The RS-232 Serial Data Adapter for the RFC-1/B was originally designed to be used with a modem not a printer. This makes it slightly more difficult, but not impossible, to use with an inexpensive parallel printer.
Printer Selection
True parallel printers are remarkably standard devices and users have little trouble with the vast majority of parallel printers. In fact, most problems can be traced to mistakes in wiring or equipment setup.
A relatively new class of extremely inexpensive printers sometimes called Windows printers are available. Typically these printers have only a USB interface which will not work with the RFC-1/B. Aside from the interface, the problem with these devices (and what makes them so cheap) is that are just a print engine that is unable to print without a personal computer to provide the intelligence for the engine. This type of printer will not work with the RFC-1/B.
The RFC-1/B treats all printers as continuous paper feed--it does not generate page feeds. It sends a continuous stream of data with carriage returns and line feeds. Most printers will automatically generate page feeds which allows for more efficient paper usage. Occasionally a printer will refuse to dump the final data from the buffer until the page is full. In this case there is usually an option is the printer setup that will make it print the final data from buffer.
(If you happen to have an old printer lying around that you bought from a wire service that you no longer use, it may be a serial printer. You will need the manual for the printer to set it up properly--we cannot provide printer documentation.)
Data Converters
To use a parallel printer with the RS-232 serial interface, the data must be converted from a serial data stream to parallel. Some printer manufacturers offer this as an option for their printers. Call your vendor or the printer manufacturer to find out if such an accessory is available for your printer. Many third party devices are also available that perform this task. Your local computer superstore or catalog warehouse will probably have one. Other possible sources include: Black Box, Global Computer, Jameco, and Patton Electronics.
Our early experiences showed that wall powered adapters were more reliable in this application than so-called "self-powered" devices that draw power from unused data lines on the peripheral port. However newer devices consume very little power and may work just as well. A converter with a small memory buffer is preferred over a non-buffered device.
The serial to parallel data converter should be set to receive serial data at 300,8,N,1 and it should be set as a DCE device. We suggest 300 baud because it allows the printer to keep up with the data stream. A higher data rate may be used if the printer has a buffer.
The following is a typical list of steps required to install a parallel printer with a generic serial to parallel converter to an RFC-1/B with the RS-232 adapter already installed. This setup is for local printing only.
- Verify that the DIP switches on the serial to parallel converter are set for 300 bps, 8 data bits, no parity, and software (or no) handshaking. Also, make sure that the DCE/DTE switch is in the DCE position.
- Plug one end of a 25 pin D cable to the RS-232 adapter on the RFC-1/B.
- Plug the other end of the cable into the serial input side of the serial to parallel data convertter.
- Attach the serial to parallel converter directly to the Centronics type parallel input of the printer or use a short printer cable to attach the parallel output of the data converter to the printer.
- Apply power to the RFC-1/B and the printer and the converter if it uses an external supply.
- Set the RFC-1/B baud rate to 300. This is done by programming a value of 5 at address 1005 in the RFC-1/B memory. Consult the instructions that came with your RFC-1/B for programming information.
- Program the RFC-1/B to send readings to the printer at scheduled intervals by programming an action sequence and setting up the proper date and time triggers for that action sequence. Consult the instructions that came with your RFC-1/B for programming information.
