As you build a modular system you will implement a lot of variables in each module that you might want to change as part of configuration or see as they are sensor values. To do this I create a separate module called a “Dictionary” that is illustrated below. The dictionary itself is a large Index…
I am waiting on parts for the USB, SD-Card, Ethernet and Modules so the next task I can work on is the CAN interface. The actual barebone CAN interface is autogenerated by STM32CubeIDE in C, so all we need to do is to create a proper IO queue, deal with timing and error handling. Most…
A PDO differ from a SDO in the sence that the COB ID is the message ID. In a single system you have 8 x 127 messages that can be PDO and only needs to be know by consumer and producer. A simple PDO Map can map directly to memory variables, but a more proper…
SDO is the simplest part of CANopen that can be compared to Modbus. A SDO message is addressed to a node and consist of Index, Sub-index and 1-4 byte variable. A common implementation is to have indexes in an array with pointers to the actual variable and use bsearch to find index/sub-index. How you implement…
I am considering using CANopenNode to create a full SIIS2 stack, but before I jump into someone elses work I like to think through how and why I want CANopen build. Below is a simple UML diagram. This diagram lack Bootloader and Object Dictionary, but I simply created classes for each bulk of work that…
The industry around me is a heavy user of CANopen (SIIS2) which is the “Subsea” version of a CAN protocol. CANopen is similar to Modbus, but it offer more functionality. It is also a more complicated protocol stack that tend to cost from 5-15K USD depending on content. I have written CANopen protocols in the…