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RS232 For Sharp Pocket Computers Schematic Circuit Diagram

Programming Interface for Pocket Computer

RS232 for Sharp pocket computers: The programming aspect entails an interface that can establish a connection with a specialized cassette interface. The signals present at this interface bear a striking resemblance to those found in an RS232 interface. However, they are inverted and feature distinct logic levels. Establishing a link between the pocket computer and a larger computer via this interface would be highly beneficial. Such connectivity would significantly enhance the convenience of writing, modifying, and storing software. Achieving this connectivity merely necessitates a modest circuit.

The sole 5 V supply voltage undergoes conversion into ±10 V through the use of 1C1. Leveraging these voltages, the buffers within IC1 can seamlessly transform the logic signals originating from the pocket computer into RS232 levels. The inversion of these levels is orchestrated by four inverters housed in IC1. Remarkably, the circuit’s power consumption is a mere 30 mA, rendering it easily supplyable from the larger computer.

Connector Challenges for Interface Link to Pocket Computer

Connecting the interface to my pocket computer introduces a slight inconvenience due to the somewhat unconventional pitch (1.27) of the connector. Connectors featuring this pitch are typically too lengthy for this particular application, necessitating the somewhat unconventional approach of cutting one to the required size. The circuit underwent testing under the XON/XOFF protocol at 2400 baud, with even parity, 8 data bits, and a stop bit. However, at higher speeds, minor issues surfaced. It’s worth noting that the occurrence of such problems depends on the specific software in use.

The interface of the Sharp pocket computer is set with:
OPEN” COM:2400, E, 8, 1, A, L, and H1A, X, N”: CLOSE.

RS232 for Sharp pocket computers Schematic diagram

RS232

RS-232 or Recommended Standard 232 is a standard originally introduced in 1960 for the serial communication transmission of data. It formally defines signals connecting between a DTE (data terminal equipment), such as a computer terminal, and a DCE (data circuit-terminating equipment or data communication equipment), such as a modem. The standard defines the electrical characteristics and timing of signals, the meaning of signals, and the physical size and pinout of connectors. The current version of the standard is TIA-232-F Interface Between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange, issued in 1997. The RS-232 standard had been commonly used in computer serial ports and is still widely used in industrial communication devices.

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