MicroFPGA

Logo

An affordable and open-source FPGA platform for the electronic control of microscope.

View My GitHub Profile

Electronics

The electronics is available in the MicroFPGA-electronics repository. Since the project was updated, the most complete guide about the electronics is in the published paper.

Here we only describe small use cases involving the following boards:

Signal conversion board

SCB

Channels

The signal conversion board is composed of 8 channels:

The channels only differ by the analog detour option. For the conversion channels without analog detour, or when the analog detour is ignored, the channels can be used in either direction: voltage A -> voltage B or B -> A. When the analog detour is soldered in, the voltage conversion is only performed A -> B. The low pass step is performed by a Sallen-Key circuit with a cut-off at 10 Hz.

In order to choose the input and output voltages, refer to the channel header:

Signal conversion board

The channel header allows choosing the following parameters:

Use cases

Analog conversion board

ACB

Channels

Since the Au FPGA analog input are limited to the 0-1 V range and are only safe up to 1.6 V, an additional circuit is necessary to convert commonly encountered 5 and 10 V inputs. The analog conversion board is composed of 8 channels allowing 1/10 or 1/5 voltage conversion. Additionally, the voltage and current limit can be disabled.

Signal conversion board

Each channel header present options that need to be jumped:

Use case

If a sensor on the microscope has an analog output comprised between 0 and 10 V, feeding it directly to the Au FPGA will saturate the read-out channel. Therefore, the signal is set as input of the conversion board, with the 1/10 option selected as well as the “voltage and current limitation” one. The output of the channel is then safe to be wired to the FPGA and the will allow reading out the signal.

Examples of applications are for instance monitoring the laser power meters or the focus of the microscope.

AOTF conversion boards

(soon)

Channels

(soon)

Use case

The AOTF-CB allows generating an analog output synchronized with the camera (in active or passive sync). It is best used with a PWM channel for the output level, and a laser trigger signal as synchronizing TTL input.

The main use case is setting laser power through an AOTF, thus allowing the laser to be synchronized with the camera, especially when direct TTL triggering is not available (e.g. DPSS lasers).

Alternatively, a faster PWM and a modified AOTF-CB (see tutorials), could allow fast synchronization compatible with galvo-mirrors for instance.