Classic Computer Magazine Archive COMPUTE! ISSUE 1 / FALL 1979 / PAGE 31


PETSET 1a $295.00

Connecticut Microcomputer, Inc.
150 Pocono Road
Brookfield, Connecticut 06804

Many PET users intend to do more with their computers than just play games. Small computers can do many (but not all) scientific calculations formally done on larger and more expensive computers. Laboratory data in analog form can be fed directly into a small computer using electronic circuits containing analog-to-digital converters. The result of an experiment can be known shortly after the experiment is completed and repeated if necessary. The equipment (PETSET 1A) reviewed here allows PET owners to connect analog data, from several instruments, directly into their PET. No special programming expertise is required of you and neither do you have to be an electronics wizard.

PETSET 1a consists of separate modules which when connected together, and to the PET, make up a 16 channel, 8 bit, analog-to-digital conversion system. I assembled this together in less than five minutes (I'm slow). Connections are made to a screw terminal barrier strip with just a screw driver. I believe the ease of installation will be attractive to potential users.

The software needed to use PETSET 1a is also quite simple: 10 POKE 59426,0: POKE 59426,255:? PEEK (59471)20 GOTO 10

The above program will sample analog channel 0 repeatedly, as fast as BASIC will allow. There is no need to check for end of conversion (EOC) as the conversion is completed (100 μsec) even before BASIC is ready to check. It should be easy to add statements which bring in data at specified time intervals using the real time clock. With more programming effort experienced users could write a machine language routine which would bring in data even faster than the simple BASIC program above.

PETSET 1a is connected to both the IEEE and User Port. It uses the IEEE port as a simple output control. For example, poking a zero to location 59426 starts conversion on analog channel 0. Digital data is brought in on the User Port by peeking at location 59471 (VIA output register without handshaking). The IEEE port can still be used for other devices such as CMC's printer adapter (ADA 1200) without disconnecting PETSET 1a. Technical specifications are:

16 analog inputs
100 μsec conversion time
0 to + 5 V inputs
0 to 255 counts (8 bit conversion)
input current, 2 μamp, max
max error, 0.5% typical

I was generally pleased with the system. However, the packaging is not as compact as I would wish. Some space is required behind the PET to accommodate the modules. A flat surface is also helpful. However, it does perform as advertised and is easy to put together and use. While it is not cheap, it is probably within many people's budgets. This system should definitely be considered if you:

  1. want to measure several voltages simultaneously,
  2. are satisfied with 8 bit resolution,
  3. don't want to spend lots of time with construction or programming.

Reviewed by Harvey B. Herman