queryPump() doesn't work after pump has received a command

[dpk9]

After initializing pump, queryPump() returns [255, 47, 48, 96, 3, 13, 10]

After using the pump even one time, queryPump() returns None regardless of if the pump is currently executing or is still.

[dpk9]

Once a threaded function runs, the serial read port seems to be blocked from being read outside that thread (both the main thread or new threads). Examples:

• queryPump() works when first initialized.
• queryPump() works after running the non-threaded functions fillPump() or emptyPump().
• The first time a threaded function dispense() is called, the calls to queryPump() inside that thread still work.
• During dispense(), separate user-initiated queryPump() calls do not work.
• After the first time dispense() is called, queryPump() and any other functions that try to read serial data ever works again.

Look into "mutex"