  We report on the development, implementation, and characterization of digital
controllers for laser frequency stabilization as well as intensity
stabilization and control. Our design is based on the STEMlab (originally Red
Pitaya) platform. The presented analog hardware interfaces provide all
necessary functionalities for the designated applications and can be integrated
in standard 19-inch rack mount units. Printed circuit board layouts are made
available as an open-source project.\cite{APQGit_Lockbox,APQGit_IntStab} A
detailed characterization shows that the bandwidth 1.25 MHz and the noise
performance of the controllers are limited by the STEMlab system and not
affected by the supplementary hardware. Frequency stabilization of a diode
laser system resulting in a linewidth of 52(1) kHz (FWHM) is demonstrated.
Intensity control to the $10^{-3}$ level with sub-microsecond rise and fall
times based on an acousto-optic modulator as actuator is achieved.
