Musical doorbell on AY8910 sound coprocessor. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Calls and audio simulators

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In recent years, many different musical calls have been described on the pages of "Radio". In most cases, they are quite simple and the result, of course, is not entirely satisfactory. The variant with the use of microprocessors offered to the attention of readers is more complex, but it has great potential. The device performs the function of a doorbell, however, after minimal refinement and selection of favorite melodies, other uses can be found for it.

The musical bell is assembled from parts of SPECTRUM-compatible computers. This made it possible to achieve good results. The scheme of the device is shown in fig. 1.

(click to enlarge)

On the elements DD5.1 ​​- DD5.3 made master generator. Elements DD6.1-DD6.3 form the port of the audio coprocessor, to control which only the signal A14 is analyzed. The choice of address is due to the desire of the authors to maintain compatibility with the ZX-SPECTRUM computer, which makes it possible to use a large number of existing programs and melodies. At the same time, the control of the sound coprocessor has not changed:

LD BC,65533: OUT C, A - register selection;

LD BC, 49149: OUT C, A - register entry;

LD 60,65533: IN C, A - reading from the register.

The purpose of the audio coprocessor registers is described in detail in [1, 2]. The contents of register C are not important here. It is used at will.

On the elements DD7, DD5.4, DD5.5 and diodes VD2, VD3, a memory management unit is assembled. The RAM signal generated by it activates the RAM in case of memory access within addresses F800H-FFFFH (63488-65535). Otherwise, select ROM. If it is not intended to use a ROM with a capacity of more than 32 KB, the design can be simplified. To do this, remove the DD7 chip, apply the A2 signal from the processor to the VD15 diode cathode (leave the resistor R5), apply the MR signal to the CS input of the DD2 ROM (pin 20), and the A0 signal to the 22E input (pin 15). A diagram of a simplified memory management node is shown in fig. 2. It should be borne in mind that the memory field will now have 16 mappings of the same RAM. Thus, the addresses 8000H, 8800H, 9000H-F800H are equivalent.

Any ZQ1 quartz resonator with a frequency of 2 MHz is applicable in the design. Chips are interchangeable with their many counterparts. Diodes - any series KD521, KD522. The resistance values ​​​​of resistors and the capacitance of capacitors can be changed over a wide range. You may have to choose the resistance of resistors R1 - for stable operation of the generator and R18 - for the optimal volume level. Blocking capacitors C3-C9 are installed on the microcircuit power conductors, preferably closer to their cases. Switches: SB1 - call button; SF1 is mounted on the door frame, or any isolating switch is used (the circuit is open when the door is closed).

It is best to install a three-prong reed switch controlled by a magnet, as is done in burglar alarms. A bell sounds when the door is opened and closed. It can be disabled by connecting the PA2 output (pin 19) of the audio coprocessor to a common wire. The effect is implemented in software (Table 1).

The device is assembled on a ready-made board from a SPECTRUM-compatible computer or AON. It already has places for installing RAM, ROM and processors, as well as power conductors, information and address lines. The finished device, power supply and amplifier are conveniently placed in the case of a radio or tape recorder.

Establishing a call begins with checking the installation. Connect the power supply and amplifier. Next, you need to write the TEST program (Table 2) to a ROM of any size (see [3]). If after sending the RESET command to the processor you hear a bell - everything is in order (perhaps, except for the RAM). Otherwise, either the generator does not start, or the parts are faulty or the installation is incorrectly performed. To check the RAM, write zero values ​​​​at addresses 0001H, 0002H. If the bell rings, then the RAM is working properly, if not, try replacing the VD1 diode with two connected in series.

Then you should program a musical call. To do this, perform the following steps.

Using the SOUND TRACKER V3.0 music editor, you need to load any compiled melody at 63488 by selecting the "WITH PLAYER" command.

In BASIC, execute the command CLEAR 4E4.

From the TR-DOS operating system, execute the commands:

• LOAD "name" CODE (where "name" is the name of the loaded file);
• SAVE "player" CODE 63564,1116;
• Download ringtones by selecting the command "WITHOUT PLAYER";
• Write the text of the program PROG.

Merge the resulting files into one by placing in it:

• PROG program starting from address 0000H (00000);
• the player program, starting at address 0200H (00512);
• compiled melodies in free ROM memory (except for F800H-FFFFH addresses);
• immediately after the PROG program, a table with the addresses of melodies, ending it with the word FFFFH. The length of the table is any within 2-182 bytes (1-91 melodies).

If the free space of the ROM and the address tables are filled with FFH codes, without erasing the "firmware", you can add a new melody to the free space and write its address to the end of the table.

The PROG program uses the following constants:

• 00D7H 00D8H - defines the delay time for debouncing the SB1 switch contacts: 13*{(00D8H)*256+(00D7H)), in microseconds;
• 0086Н 0087Н - determines the period of time between calls to the program player 13*{(0087H)*256+(0086H)}, in microseconds (approximately 0,02 s), then the period between notes is -DELAY- times greater (hereinafter in signs - - the parameter of the music editor SOUND TRACKER is enclosed);
• 00F7H - contains the -LENGTH- parameter when -PATTERNS LENGTH- is 63, i.e. (00F7H)*64 is the number of notes played before stopping by itself.

For rational use of ROM memory, it is advisable to pre-adjust the length of melodies in the SOUND TRACKER editor to the contents of cell 00F7H. If the melody is shorter, after one loss it will start over and play the required (00F7H) * 64 notes (of course, provided that the door remains closed); and if it is longer, the end of the melody will not sound.

Instead of the SOUND TRACKER editor, you can use another version, adjusting, if necessary, some constants in the PROG program:

• (000ВН,000СН) - length of the player program;
• (0055Н,0056Н) - the address at which the address of the current melody is entered into the initialization procedure;
• (0062Н,0063Н) - address of the initialization procedure;
• (0083Н,0084Н) - address of the player procedure;
• (00SAN,00SVN) - address of the mute procedure.

The call sometimes creates interference in the form of stripes on the TV screen. Their level can be reduced by galvanically decoupling the bell and the wires going to the button and the door sensor. This can be done using two AOT110 optocouplers, a galvanic cell from a wristwatch and several resistors. When the door is closed and the button is not pressed, the circuits are open and the battery is not discharged. You can also advise to improve the clock generator, the RAM sampling and power supply unit, the startup and reset unit.

Literature

1. Larchenko A., Rodionov N. ZX Spectrum & TR-DOS for users and programmers. - S.-Pb.: PETER, 1994.
2. Kostinevich R. Music coprocessor AY-3-8910 on "Vector-O6ts". - Radio amateur, 1995, No. 5, p. 25.
3. Borovik O., Parfenov A., Syryamkin V. Fascinating games on a household computer. - Tomsk: MGP "Rasko", 1992.

Authors: V. Ogleznev, V. Tolstukhin, Izhevsk

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