pH- doser bricks arduino

[jakerye]

• When trying to set the ph to 3 with the current solution at 4, the arduino bricks.
• Started debugging via python serial and arduino only. See https://wiki.openag.media.mit.edu/users/rbaynes/notes/python#serial.
• Noticed that if the ph- pump receives a True command every 1 sec, the arduino bricks. However if it receives a True command every 2 or more seconds, the arduino does not brick and behaves as expected.
• Tried this same test on the ph+ pump, but arduino did not brick when sending a command every second. Even functioned properly when sending commands once every 0.5 sec.