The low energy X-rays of the pionic deuterium 3 P-1 S transition were measured using a high resolution crystal spectrometer, together with a cyclotron trap (a magnetic device to increase the pion stopping density) and a CCD (charge-coupled device) detector system. The spectrometer resolution was 0.65 eV FWHM for a measured energy of approximately 3075 eV. This energy was measured with a precision of 0.1 eV. Compared to conventional methods, the cyclotron trap allowed for a gain in stopping density of about an order of magnitude. The CCDs had excellent spatial and energy resolutions. Non-X-ray background could therefore be almost completely eliminated. The 1 S strong interaction shift ϵ 1 S and total decay width Γ 1 S were determined from the position and line shape of the X-ray peak. They are ϵ 1S( shift) = 2.43 ± 0.10 eV ( repulsive), Γ 1S( width) = 1.02 ± 0.21 eV , where the statistical and systematic errors were added linearly. The total (complex) pionic deuterium S-wave scattering length a π − d was deduced: a π −d = −0.0259(±0.0011) + i0.0054(±0.0011)m π −1 . From the real part of a π − d a constraint in terms of the isoscalar and isovector πN′ scattering lengths b 0 and b 1 was deduced. From Im a π − d we determined the isoscalar coupling constant for π − absorption: | g 0| = (2.6 ± 0.3) 10 −2 m π −2. The experiments of the pionic hydrogen and deuterium S-wave scattering lengths were analyzed within the framework of a search for i isospin symmetry violation. The data are still compatible with isospin conservation. The scattering lengths deduced from the Karlsruhe-Helsinki phase shift analysis disagree with the present results.