Follow More by the author: About: www. It uses DC5V voltage to work. When you press the different keys, the loudspeaker will sound that which floor you arrive. This design uses a APR voice chip as the core of the circuit and realizes the function of auto recording and playback.

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Playback and record operations are managed by on chip cir- - Normal cuitry. There are several available messaging modes Modes cannot be mixed. Switching of modes after the device depending upon desired operation. These message modes has recorded an initial message is not recommended.

If determine message management style, message length, and modes are switched after an initial recording has been made external parts count. Therefore, the designer must select the some unpredictable message fragments from the previous appropriate operating mode before beginning the design.

Table 1 defines the decoding necessary to choose the desired mode. This feature is enabled sages by asserting a logic high level on the BE pin. In random access mode Random access mode supports 2, 4, or 8 messages seg- these pins should be considered purely message trig- ments of fixed duration. For a more thorough explanation of the func- length of each message segment is the total recording length tionality of device pins in different modes please refer available as defined by the selected sampling rate divided to the pin description table that appears later in this by the total number of segments enabled as decoded in document.

Random access mode provides easy indexing to When actual recording begins the device responds with a sin- message segments. Mode Recording continues as long as the message pin stays low. The rising edge of the same message trigger pin during On power up, the device is ready to record or play back, in record stops the recording operation indicated with a single any of the enabled message segments. You initiate recording by applying a low If the message trigger pin is held low beyond the end of the level on the message trigger pin that represents the message maximum allocated duration, recording stops automatically segment you intend to use.

The chip then enters low-power mode until pin 7 for message segments respectively. After the message trig- ger pin returns to high, the chip enters standby mode. Transitions on any other message trig- pin goes high again. After recording is finished the device will automatically rewind to the beginning of the most recently recorded message and Functional Description of Playback in Random Access wait for the next user input.

The auto rewind function is con- Mode venient because it allows the user to immediately playback On power up, the device is ready to record or playback, in and review the message without the need to rewind. How- any of the enabled message segments. If a high to low edge occurs on the same mes- new record operation, overwriting the previously existing sage trigger pin during playback, playback of the current message. You can preserve the previously recorded mes- message stops immediately.

A delay equal to 8, cycles of the sample The auto rewind mode allows the user to record over the pre- clock will be encountered before the device starts playing the vious message simply by initiating a record sequence without new message. To record over any other mes- sage however requires a different sequence. A the voice memory. Upon arriving at the desired to the user of the transition between the end and the begin- message a record sequence can be initiated to overwrite the ning of the message.

After you overwrite the mes- sage it becomes the last available message and all previ- Tape Mode ously recorded messages following this message become Tape mode manages messages sequentially much like tradi- inaccessible. If during a record operation all the available tional cassette tape recorders. Within tape mode two options memory is used the device will stop recording automatically, exist, auto rewind and normal.

To proceed from this On power up, the device is ready to record or play back, start- state the user must rewind the device to the beginning of the ing at the first address in the memory array. The device returns to the starting at the first address in the memory array.

You can then initiate a record sequence, as third time, playback of the current message starts again from described above, to record a new message. The most its beginning. A 1, ms period of silence is inserted during loop- message will become inaccessible. If Normal option is necessary the following sequence the beginning of the current message. To listen to a subse- can be used.

To preserve current messages you must fast quent message the device must be fast forwarded past the forward past the messages you want to keep before you can current message to the next message. This function is record a new message. After the device is incremented to the desired message message you wish to overwrite. At this stage you should the user can initiate playback of the message with the play- switch back to record mode and overwrite the desired mes- back sequence described above.

A special case exists when sage. Playback of the last recorded message and all previously recorded messages current message will stop, the device will beep, advance to following this message will become inaccessible. All inputs, the next message and initiate playback of the next message.

To proceed from this state the user must playback of the current message stops immediately. When rewind the device to the beginning of the memory array. If the last recorded message starting at the first address in the memory array.

To exit this state you must pulse recording. A subsequent the beginning of the first message. Lower sampling rates use ment. When controlling messages the microprocessor essen- fewer memory cells and effectively increase the duration tially toggles pins as described in the message management capabilities of the device, but they also reduce incoming sig- sections describe previously.

When this pin is high the device is ready to accept Oscillator frequency can be changed by changing the resis- and execute commands from the host. The APR has a total of eighty memory segments. During 38 KW 6. During playback a low pulse indicates that the 24 KW 8. NOTICE: Rosc table above is for reference only,different Microprocessor control can also be used to link several lots ICs will have somewhat different Rosc value APR devices together in order to increase total available performance..

In this application both the speaker and microphone signals can be connected in parallel. A continuous message can not be recorded in multiple devices however because the transition from one device to the next will incur a delay that is notice- able upon playback.

For this reason it is recommended that message boundaries and device boundaries always coincide. Each memory cell can support voltage ranges from 0 to levels. During playback the stored signals are retrieved from memory, smoothed to form a continuous signal, and then amplified before being fed to an external speaker. The APR automatically filters its input, based on the selected sampling frequency, to meet this requirement.

Sampling rate is determined by The following reference schematics are included as exam- the resistor value on pin 7 OscR. The RC network on pin 19 ples on how a recording system might be designed. The ground return of this bias net- option, and Tape mode - Auto Rewind option. This configuration tors of device status. This is possible because all of these saves power when not recording by shutting off power to the pins and signals were designed to have timing compatible electret microphone.

Figure 3 shows the device configured in tape mode, nor- block the DC biasing voltage.


APR9600 sound recorder IC is no more- Use APR33A3




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