■ PHOTO 3. A correctly aligned CP210x will
look like this with relation to the silkscreened
U1 part designator. Note D1’s odd and wider pin.
The correct orientation of the 4. 7 μF capacitor
(C1) is also visible in this shot.
■ PHOTO 2. What we want to
accomplish here is lay down just
enough solder to allow us to
bond the CP210x’s ground pad to
the printed circuit board pad by
heating the via. We also don’t
want to spill any solder paste over
into the pin area. Note the tiny
dab of solder paste in the upper
right corner of the ground pad.
marker is absent on the
CP2102, the CP2102
pin 1 orientation is
identical to that of the
CP2103. Correct pin 1
orientation for the CP2102 and CP2103 places the package pin 1 designator dot in the position shown in Photo 3.
Once you're sure about the CP210x's orientation, tack
down the part by soldering a couple of its opposing
corner pads. After you have secured it in position, heat
the ground pad via from the solder side just enough to
flow the solder paste you placed on the ground pad via.
If things go as planned, you will bond the solder plating
inside and around the ground pad via to the CP210x
ground pad. If you use an ExpressPCB PCB, the extra
solder plating on the pads will also reflow and provide
some additional solder for the joint. Once the CP210x
is solidly in place, you can carefully solder the rest of its
perimeter pads. If possible, use solder paste exclusively
as you can easily place a small dot of solder where you
want it with a toothpick or similar pointed instrument.
If you're using a soldering iron for assembly, here's
something to consider. To utilize the CP210x
parts, you only need to solder nine of the
CP2102's 28 pins and 14 of the CP2103's 28
pins. If you forego the LEDs in the CP2103
design, you only need to solder 10 of the
CP2103's 28 pins.
For those of you with hot air soldering
systems, you're in for a treat. The CP210x parts
just seem to grab the PCB pads and align
themselves when the solder goes molten. In
addition to the dot of solder on the ground
pad via, I coated the CP210x pads with a thin film of clear
solder paste before mounting and soldering with the hot
The PIC18LF4620 is a large target compared with
the CP210x and is easily soldered into place using a
hot air nozzle or a fine pitch soldering iron tip. The 0805-
packaged resistors and capacitors are also relatively large
components and are not at all difficult to mount and
solder down. The same goes for the 1206-packaged LEDs,
the SMT USB connector, and the crystal. If SMT soldering
is foreign to you, Robert L. Doerr's SMT soldering "How
To" in the January 2009 issue of Nuts & Volts is a good
reference for those of you tackling SMT soldering for the
In the midst of celebrating your soldering success with
the CP210x and the PIC18LF4620, be sure to solder the
USB connector shell tabs to their grounding pads. The
SUSPEND, VBUS, VIO, and VDD termination points are
intended to allow you to electrically mix these signals and
voltages into circuitry you assemble in the breadboard
area. If you decide to use the VIO feature, be sure to
cut the solder side trace between the VDD and VIO
■ PHOTO 4. After designing the CP2103 board, I felt that
I had to cover all of the CP210x bases and put this one
together, as well. If you only need to replace an existing
RS-232 interface with a USB connection, build this one up.
■ PHOTO 5. Everything you need in a USB-to-UART Bridge
is here. If you need additional I/O, Dynamic Suspend, and
RS-485 support, build this one up.