As part of an ISOBUS system, the communication library ISOAgLib developed by The ISOBUS Experts guarantees all functions which, in accordance with the ISO 11783 standard, are available or may be present in an electronic data communication system. These functions include, for example, the display of user interfaces on a virtual terminal (VT) or task management on the basis of process data in the task controller (TC).
All functions and machine-specific interfaces defined in the ISO 11783 standard are already implemented, ensuring that entry into the ISOBUS world is particularly simple.
Another advantage of the ISOBUS Stack is that this software solution functions entirely independently of the hardware.
The ISOBUS Experts have developed the ISOAgLib Safety Edition (SE) from scratch in 2017. This version meets the current standards for functional safety and is therefore "Safety ready". The implementation was carried out in compliance with SRL-2 according to ISO standard 25119 and is certified annually by TÜV Süd.
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|---|---|
| Implementation of the ISO 11783/ISOBUS standard | |
| Commercial license, including updates to the latest version of the ISO 11783 standard and general ISOBUS support | |
| Guaranteed AEF ISOBUS certification | |
| Quality assurance through reviews | |
| Quality assurance through automated module and iteration tests; manual system tests for validation | |
| Developed under strict observance of the ISO 25119 standard for functional safety | |
| No dynamic HEAP necessary; use of static RAM (buffers are configurable) only | |
| Compile-capable with all C99 (and most C90) compilers | |
| Optimum memory usage for the VT client “object pool” |
To guarantee the functional safety of safety-critical software in running operation, the ISO 25119 standard has defined various Software Requirement Levels (SRL). As the demands placed on system safety increase, so too do the requirements with respect to planning, development and maintenance of the relevant software.
In addition to the ISO standard, the AEF regularly issues updated guidelines with recommendations on implementing and interpreting standards. For safety-relevant systems in agricultural engineering, the AEF recommends implementation according to SRL 1. Nevertheless, we have opted for the development of ISOAgLib SE for SRL 2. The differences between SRL 1 and SRL 2 with respect to planning, development and maintenance may be seen in the table below.
| Required methods regarding the software requirements level | SRL 1 | SRL 2 |
|---|---|---|
| General | ||
| AgPL Coverage | Total coverage of AgPL=a and only partly coverage of AgPL=b and c | Total coverage up to AGPL=d |
| Corresponding SIL | Max. SIL 1* | SIL 2* |
| Software safety requirements specification | ||
| Requirements specification in natural language | ||
| Description of software safety requirements with semi-formal and formal design methods | ||
| Usage of computer aided specification tools | ||
| Inspection of software safety requirements | ||
| Software architecture and design | ||
| Use of trusted/verified software modules and components to avoid the need for extensive revalidation or redesign for each new application | ||
| Semi-formal and formal design methods | ||
| Structured programming | ||
| Use of coding standards | ||
| Inspection of software design and/or source code | ||
| Software module testing | ||
| Boundary value analysis | ||
| Control flow analysis (detecting poor and potentially incorrect program structures e.g. inaccessible code, knotted code) | ||
| Data flow analysis (detecting poor and potentially incorrect program structures e.g. read variables before value was assigned, written but not read variables) | ||
| Walk-through/design reviews (detect faults as soon as possible during development) | ||
| Equivalence classes and input partition testing | ||
| Integration testing | ||
| Functional and black-box testing | ||
| Performance testing regarding response timings and memory constraints | ||
| Performance testing regarding performance requirements | ||
| Software safety validation | ||
| Test interface | ||
| Tests within the ECU network | ||
| Hardware-in-the-loop tests | ||
| Additional feature | ||
| Comprehensive System Validation Test** | ||
„Why do our customers opt for ISOAgLib SE? Decisive for our customers is the implementation of ISOAgLib SE according to the SRL 2 requirements in compliance with ISO 25119. Current AEF guidelines only take into account application scenarios which meet AgPL=C and thus recommend implementation using SRL 1 only. In this way, we are offering our customers the highest possible degree of investment security around on the market to day. With the increasing degree of automation, the requirements placed on the functional safety of a system are also rising. With ISOAgLib SE, our customers are opting for a future-proof and long-lasting technology. Another reason is the consistently high quality of the software, which is guaranteed through the numerous tests and checks carried out according to SRL 2 during implementation.”
Martin Wodok
Manager Research & Development The ISOBUS Experts