pimp my VC96(Voltcraft)_en

Hi to all,

since it was more and more annoying to connect my VC96 to the laptop 
using a separate RS232-USB apapter I modified my modification from many 
years ago.

I used a tiny cheap RS232-TTL-USB adapter modul and a LM2904 opamp on a 
universal stripe pcb.

The signal conditioner is powered by the 5V coming from the USB modul. 
It supplies the photodiode SFH205. Those fits into the window towards 
the VC96 in the apapter case. The first part of the opamp U1A amplifies 
the signal from the photodiode about 50 times, the second part U1B is a 
comparator. It triggers the signal from the amplifier against a average 
value built by the low-pass consisting out of R3 and C2. This average 
value makes the signal free of influence of i.e. sunlight. The 
conditioned signal goes into RXI> of the RS232-TTL-USB adapter modul 
connected by a micro USB cable.

I also made a driver for Sigrok and Uwe Hermann has it already 
integrated into Sigrok.
https://sigrok.org/wiki/Voltcraft_VC-96

Matthias