I am recently moving from C programming into automation engineering. I have learned about RS232 and TTL standards, and I understand that they are based on the same concept of serial communication, however TTL uses logic voltages (3.3 V or 5.0 V) to be compatible with microcontrollers, while RS232 uses higher voltages for historic reasons (signal-to-noise-enhancement).
To start connecting to the "real world", I planned on using a simple printer to start practicing sending bits via the COM-Port. Here is a link to an example: https://de.aliexpress.com/item/JP-QR203-58mm-Micro-Receipt-Thermal-Printer-RS232-TTL-USB-Panel-Compatible-with-EML203/32693670343.html
This device seems suitable for my needs, however, some questions remain, as I am very eager to learn, but still a newbie in electrical engineering:
The interface is stated as "Serial (RS-232,TTL)" - Is there any way to find out which standard is implemented on the PCB exactly, RS232 or TTL?
Another suitable device seems to be this one here: https://www.amazon.de/WELQUIC-Thermodrucker-Bondrucker-Bluetooth-Standard-Art-1/dp/B075GG7VJT/ref=sr_1_2?ie=UTF8&qid=1533543476&sr=8-2&keywords=welquic+printer
Again, how can I figure out whether RS232 or TTL is implemented?
This device seems to feature a Mini-USB port for USB-communication and another Mini-USB port for RS-232/TTL communication... Which cables would be needed? Is there something like a serial/Mini-USB adapter cable? As I understand, USB standard has to be converted to RS232 or TTL - So my second question basically is, how can there be a port in Mini-USB-format for RS232/TTL?