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I have been assigned to a project to find the best possible communication between several PCB boards which have microcontrollers for a specific function. I need to have all microcontrollers communicate with the main board which contains a CPU.

I need to send some information from the mainboard to the controllers and receive a response from the controllers. Each controller board is designed for a specific purpose. I don't need to communicate between the microcontrollers, but even if one microcontroller fails to communicate then it won't effect on others. Presently, I need to have six microcontrollers communicate, but in the future more than that. I want to avoid more wired connections between the mainboard and the other controllers (it should be fewer).

The communication should not be affected by the temperature (250 °F (120 °C)) and pressure (high). The distance between the mainboard to the final controller may be more than one meter. Which type of controllers are best? I need to perform some calculations and sensor readings. Each board having more than two sensors. I need to perform some calculations on sensor readings or send values directly.

I am new to this type of project. I have searched for the best communication, but I am confusing which is best. Some people are suggesting me to use CAN communication. If I choose CAN communication, what type of microcontrollers is best? I have attached a simple diagram how it is going to look like as shown below.

Design

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  • \$\begingroup\$ Can you confirm that the temperature seen by a micro is expected to be 180ºC? \$\endgroup\$ – Andy aka May 2 '13 at 14:15
  • \$\begingroup\$ @Andyaka I am sorry, the temperature range is about 100 to 120 degree. Is there any atmel controller which have CAN built in? \$\endgroup\$ – verendra May 2 '13 at 14:34
  • \$\begingroup\$ Have you checked with Atmel? If you have then there's no point me doing it. If you haven't, why not? I've used PICs on two recent jobs at 120ºC when they were specified at 85ºC - both jobs work and continue to work but you'll probably not get any confirmation of that from any supplier because why should they do special tests for you or anyone with low quanitity requirements. \$\endgroup\$ – Andy aka May 2 '13 at 14:41
  • \$\begingroup\$ CAN sounds like a good fit, except that you haven't told us the bandwidth, so we can't tell. At a meter or a few meters, you can run CAN at 1 Mbit/s. Many micros come with CAN built in. For example, I have used the PIC 18F25K80 quite a bit for this sort of application, but there are many others both within the PIC line and from other manufacturers. You may have to get extended temperature range parts, but covering 82 degC won't be a problem. \$\endgroup\$ – Olin Lathrop May 3 '13 at 19:26
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    \$\begingroup\$ One thing you're going to need to be aware of is you will not be able to use a significant number of common passive components. At 82°C, electrolytic caps are pretty much a non-option. You're going to have to be all tantalum. Also, many ceramic cap dielectrics are out. A Z5U ceramic cap will have deviated pretty far from it's rated value at that point. Basically, you're going to need parts that are specified and rated for those temperatures, and to ensure that the value changes caused by the high temperature won't negatively effect your system behaviour. \$\endgroup\$ – Connor Wolf May 3 '13 at 21:05
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If you choose CAN then the "best" micro is one with CAN built in (many have this, Coldfire MCF5225x is one example).

I2C or RS485/RS422 are good choices too, depending on the electrical characteristics of the situation (distance, noise, power). The rest comes down to the protocol you use for communicating - how to address messages, control flow, avoid collisions.

I'll wish you good luck finding a micro which will work at 180c, automotive spec tops out at 125c and I don't think even military spec improves drastically on that.

You need to start with layer 1 (electrical) to work out what the physical interface has to do, after that it's mostly a software issue on how you talk. These days, ethernet might even be a viable option if the micros have the space to run a modest OS.

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  • \$\begingroup\$ Sorry for the misunderstanding the temperature range is about 100 to 120. Is there any atmel controllers which have CAN built in? \$\endgroup\$ – verendra May 2 '13 at 14:33
  • \$\begingroup\$ @verendra atmel.com/products/automotive/default.aspx I think their automotive processors likely have CAN. I use PICs myself. \$\endgroup\$ – kenny May 2 '13 at 15:20
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    \$\begingroup\$ @verendra - For the love of zog, ALWAYS include the unit when describing temperature. 120°C is VERY different then °F. \$\endgroup\$ – Connor Wolf May 3 '13 at 21:07
  • \$\begingroup\$ @ConnorWolf I am very sorry for the mistake i have done here. I am trying to find components which sustain at 120ºC. \$\endgroup\$ – verendra May 6 '13 at 6:54
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    \$\begingroup\$ You need to think about the temperatures - is it 120C ambient air temperature, 120C inside the box, 120C on the micro itself? Is there cooling? Fans? Heat-sinks? Peltiers? Can you move the micro further from the heat (put the sensor on a longer wire) to reduce the heat? 120C is not as much of a problem as the thermal cycling if the unit is regularly cycled between 120C and, say, 10-20C ambient, the expansion/contraction will fracture solder joints etc. \$\endgroup\$ – John U May 7 '13 at 9:51
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You can take a look at http://www.keil.com/dd/chip/3648.htm LPC 2129 ARM7TDMI-S with CAN support. This can help if you fix your interface as CAN. You can also have Industrial or MIL grade connectors and cables because of your temperature constraint. Check out vendors like Radiant cables, TE connectivity, Amphenol, Allied Connectors which manufacture stuff meant for high temperature environment. Also, you can check out some heat resistant materials such as teflon that help protect the communication interface.

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    \$\begingroup\$ Welcome to the Electrical Engineering Stack Exchange! There are a number of processors with CAN support...why did you suggest this one? Is it specified for operation at 120C? If so, include those details in your answer. If not, then you haven't helped the OP. \$\endgroup\$ – Joe Hass Nov 21 '13 at 11:56
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For CAN (and I would strongly advice CAN for your setup) I recommend the LPC11C24, an ARM Cortex-M0. I think it is the only one that has the transceiver already incorporated, so there is no need for an extra chip to implement the physical layer (as is usual in the rest of CAN microcontrollers). It also has some nice and easy to use C libraries built-in in ROM for CAN and CANOpen standard.

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Freescale S08D family or some cheap Kinetis has CAN and support to 125ºC. However highest values of temperature you get only on valuable chips on Freescale (source: parametric search). Try Parametric Search of all sites!

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  • \$\begingroup\$ Most devices from most manufacturers are available in automotive-grade or military-grade with the 125ºC rating, this info doesn't seem particularly special? \$\endgroup\$ – John U Jan 30 '14 at 19:54
  • \$\begingroup\$ Although I have found high values​​. I have not mentioned because the question establish only 120 degrees and appear to demand cheap uCs. But my answer was not very helpful indeed. \$\endgroup\$ – user19978 Jan 30 '14 at 20:04
  • \$\begingroup\$ TI has few products that are meant for 150C ti.com/product/msp430f2619s-ht \$\endgroup\$ – Lior Bilia Jan 30 '14 at 20:11
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CAN is pretty complicated in implementation in software.

Why not to use RS-485 which is also industrial standard? There are many RS-485 transceivers with 125'C temperature support.

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