Specifications

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Figure 2.4.1-1: Female USB
Type B connector. Reproduced
with permission granted by
sparkfun.com.
Figure 2.4.1-2: USB female Type A
connector pin arrangement. View is
directly into the mating opening of the
connector. Reproduced with permission
of sparkfun.com
2.4.2 Serial (RS232)
Another option would be to use a direct serial interface between the devices.
Many devices, especially more industrial electronic devices, often use a RS232-
compliant serial interface. It would also retain the advantages of the USB;
namely, a standardized interface with a standardized, easily obtainable cable. It
also offers a good amount of proven reliability for long term use. In addition, it
has the additional advantage of being able to be screwed in for a positive lock
from cable to device.
However, the connector (female connector shown in Figure 2.4.2-1) and cable
are not as compact as other connection methods, and if the user is intoxicated, it
can be difficult to secure the cable and screw in the securing screws to the
connector. This can create a situation where the connection may be severed
unexpectedly (since the DB9 connector has no self-locking ability), causing
errors between microcontrollers and frustrating the user. However, it is a
connection which would make connection to a technician’s computer easier, for
troubleshooting, updates, or reprogramming the unit for any reason.