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CANopen shell commands
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Show status report:
  copen status

Start / stop workers:
  copen <bus> start
  copen <bus> stop
  - stop will fail if clients are still running.

Send NMT commands:
  copen <bus> nmt <start|stop|preop|reset|commreset> [id=0] [timeout_ms=0]
  - id 0 = broadcast
  - timeout > 0: wait for state change (heartbeat), 3 tries
    Note: state change response is not a mandatory CANopen feature.

Read SDO:
  copen <bus> readsdo <id> <index_hex> <subindex_hex> [timeout_ms=50]
  - index & subindex: hexadecimal without "0x" or "h"
  - defaults to 3 tries on timeout

Write SDO:
  copen <bus> writesdo <id> <index_hex> <subindex_hex> <value> [timeout_ms=50]
  - index & subindex: hexadecimal without "0x" or "h"
  - value: prefix "0x" = hex, else decimal, string if no decimal
  - defaults to 3 tries on timeout

Show node core attributes:
  copen <bus> info <id> [timeout_ms=50]
  - prints device type, error register, device name etc.
    Note: some attributes read are optional and may be empty/zero.

Scan bus for nodes:
  copen <bus> scan [[startid=1][-][endid=127]] [timeout_ms=50]
  - loops "info" over multiple node ids (default: all)
    Note: a full scan with default timeout takes ~20 seconds