Project for connecting analogue signal to serial port. Included Visual Basic VB6 software and a circuit diagram. The MCP3201 is a micro-power 12 bit analogue to digital converter. The conversion selector reads all the 12 bits, the 10 or 8 MSB and ignores the LSB. With less resolution the reading is more stable. The supply to the circuit is via the 12V at pin 7 that are switched to logic high by the software.
The communication to the PC is bit banging the Hardware Controls, the DTR is used for clocking the ADC and the CTS is used for data input.
You can read more about serial interface in http://www.beyondlogic.org/spp/serial.htm
Datasheet for the MCP3201 can be downloaded from here. LTC1285, ADS7822 are direct replacement to MCP3201.
You are free to use the circuit diagram and VB code with no limitations.

MCP3201
Input at pin 2 of the ADC is 0 to 5 volts full range positive voltage only. The chip over voltage protection is 5V max.
Pin 8 is the 5 V supply to the IC.
Pin 1 is reference voltage for the ADC , it's connected to the 5V and can be connected to an external reference voltage. The reference voltage determents the input voltage span.
Pin 6 is the serial data out of the ADC, BC237 and BC327 are a level shift from 0-5V to -8 to +8V which is the voltage required for the serial connector.
Pin 7 is the clock for reading the data and pin 5 is the Chip Select. The 22K resistors are for lowering the 12V out of the serial port to 5V level of the ADC.

roject for connecting analogue signal to PC without a need for microcontroller. Included Visual Basic VB6 software and app, VS2010 code and circuit diagram. The MCP3201 is a micro-power 12 bit analogue to digital converter. The conversion selector reads eigther 10 or 12 bits. With less resolution the reading is more stable. The 5V supply to the circuit is from the USB.
The communication to the PC is bit banging the Hardware Controls, the DTR is used for clocking the ADC, RTS as CS and the CTS is used for data input.
Datasheet for the MCP3201 can be downloaded from here. LTC1285, ADS7822 are direct replacement to MCP3201.
The USB to Serial I used is: https://www.ebay.co.uk/itm/CP2102-USB-2-0-to-TTL-UART-Module-6Pin-Serial-Converter-STC-Replace-FT232-Module/381374541932?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649
There are other similar modules, make sure they have all the connections needed. RTS and CTS need to be soldered, they come with only holes in the module's PCB.

Using USB to serial module drive 2 outputs that can be LEDs or relays. Also read 2 digital inputs from a switch or a DC source. The app uses the Hardware Controls of the USB to Serial module; inputs CTS, DSR and outputs DTR, RTS. Outputs and inputs are 3.3V , to sense voltage over 3.3V it's needed to add a series resistor to the module input.
The app is in VS2010. In the app enter the Com Port that the USB to Serial modules opens. 2 LED images show the state of the 2 inputs and 2 tickboxes operate the 2 outputs.
The USB to Serial I used is: https://www.ebay.co.uk/itm/CP2102-USB-2-0-to-TTL-UART-Module-6Pin-Serial-Converter-STC-Replace-FT232-Module/381374541932?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649
There are other similar modules, make sure they have all the connections needed. RTS and CTS need to be soldered, they come with only holes in the module's PCB.

You are free to use the circuit diagram and the VB software with no limitations.