CANopen PDO mapping of data

Question

I am trying to perform a CANopen PDO mapping by only mapping the first two bytes of an unsigned32 data onto the PDO. Is it possible to do so and how?

I got the error code 0604 0041 (which means PDO cannot be mapped) for doing the above mapping.

Answer 1

First, check that the parameter is mappable. If you have the EDS file, the parameter of interest has PDOMapping=1.

If the parameter is mappable, you should be able set one of the mapping variables for the PDO to an encoded UNSIGNED32 Idx{16-bit}, Sidx{8-bit}, nbits{8-bit}. For example, if you wanted to encode 2000,05 as the first parameter of the first TPDO, set 1A00,01 to 0x20000510.

I forgot to ask:

1. Are you able to map the parameter in its entirety?
2. Have you made sure that the level of granularity your device supports for PDO mapping is bit, byte or word sized?
3. Are you trying to map the parameters while the system is in operational mode? Some systems do not support fully dynamic mapping. Some only support a static mapping, or mapping while in pre-operational mode.

If your system refused to map the PDO entry because the size did not match, I would expect the system to report error 0x06040042 (number/length of objects exceed PDO size) when setting subindex 0 at the end of the mapping procedure.

I believed it was possible to map smaller pieces of an object dictionary entry. I rechecked CiA-301, and it seems silent on the issue other than to say the length is mandatory.