Hi everyone.

I'm looking for any assistance with a PerfectPrime TC0521 4-Ch Thermocouple Thermometer: https://perfectprime.com/products/tc0521

The datalogger has a USB port on it, and I would like to establish a serial connection with the datalogger from my PC. I would like to connect with it via serial using RS-232, with the provided serial protocol: https://cdn.shopify.com/s/files/1/1291/1589/files/TC0521_Protocol_1.pdf?v=1614323475 where the default baud is 9600 with an 8-N-1 protocol.

I have tried connecting the provided USB cable to the laptop and successfully run the datalogging program (called 521) that the manufacturer provides. Now I would like to connect to the datalogger via serial to integrate with another program.

When connected to my PC via USB cable, the Device Manager does not show an activated COM port. I have also tried to connect using:
Datalogger > USB Cable >USB to RS-232 adapter > Gender changer > USB to RS-232 adapter >PC. Although the COM Port appeared, I could not communicate with the datalogger. Likewise,
Datalogger > USB Cable >USB to RS-232 adapter > RS-232 null modem cable > USB to RS-232 adapter >PC also allowed the COM port to be exposed, but I couldn't communicate with the datalogger.

USB to RS-232 adapter: https://www.altronics.com.au/p/d2340b-usb-to-rs232-converter/
Gender changer: https://www.altronics.com.au/p/p1712-de9-female-to-de9-female-gender-changer/
Null modem: https://www.altronics.com.au/p/p1775a-de9-female-to-de9-female-null-2m/

Does anyone know what cable should be used in this application? Or perhaps what else I am doing incorrectly?

Thanks!

 

Unless the datalogger has a dedicated serial (RS-232) port in addition to USB, I don't think you'll be able to connect via a RS-232 serial connection.

The USB connection is NOT the same as a COM port. While there are many devices that implement what is called the USB Communications Device Class to appear to a PC as a virtual COM port, this will only work with a PC (or single board computer). You can never connect a USB to RS-232 adapter to a USB device, only a USB host such as a PC.

Since you stated this device does not enumerate as a COM port on your PC, it is more likely that this device uses the Vendor Specific Device Class, and therefore requires a USB driver installed on the PC.

Now, it does appear that the device you linked supports a bluetooth connection, which seems to support the Serial Port Profile, meaning it will appear as a COM port in your computer. I think this is the connection where the serial protocol applies. Therefore, you will need to establish a bluetooth connection between your PC and the datalogger in order to communicate using the serial protocol.

 

Thanks @jschulze, you've cleared up a bunch there.

Same problem, but on a different device. I have a vacuum pump that I would also like to connect via RS-232 to. Both sides have a USB-A port (pump & PC), but this time it comes with a picture from the manual.



I have already tried the following steps:
When connected to my PC via USB cable, the Device Manager does not show an activated COM port. I have also tried to connect using:
Pump > USB Cable >USB to RS-232 adapter > Gender changer > USB to RS-232 adapter >PC. Although the COM Port appeared, I could not communicate with the datalogger. Likewise,
Pump > USB Cable >USB to RS-232 adapter > RS-232 null modem cable > USB to RS-232 adapter >PC also allowed the COM port to be exposed, but I couldn't communicate with the datalogger.

USB to RS-232 adapter: https://www.altronics.com.au/p/d2340b-usb-to-rs232-converter/
Gender changer: https://www.altronics.com.au/p/p1712-de9-female-to-de9-female-gender-changer/
Null modem: https://www.altronics.com.au/p/p1775a-de9-female-to-de9-female-null-2m/

What cable should be used in this application? Or am I missing something else? Thanks!

 

A USB A port means the device is a USB host, just as a computer or single-board computer would be.

So for this application, you will need Qty.2 USB to RS-232 adapters (one connected to the vacuum pump and the other connected to your computer) and a null modem cable. You do not need, nor should you use, a gender changer.

Also, be aware that pump may not support just any USB to RS-232 adapter, since it will need to already have a driver for it built in. You may need to consult the documentation or contact the manufacturer to determine the supported chipsets used in the USB to RS-232 adapter (e.g. FTDI, Prolific, etc.). For example, according to the Windows driver files, the adapter you linked uses the PL2303 chipset from Prolific. If this adapter doesn't work with the pump, you may need to try an adapter with an FTDI chip in it instead.

Does the pump have any way of indicating that it has recognized a USB to RS-232 adapter being plugged in?

 

One additional thing to add. You can perform the following test to rule out an issue with your USB to RS-232 adapters or the null modem cable.

Connect both USB to RS-232 adapters to your computer (they should enumerate as separate COM ports) and connect them using the null modem cable. Use a terminal emulator, such as PuTTY, and start two instances - one connected to one of the COM ports and the other connected to the other COM Port. You should be able to type in one terminal window and see the text in the other terminal window.

 

Thanks for your help, jschulze. In the end, I needed a USB to RS-232 adapter with an FTDI chip before the cable was picked up by the pump.

I then connected a RS-232 null modem cable to another USB to RS-232 adapter, then to the PC, but this time the adapter had a Prolific chip.

I.e. Pump > USB to RS-232 adapter (FTDI) > null modem cable > USB to RS-232 adapter (Prolific) > PC.

I used the loopback test to ensure they were able to communicate, then connected the PC to the pump. The pump correctly responded when using PuTTY to the serial commands in the manual.

Thanks again.