 traffic lights cards) to our main station and they failed to join our the network. As Alexis consulted us to do, we lowered the baud rate of the CAN bus so that problem is solved. All cards join the network and  CAN baud rate now is configured at 125kbp/s.

Regarding the communication of the server with the train we were able to track the position of the train and send it to the server. Our goal now is to remotely control lights and train, and we are working on it.

Wireless RoseWheel

After a long night of debugging, we finally managed to make the bluetooth working.  We are now able to send instruction and receive information from RoseWheel through the bluetooth interface using minicom on a laptop. We are also able to pair with an Android smartphone but we haven’t been able to verify the data transmission yet. We are still working on the Android application, but hopefully tomorrow we will be able to start our first tests of wireless communication with RoseWheel.

We also tested the  range of the Bluetooth with the transmitter inside the chassis and we received the signal from a distance of approximately 10 meters with two walls in between.

We started the implementation of the human-interface board. We have found a big LCD driven by the same controller as the one of our laboratory boards. We plan to use it to display information to the user directly on the handlebars, such as the engine power, battery level and the current angle measured by the sensors. As we are going to place the LCD vertically we had to rewrite a new set of characters made to be displayed in this orientation.

MB Led: Easter Saturday in A405

Today, we continued on our recent work : I worked on the algorithm and on the rotation of a block. The rotation works quite well now. The algorithm for this rotation is simple : When a communication between two blocks is stopped (due to the left of someone), the two blocks save their « interfaces » (aliases of the UARTs ). When there is a PING from a block, we check the saved interfaces in order to see if the block was a « friend » of this block. If it’s the case, we just calculate the rotation of the block.

The main problem is that a block can communicate with 4 others blocks at the same time. So, sometimes, we have to wait a little bit when we want to compare the interfaces.

Cédric noticed in the afternoon a bug in the IrDA functions and we fixed this. Now, the IrDA has more reliable and there are few problems in the network.

I still have problems when two networks meet with more than one block each involved in the « deal » but things are going better each day.

Benjamin worked on the launcher task. He thought of a remote block who can control the animation/game that will be played soon after.

Cédric continued the firmware transmission and the protocol is actually functional at good speed. But he is now facing problems with flash writing.

 

Here is a little video of the synchronization (running on the GLiPs but the MBLed are arriving soon):

 

Every block knows its i,j and minI, minJ, maxI, maxJ in the network. The block in the north-west shows a M; north-east a B; south-west LE: south-east D. If he is alone, he shows a M too.
That’s why sometimes in the video, there are 2 M : one of the block has encountered problems and reset himself.

For the synchronization, the leader gives the time every 20 PING (approximately every second), when a block receive that, it transmits it to his neighbor and so on.

 

 

TSV Safe Express: Sensors Card Development and Ethernet

Today, we received our 7 sensors card (which will track the position of the train and feed it to the central station), thanks to alexis who worked until very late in the night for soldering all the cards. So we wrote the code for the Sensor card which has a « producer » module who generates events on the CAN bus to indicate a sensor activity.

Also, Siwar is trying to do the communication protocol between ethernet and the server (setup by Samuel which controls the rail layout).

On the stabilisation of CAN, we are now filtering out events in CAN RX Queue 1(STM32 micro controller has 2 FIFIOs) and have left messages for network management on queue 0. This is done to avoid over-utilisation of queues due to either type of messages. Here is brief video of our project.

MB Led : Visual display of algorithm and snake first steps

Since our last post, Guillaume is still on the algorithm. Benjamin developed a display task for the old and new GLiPs. Now, we can see directly what’s going on in the network and try to debug it (see the picture). Yesterday, Guillaume tried to resolve bugs of freezing GLiP while the algorithm is running. He had to change many things in order to fix this and the only remaining freeze happens when some blocs leave the network.

There are some troubles when a block isn’t gone but don’t communicate with his neighbors. The biggest problem is when a block is rickety and that he communicates for time to time : he is considered as gone and soon after, he is here, etc. When this happens, the network can fail.

 

 

A little video to illustrate the visual debug:

 

Benjamin is develloping a special snake game concept for our system.

 

Guillaume and Benjamin.

 

IRL: the riddle with a mere oscilloscope!

Yesterday we achieved a new goal : we successfully played an ILDA animation on a mere oscilloscope. We attach a video as an evidence of our performance.

Let’s focus on what we actually did.
We built a program which plays directly an ILDA animation in the ILDA file format. We can set several options directly on the command line such as the time spent per frame and the scaling factor.

We enhanced our code which built an ILDA file from a string or a file. It operates directly on board and is now using an ILDA file per character instead of a SVG file with the whole charset.
We display directly on the board a list of tweets taken from a database and fetched them on the go with the twitter API that we now use in C instead of Python.

The IRL project would be nothing without those huge changes that drew our path since the beginning of the project. And we are proud to announce that we are changing (again) our architecture, and we would like to thank our teachers for their precise suggestions on that topic. In a word we are going to rely on a wishbone bus so as to assure the communication through the entities of the FPGA. In that way, out system will be cleaner plus it will enhance its capabilities.

RoseWheel: tests preparation

This week we tried to put together our developments and make them interact with each other. It includes sensors communication, kalman filter, control feedback, motors control, CAN communication protocol. We were dogged by bad luck as we realized the heatsink of our mainboard was too big to fit in the Zzaag… A few millimeters required us to order for a new one with a more suitable shape. Fortunately Alexis and Samuel helped us to find a new one. Because of that we were not able to validate the following « feedback control tuning » PSSC for Saturday as planned. Adviced by Samuel we also decided to postpone the « encoders drivers » PSSC as it wasn’t really in our first order priorities.

 

We tried to make profit of this situation and decided to prepare everything for the first tests. Alexis helped us defining our tests procedure to be as safe as possible for both hardware and people. Motors need special attention as they can be broken with unsuitable commands. Because of the wheels and the weight of the chassis they have a really high inertia. Asking them sharply to reverse their direction of rotation when they are rotating fast can seriously damage them and the H-bridges. If we damage them we wouldn’t be able to order new ones before the end of the course, it would be fatal for our project. Therefore we need at first to make some testing at low speed so as to define the maximum acceptable speed at which we can run the motors before they get damaged. To this extent we need an interpreter running on the mainboard and communicating using RS232 to be able to give motors various commands and define this maximum speed. Then we need to limit our commands to this maximum speed using software limitations. Finally the interpreter should be able to change the feedback control values for our testing to be more flexible. We implemented such an interpreter and made a video. The motors commands in the video are given between 0 and 1000 such as:

  • ml0 = 0%:  max negative speed
  • ml500 = 50%: stop
  • ml1000 = 100%: max positive speed

 

Before trying the Zzaag motors we do some testings on other DC motors with less inertia that we cannot damage as easily as the Zzaag’s ones. Putting all the pieces together we were able to shoot a video which shows the motors reacting appropriately to the inclination of the sensorboard. As for the Kalman filter, we implemented a lighter version than the one of RoseWheel as it works best when tested on the real system. This version was only able to track the gyroscope drift and correct it. As far as we could see during the testing, it did it well. Concerning the PID, we tried to test the version that we are going to use in the RoseWheel but it still needs to be improved during the next tests.

 

Tomorrow we will be able to work on the Zzaag motors using our safe procedure and the tools developped. We look forward to it as it is a major step further for our project…

TSV Safe Express: DCC Signals and Ethernet

Our journey has continued from CAN to LAN passing through DCC in its way. During the last two days, we tried to write the dcc encoder for our card which will act as the central station. In brief, I will try to explain DCC for all those who are not already aware of it. DCC (Digital Command Control) is a standard which permits us to operate model railways by sending modulated pulse wave(amplified with the help of a booster) to the rail tracks. Thereby, we can control any locomotive or accessory (like Traffic lights) if they have the dcc decoder. DCC is standard provided by NMRA.
We have done the following encodings for bit 0 and 1 as per NMRA DCC Standard.
(i) bit ’0′ – 232 microseconds (half high and half low)
(ii) bit ’1′ – 116 microseconds (half cycle is low)
On the implementation part, to generate such type of signal on the STM32 GPIO port, we use PWM module(using Internal Timer of STM32) with 50% duty cycle. This was setup in Output Compare Mode. Through the help of oscilloscope, we verified that we got the expected results. We created a dcc packet simulator(coded as a task of FreeRTOS) and we tried sending Messages to the port as per DCC Communication Packet format.

On the Ethernet part, we have chosen LwIP Stack as the TCP/IP Stack. We have chosen LwIP primarily as it has features like DHCP, UDP, IPv6 which we may need as the project matures further. So, we integrated the LwIP stack with STM32F107(which has in-built MAC Controller) and DP83848P Phy Controller taking help of a similar example provided by ST on their website. We were able to make a telnet connection to our Central Station and correponding exchange messages through telnet.

On the stabilisation of NMRA CAN protocol, we added a watchdog module within all the nodes including the central station. This was required because if the software hangs in one of the nodes, it should have the ability to re-join the network. The timeout of the watchdog module has been kept to 3 seconds(Typically because we want our nodes to rejoin the network as soon as possible and at the same time give Central Station enough time to remove this node from the node table and event table). Also, the command to reset the nodes sent by the network manager at the start of his execution as a broadcast message to all the nodes will have a deeper impact. Instead of doing a cache reset at the nodes, we are now doing an actual software reset to the node. This is just to simulate an actual reset. All these changes done to stabilisation are open for discussions and all remarks/critics/ideas are heartily welcomed.

Copterix: motors control, 1st test

Sensors and effectors

For now, we configured all sensors and effectors:

  • The Sharp, the distance sensor, works in 1-5m range and we get values with 3cm precision
  • Inertial Measurement Unit (gyros, accelerometers and magnetometers return correct values)
  • Radio Frequency (remote control, see video)
  • Motors (see video)

Here is a small video where we directly control motors’ speed with remote control:

Communication

We now have a reliable communication between our PCB and the Gumstix, thanks to Samuel Tardieu’s help.
We mostly use ZeroMQ to share data between our processes and even between our computers !

Kalman

Kalman is quite smoothly, works as well on PC as on Gumstix, and we are now optimizing each operation. The actual filter is fast enough for real-time execution (we spend a lot more time to wait after data than to actually process it), but we want the filter to use less processor working time in order to execute other heavy tasks, like Lucas and Kanade (video tracking algorithm).
We do now have a way to get by Wifi only the Kalman’s results in order to display them on a PC using OpenGL as you could have seen it on our previous videos.

Next step

We are now up to test for the first time real servomechanism PID on our Copterix !

Copterix : first moves

Yesterday we finally observed the first moves of our octocopter. After spending all the day working on the communication with the motors, Samuel and Axel have succeeded in controlling the motors from the STM32, with the help of Jon, passing by. They speak to them in I2C, and they can control the speed of the propellers. The Copter tried to run away, but he was fortunately attached on a table. However, we have to be more careful in the way we will attach it in the future, because it was close to a disaster.

On my side, I tried the RF controller, a Spektrum DX7 transmitter/receiver. I tested it on the STM32 board that we have previously use for the communication challenge, it works as we can expect, thanks to the code of the Heliokter team. We use indeed the code from last year’s project, which seems to fit to our needs. The RF receiver gives us access to different integers, which indicate us the pitch, the roll, the yaw and the thrust, and also some commands. The way the receiver communicates with the PCB is simple : it use the RS232 protocol, with a speed of 115200 kbps. It sends packets of 16 bytes separated by long period with idle line. I have implemented the code for our PCB and for getting the commands on the Gumstix, but I still need to test it.

On his side, Bertrand principally tried to debug some aspect of the STM32 code. When we send data in the both directions and look for the values of the sensors at the same time, some freezes occur. We think it’s maybe because the code needs some optimization, so Bertrand is working on it.