Talk:Tasks:Can-Do Breadboarding
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Task specification vs. Task documentation
I'm not sure what the purpose with the recent changes of this task description has been. Was it intended to improve/expand the task specification or is it documentation of the work? In the first case, note that I have deliberately omitted too much details, since I'd like to define the exact scope of the work together with the people who are going to carry it out, in order to ensure that we have a well defined and limited scope that can be reached within short time. The same goes for the new diagram, which unfortunately causes more confusion than information. If the intention was to start documenting the work that is being done, that shall go on separate pages. In either case I would prefer to keep the task specification as simple as possible unless somebody takes it over. --Alexc 09:04, 16 January 2009 (EST)
Ok, I understand, agree with you. Ryan commissioning the work: perhaps the first thing you could do is create a diagram( you could just modify the diagram in the CanDo breadboarding task) which shows the different modules, sensors, etc.
I trying to understand system deeps base on a given diagram by Ryan. Please, feel free to correctme as much as need. I must learn a lot of thinks about the Lunar Lander which is my main task.
Perhaps he wants use the same diagram in other new task. Thanks again. --Joshua 22:31, 16 January 2009 (EST)
- Ok, sounds good. I just wasn't sure whether you wanted to document the work or to change the task specs. Anyway, I reverted the task spec to its original version and moved the documentation to a separate page: Can-Do Breadboarding. I think it will in general be a good idea to keep task specification and documentation separately. --Alexc 11:24, 17 January 2009 (EST)
Agree with you. Looks like better that way. Thanks. --Joshua 16:38, 17 January 2009 (EST)
BUS Components
What's the max possible datatransfer rate of a can-do bus? A high resolution cam as shown in the schematic needs "some" Mbit/s.
- This bus is intended for low rate telemetry and telecommand traffic (housekeeping data) in the order of kbps and not image or video transfer (payload data). However, even a camera unit needs commands ON/OFF/SET_MODE etc, which may come via this bus, of course depending on the design. As we discussed elsewhere, it is a very good idea to keep housekeeping and mission data on separate buses, if possible. --Alexc 04:48, 16 January 2009 (EST)
Well, I am in favor of simplicity. According to CAN BUS spececifications, bit rates up to 1 Mbit/s are possible at network lengths below 40 m. Decreasing the bit rate allows longer network distances (e.g. 125 kbit/s at 500 m). Separated buses may be justified with a good reason (perhaps I am ignorant of old decisions). In example, Ariane 5 (which uses MIL-STD-1553) have 2 redundant buses but all the information is carried by each bus. A third bus is dedicated separated from data bus. They uses a time distribution, having a large bandwidth for telemetry and reduced bandwidth for telecommanding. CAN-Do is not optimized for video streaming as you pointed and is not comparable with the 1553 bus (also 1 megabit per second). If we have enough bandwidth in a single bus, we can work together.
In the other hand, the CAN-Do in Standar Mode, the Module appears to an IHU as having 12 Digital output signal, 8 Digital Input Signals and 5 Analog Imputs plus Power Control current sensing and temperature sensing. In this configuration, an IHU can write 12 output bits and power control, read the eight input and the five Module defined and three dedicated analog input channels (10-bit precision). It should be able to do this with all the Modules on the CAN bus every 20 milliseconds.
Also, Multiplex Mode is available.
As far as I know, Lunar Lander is small. As less wires as we get less EMC problems (Electromagnetic Compatibility). --Joshua 23:17, 16 January 2009 (EST)
EMC
Is CAN bus electromagnetic compliance?
- Electromagnetic Interferences (EMI)
- Electromagnetic Environment
- Electromagnetic Emissions & Immunity
Joshua
- Good question, we'll have to take that into consideration. I'm wondering if it would mostly be of concern during launch or also during operations. We will most likely be powered OFF during launch. --Alexc 17:35, 13 January 2009 (EST)
I am worry for electrostatic discharges (ESD) in the system during operation. Since CAN Bus has an excellent error detection and confinement capabilities I am not worry for integrity during operation. ESD may damage componets. We don't have redundance so we may have special care about this topic during critical phases of the operation. I think redundance is not mandatory if we take protection against ESD. --Joshua 12:21, 14 January 2009 (EST)
Building a Test Harness
Alex, about the 'test harness' is this subtask a conceptual test or we may to implement the test it self?
If we may to implement one I may look for resources in order to buy 2 widgets and do the test.
I could buy as a part of my resource department. What do you think?
--Joshua 18:34, 15 January 2009 (EST)
- Yes, the idea was to set up a small test bench with a few simple microcontroller units connected via the CAN-Do interface. The MCUs would act as separate (dummy) instruments receiving telecommands and sending telemetry. Note, however, that I don't think you can buy assembled CAN-Do widgets or kits. I think we have to do that ourselves. --Alexc 09:04, 16 January 2009 (EST)
In all cases I must bay each components. This is not a problem because CAN-Do interface could be reused in my department. Regards. --Joshua 23:20, 16 January 2009 (EST)
Actual status
Could someone include me as an actual responsible of CAN-Do? I don't know how to change it. Thanks all. --Eric
- If you tell me who you are, yes ;-)
Just kidding... I have changed the contact person on Tasks:Can-Do_Breadboarding – I don't know if that's what you have had in mid? --Alexc 04:22, 26 August 2009 (EDT)
