More and more questions are currently being raised as to what the farm equipment of the future ought to be and how it should be designed to best meet contemporary challenges in farming. In Western countries, innovation in agricultural equipment is focused on a dominant model in which the agro-industry designs and patents standardised equipment for farmers. However, today's ambitions for agriculture, with agroecology in the lead, require us to devise farming systems that are adaptable to social and ecological uncertainties, and to recognise and embrace the diversity of situations in which farming is practiced. There has until now been little research on equipment design processes consistent with these principles, and this research helps to fill this gap. To address this issue, we studied the French "Atelier Paysan" R&D organisation, created to support on-farm design of suitable equipment for agroecology. Based on design theories, we analysed three aspects of Atelier Paysan's design activities: specific properties of the equipment designed under its aegis; specific features of the design processes; and roles that Atelier Paysan takes on to enable the design of this equipment. Our results show that all the equipment designed was appropriate for the designers' situations and requirements, and adaptable to other situations. It emerged from design processes in which the farmers had the support of R&D to design both their own equipment and the cropping systems for which it would be used. We call this the design of coupled innovations, and show that farm equipment and cropping systems are designed together during experiments. Lastly, we show that the Atelier Paysan R&D organisation supports these design processes in three ways: it enables farmers to share their experiences of on-farm design; it makes available a set of resources to stimulate farmer-driven design of new equipment; and it brings together designers scattered all over France around a shared ambition for agriculture. This work opens up avenues for research: (i) to explore an alternative to the dominant design, which would rely on coupled innovation design processes and allow for the emergence of appropriate and adaptable equipment that complies with agroecological principles; and (ii) to explore ways of organising open-innovation processes for agroecology, by supporting farmer-designers, and thus rethinking the roles of 'users' in these processes.