CAI Instrument's Widget Board Price: $79.95 CAI Instruments, 2559 Arbutus Ct., Midland, MI, 48640, 517/835-6145
Most of us are pretty tired of waiting up to a year for delivery and then getting equipment and manuals with obvious mistakes. Couple that with an unresponsive manufacturer and you get frustrated customers. Because of problems detailed below, SYNTAX recommends that you delay purchasing the Widget until CAI Instruments offers correct, complete, and consistent documentation and prompt shipping schedules. If you can deal with these problems yourself, the Widget provides you with a packaged set of ports and peripheral controllers.
You pay more for the Widget without printer and tape control EPROMS–$80 for the Widget alone, only $60 with printer and tape drive. ROMs come with the peripheral, not with the Widget.
The Widget plugs into the ZX80/81 expansion port. The 16K RAM plugs into a similar port at the rear of the Widget. At the left of the Widget housing you see three connectors–two IC sockets to connect CAI’s printer and continuous tape drive plus a 20-pin male connector for parallel and serial port outputs.
You MUST add RAM to use the Widget, and all 16K machines we tried appeared to have only 2K remaining with our Widget attached. CAI Instruments say that they use the upper 4K of memory, leaving 12K free with a 16K RAM. We are unable to verify that.
CAI’s device produces RS-232C compatible serial output. That means the electrical signals provide well-defined voltages and signal timing. It does NOT mean that all RS-232 control functions or ASCII translations are provided. Nor do you get a standard RS-232 connector.
We judge the pinout, diagrammed below, to sensibly segregate the serial and parallel ports as well as the parallel input and output. To use ribbon cable, you’ll have to unscramble things at your end.
RCV D4 D2 D0 D6 D3 D5 D2 D1 o o o o o o o o o o SER OV INPUT DATA OUTPUT DATA o o o o o o o o o o XMT D7 D3 D1 D5 D4 D0 D7 D6
The bare-bones Widget gives you a fully-buffered expansion port, but no hint of how many loads you can drive. You also get two 8-bit, parallel ports, one input and one output. Third, you get serial I/O with RS-232 signal levels at one, jumper-selected, Baud rate of 300, 1200, 2400, 4800, or 9600.
In my judgement, Widget construction techniques may induce failures and make maintenance tough. Inside, 39 separate pins connect the 2 stacked boards electrically and mechanically–a maintenance nightmare.
Half the ICs are sandwiched between these boards, a problem for both cooling and maintenance. Our sample contains 4 unrestrained long wire jumpers (1 soldered directly to IC pins at the device bodies) –expect trouble here from vibration. When attached, the Sinclair RAM hangs unsupported on its connector.
The instruction manual contains inconsistencies in POKE or PEEK addresses and programs that will not run. Modifications listed for the 8K ROM are correct, but not complete. Devise your own scheme to check the status bit on 8K machines because CAI’s example ignores 4K/8K ROM differences. CAI provides a schematic with the Widget and hardware buffs could fill in the omissions. Computer and I/O busses are shown in single-line form with complete pin connections. We found no pinouts for peripheral sockets. Nine ICs carry no type markings on the schematic. Logic circuitry is shown in functional form, but you cannot tell which functions are in which package. CAI provides no IC list.
According to Bob Swann of CAI, we got the wrong page for table B, so we got no pinout diagrams for the connectors. Bob provided the pin numbers (not marked on the Widget) by phone and promised to have someone call us about the program problems. We’ll let you know when they do so.
Despite these problems, we successfully operated the device. We ran serial echo checks. We also tested the parallel input and output ports. All operations seem correct; we found no bugs other than the unresolved memory issue. In my judgement, the device works with ZX80/81s. We made no tests with MicroAces.