Hi, I'm looking for a cheap micro with integrated CAN (optionally Transceiver ??). Wide area of supply voltage would be very welcome, of course. No special peripherals required, only some GPIO. The application doesn't need much of program or RAM memory. 1 K of Flash, some bytes of RAM, nothing more. Size matters. Because it should operate at a CAN speed of 250Kbit/s, a crystal is a must.
I would be glad getting any idea wher to look or ask.
Production volumes? I tried thinking of who to suggest, and I realized that CAN is getting pretty darn popular -- have you tried searching DigiKey's site using their excellent part finder?
NXP has some Cortex-M0 controllers with CAN and also with tranceiver option. They also include CANopen drivers in ROM, 16/32kB flash and
8kB RAM, so they are probably more than you need? LPC11C00 series.
--
Stef (remove caps, dashes and .invalid from e-mail address to reply by mail)
Experiments must be reproducible; they should all fail in the same way.
I don't think there are small and cheap microcontrollers with CAN,=20 because CAN requirements to software and hardware aren't small. The 1K=20 flash/some bytes of RAM is odd; the realistic numbers are 16K/1K or so.
ust.
Not really. CAN could cope with clock tolerances up to 1.5 percent.
The lowest cost microcontrollers with CAN are probably ST8 or HC08.
Vladimir Vassilevsky DSP and Mixed Signal Design Consultant
You are not going to get the CAN driver on a microcontroller - that will always be external.
I thought CAN can cope with bigger tolerances than that - it re-synchronises on bit edges, and bit stuffing ensures there are edges every 5 bits or so. But I don't remember the figures.
Also, the speed itself is irrelevant - it is the percentage tolerance that is important.
If all you're doing is a window roller-upper-downer or a tail light, the processor doesn't need to be very sophisticated. You may have more CAN than processor when you're done, though.
:))) What a naive idea. Especially as tail light is safety critical.
An automotive CAN stack takes about 8K of code and 1K of RAM at very=20 minimum. Plus RTOS. Plus system management. Plus diagnostic facility.=20 Plus bootloader. Somewhat 48K is required just to toggle a LED.
That would be really expensive.
Vladimir Vassilevsky DSP and Mixed Signal Design Consultant
Thanks for all replays I got. In the mean time I did also some research asking at distris. It seems that the NXP part LPC11C12FBD48 comes closest what I need. Because it has already the transceiver inside which also save aditional cents manufacturing costs. It's not an automotive product and will not need an RTOS, so it has much more memory recources than I need.
16 KiB Flash/8 KiB RAM. And much more pins than needed :-(
Regarding the oscillator tolerance. The not anymore valid Bosch CAn Spec
2.0 B says: "A maximum oscillator tolerance of 1.58% is given and therefore the use of a ceramic resonator at a bus speed of up to 125 Kbits/s as a rule of thumb;" The application needs to be stable in a wide temperature area.
I have seen some projects fail using the SiLabs Controller with internal resonator.
Regards Heinz
PS You might also check
formatting link
"3.2 Oscillator Tolerance Requirements" and the examples calculated.
If you try to implement CanOpen, DeviceNet or J1939, 16KiB/1KiB might be a bit on the low side.
However, if you have full control of the CAN ID assignment and the hardware has some CAN ID masking capability, 1 KiB flash and some bytes of RAM sounds quite reasonable.
Typo? The LPC11C12FBD48 does not have an internal tranceiver, for that you need the LPC11C22FBD48.
--
Stef (remove caps, dashes and .invalid from e-mail address to reply by mail)
You need tender loving care once a week - so that I can slap you into shape.
IIRC, the worst case is _ten_ bit times between syncs, and you need to keep the tolerance well below one bit time, especially if your sample point is late in the bit (e.g. 75% or even more).
Oliver
--
Oliver Betz, Munich
despammed.com is broken, use Reply-To:
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.