Hello, I am working on a project involving controlling a masterflex peristaltic pump (model# 7523-80). I am currently trying to use a usb to DB25 IO cable for the pumps 25pin IO port. Using the raspberry pi 4B I am trying to send commands (pulled from the pumps manual directly) but I cannot get anything to work. Is this even possible? Should I try connecting the GPIO pins directly to certain pins of the IO port? All I need to control is set the speed (ml/min), the direction, and be able to start and stop it.
So is the usb port on the I/O cable connected to a usb port on the RPi4b?
Does it show up in dmesg? Does it create a device file in /dev? Possibly /dev/ttyUSBx?
Do you believe you have the correct Rx/Tx correspondence between the cable and the pump? Based on what source of information?
Most serial line troubleshooting needs to start with a basic loopback test. Put a simple link or jumper between the Tx and Rx pins on the db25 cable. [Often that's pins #2 and #3, but check your documentation.] Use some tool of your choice - a terminal emulator or trivial script - to verify that test characters sent to the RPi serial Tx port are received and reported by the Rx port.
Regarding a direct connection. See the hazards highlighted in this recent discussion and associated documentation. viewtopic.php?t=373996#p2238428
A classic 'standard' rs232 serial signal is balanced or nrzi and has a signal level that can be negative with respect to ground. An RPi GPIO pin may not be able to deal with that signalling. That's partly why RPi recommend an external adapter such as you are using. [Although that cannot be taken as an endorsement for the anonymous/unspecified equipment you are working with.]
Statistics: Posted by B.Goode — Mon Jul 22, 2024 3:25 pm
