Got PWM? Pulse Width Modulation is very useful when programming microcontrollers. You can use PWM to control motor speed, LED brightness, or even generate an analog voltage by filtering the pulse train with an RC network. If you've used software PWM (like the PWM command the Basic Stamp provides) you may have been disappointed. Most software PWM solutions only generate pulses while you aren't doing anything else. Also, many software PWM engines (including the Stamp) don't use a constant pulse width. For example, 50% duty cycle might be 10uS on and 10uS off. But 1% duty cycle might be 10uS on and 246uS off. This can lead to motor noise and other undesirable effects.

The PAK-V offers 8 simultaneous PWM outputs with no overhead from the host computer. You simply send commands via ordinary RS232 protocol and the PAK-V generates PWM until you tell it to stop. You can select 9600 or 2400 baud and use true or inverted serial logic. A simple command switches the PWM generation from proportional (like the Stamp) to equal-area PWM.

The PAK-Vc is backward compatible with the PAK-Vb, but adds a special mode that allows you to connect 2 to 32 PAK-Vbs to a single pin! That means you can control up to 256 outputs from a single RS232 output.

Perfect for robotics project, motion controllers, or anywhere you need to generate analog voltages with 8-bit resolution. These chips are also very popular in lighting applications since they can dim an LED or other light source (with appropriate drivers, of course).

Features include:

• Serial interface uses TTL-level RS232 at 9600 or 2400 baud (true or inverted)
• Uses as little as 1 pin to connect to the host microprocessor
• Enable pin allows you to use multiple PAKs with the same I/O pin (requires 1 enable pin per device)
• Stamp users can use SEROUT to send commands
• Commands include: DUTY, RESET, PROP (proportional mode), and EQUAL (equal-area mode)
• Select proportional mode (like the Stamp, approximately 2uS time slice) or equal area PWM (duty cycle of a 512uS period)
• Includes 50MHz ceramic resonator

The Details

With the PAK V you'll receive the IC, a ceramic resonator, and a data sheet. The data sheet explains the commands you can use and how to interface the IC to any microprocessor that can send serial data.

The new PAK-Vc is a 28 pin device and can be clocked to 75MHz to provide faster PWM pulses if desired.

What to use a PAK-V on the PC? It's easy. Find out how.

View the PAK-Vb/c data sheet online.

Consider this simple Stamp program:

' Example PAK-V Program
DataPin con 0
EnPin con 1

' Enable=High / Disable=Low
HIGH EnPin
i var byte
br var word
inv var word

br=84  ' 84=9600 396=2400
inv = 000 ' $4000 is inverted, 0 is normal
' Select Mode
serout DataPin,br+inv,[$85,$83]  ' $81=eqarea $83=proportional
top:
' 1st go from 0% to 100%
for i=0 to 255
serout DataPin,br+inv,[$27,i]
pause 10
next 
' Next go from 100% to 0%
for i=255 to 0
serout DataPin,br+inv,[$27,i]
pause 10
next 

goto top

What's the output look like? Take a look at these oscilloscope movies (in MPEG format):



[Equal Area (MPEG 758KBytes)]



[Proportional (MPEG 466KByte)]

Get it Now!

Try a PAK-V for 21 days. If you aren't delighted, just send it back undamaged for a full refund of your purchase price. But once you see your Stamp handling PWM like a champ, you won't want to be without it.

Need volume pricing?

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Add to Cart PAK-Vc Coprocessor $24.95 each (28 pin). Recommended for new designs

Add to Cart PAK-Vb Coprocessor $24.95 each (28 pin). Not Recommended for new designs

Notice: Basic Stamps are a product of Parallax Inc. AWC is in no way affiliated with Parallax.