Developer notes to evaluate http://caraca.sourceforge.net/
We don't want to duplicate their docs, but evaluate how it competes with HW implemented CAN (in LPC ARM) or modbus over serial (or profibus or similar).
I know some people (Johan?) examined closely, please take some notes.
Main questions:
- how easy it is to integrate to our firmware? if costly, we might just want to drop ARM on every network-designated board and postpone CAN support for small uC-s
- interrupt latency it introduces (important if the main task of uC is ignition control)
- CPU clocks from userspace (not as costly as CPU clocks spent in interrupt, but still counts) for given baudrate. This changes in function of:
- minimal: if all frames are neglected (addressed to other nodes)
- if all frames are fully processed
CPU overhead
- Using HW uart (right?) so: 1 interrupt / byte on AVR (no FIFO)
- I assume bytes (at least for non-neglected frames) are immediately passed up to userspace, so interrupt handler is short (right?)
- CRC calculation? Costlier (regarding CPU and flash) than modbus.org (modbus over serial) RTU checksum?
- other costs ? bit stuffing or similar ?