Voice record and Play Back Module

Introduction:

                        In order to save any voice and play the same voice back again we have AUDIO RECORDER AND PLAY BACK module. For saving any audio signals i.e., analog in nature we are using a Re-Recording voice IC called ARP9600. Voice recorder and play back module which uses ARP9600 is shown below:

General Description of ARP9600:

          The APR9600 device offers true single-chip voice recording, non-volatile storage, and playback capability for 40 to 60 seconds. The device supports both random and sequential access of multiple messages. Sample rates are user-selectable, allowing designers to customize their design for unique quality and storage time needs. Integrated output amplifier, microphone amplifier, and AGC circuits greatly simplify system design. The device is ideal for use in portable voice recorders, toys, and many other consumer and industrial applications.     

APLUS integrated achieves these high levels of storage capability by using its proprietary

Analog/multilevel storage technology implemented in an advanced Flash non-volatile memory process, where each memory cell can store 256 voltage levels. This technology enables the APR9600 device to reproduce voice signals in their natural form. It eliminates the need for encoding and compression, which often introduce distortion.

Features:

Single-chip, high-quality voice recording & playback solution

- No external ICs required

- Minimum external components

• Non-volatile Flash memory technology

- No battery backup required

• User-Selectable messaging options

- Random access of multiple fixed-duration messages

- Sequential access of multiple variable-duration messages

• User-friendly, easy-to-use operation

- Programming & development systems not required

- Level-activated recording & edge-activated play back switches

• Low power consumption

- Operating current: 25 mA typical

- Standby current: 1 uA typical

- Automatic power-down

• Chip Enable pin for simple message expansion

PIN DIAGRAM OF ARP9600:

                                                 

                                        

FUNCTIONAL DESCRIPTION:

APR9600 block diagram is included in order to describe the device’s internal architecture. At the left hand side of the diagram are the analog inputs. A differential microphone amplifier, including integrated AGC, is included on-chip for applications requiring use. The amplified microphone signals fed into the device by connecting the ANA_OUT pin to the ANA_IN pin through an external DC blocking capacitor. Recording can be fed directly into the ANA_IN pin through a DC blocking capacitor, however, the connection between ANA_IN and ANA_OUT is still required for playback. The next block encountered by the input signal is the internal anti-aliasing filter. The filter automatically adjusts its response according to the sampling frequency selected so Shannon’s Sampling Theorem is satisfied. After anti-aliasing filtering is accomplished the signal is ready to be clocked into the memory array. This storage is accomplished through a combination of the Sample and Hold circuit and the Analog Write/Read circuit. These circuits are clocked by either the Internal Oscillator or an external clock source. When playback is desired the previously stored recording is retrieved from memory, low pass filtered, and amplified as shown on the right hand side of the diagram. Thesignal can be heard by connecting a speaker to the SP+ and SP- pins. Chip-wide management is accomplished through the device control block shown in the upper right hand corner. Message management is provided through the message control block represented in the lower center of the block diagram.

ARP9600 BLOCK DIAGRAM:

 Message Management: 

Message Management General Description:

          Playback and record operations are managed by on-chip circuitry. There are several available messaging modes depending upon desired operation. These message modes determine message management style, message length, and external parts count. Therefore, the designer must select the appropriate operating mode before beginning the design. Operating modes do not affect voice quality; for information on factors affecting quality refer to the Sampling Rate & Voice Quality section. The device supports five message management modes (defined by the MSEL1, MSEL2 and /M8_OPTION pins shown in above two figures.

Random access mode with 2, 4, or 8 fixed-duration messages Tape mode, with multiple

 Variable-duration messages, provides two options:

- Auto rewind

Random Access Mode:

Random access mode supports 2, 4, or 8 Message segments of fixed duration. As suggested recording or playback can be made randomly in any of the selected messages. The length of each message segment is the total recording length available (as defined by the selected sampling rate) divided by the total number of segments enabled (as decoded in Table1). Random access mode provides easy indexing to message segments.

Functional Description of Recording in Random Access Mode:

              On power up, the device is ready to record or playback in any of the enabled message

segments. To record, /CE must be set low to enable the device and /RE must be set low to enable recording. You initiate recording by applying a low level on the message trigger pin that represents the message segment you intend to use. The message trigger pins are labeled /M1_MESSAGE - /M8_OPTION on pins 1-9 (excluding pin 7) for message segments 1-8 respectively.

Note: Message trigger pins of M1_MESSAGE, /M2_NEXT, /M7_END, and /M8_OPTION have expanded names to represent the different functionality that these pins assume in the other modes. In random access mode these pins should be considered purely message trigger pins with the same functionality as /M3, /M4, /M5, and /M6. For a more thorough explanation of the functionality of device pins in different modes please refer to the pin description table that appears later in this document. When actual recording begins the device responds with a single beep (if the BE pin is high to enable the beep tone) at the speaker outputs to indicate that it has started recording. Recording continues as long as the message pin stays low. The rising edge of the same message trigger pin during record stops the recording operation (indicated with a single-beep). If the message trigger pin is held low beyond the end of the maximum allocated duration, recording stops automatically (indicated with two beeps), regardless of the state of the message trigger pin. The chip then enters low-power mode until the message trigger pin returns high. After the message trigger pin returns to high, the chip enters standby mode. Any subsequent high to low transition on the same message trigger pin will initiate recording from the beginning of the same message segment. The entire previous message is then overwritten by the new message, regardless of the duration of the new message. Transitions on any other message trigger pin or the /RE pin during the record operation are ignored until after the device enters standby mode.          

Functional Description of Playback Random Access Mode:

On power up, the device is ready to record or playback, in any of the enabled message

segments. To playback,/CE must be set low to enable the device and /RE must be set high to disable recording & enable playback.You initiate playback by applying a high to low edge

on the message trigger pin that represents the message segment you intend to playback.

Playback will continue until the end of the message is reached. If a high to low edge occurs

on the same message trigger pin during playback, playback of the current message stops

immediately. If a different message trigger pin pulses during playback, playback of the current message stops immediately (indicated by one beep) and playback of the new message segment begins. A delay equal to 8,400 cycles of the sample clock will be encountered before the device starts playing the new message. If a message trigger pin is held low, the selected message is played back repeatedly as long as the trigger pin stays low. A period of silence, of a duration equal to 8,400 cycles of the sampling clock, will be inserted during looping as an indicator to the user of the transition between the end and the beginning of the message.

Tape Mode :

Tape mode manages messages sequentially much like traditional cassette tape recorders.

Within tape mode two options exist, auto rewind and normal. Auto rewind mode configures

the device to automatically rewind to the beginning of the message immediately following

recording or playback of the message. In tape mode,using either option, messages must be

recorded or played back sequentially, much like a traditional cassette tape recorder.

 Function Description of Recording in Tape Mode using the Auto Rewind Option:

On power up, the device is ready to record or playback,starting at the first address in the  memory array. To record, /CE must be set low to enable the device and /RE must be set low to enable recording. A falling edge of the /M1_MESSAGE pin initiates voice recording  (indicated by one beep).A subsequent rising edge of the /M1_MESSAGE pin during recording stops the recording (also indicated by one beep). If the M1_MESSAGE pin is held low beyond the end of the available memory, recording will stop automatically (indicated by two beeps). The device ill then assert a logic low on the /M7_END pin until the /M1 Message pin is released. The device returns to standby mode when the /M1_MESSAGE pin goes high again.After recording is finished the device will automatically rewind to the beginning of the most recently recorded message and wait for the next user input. The auto rewind function is convenient because it follows the user to immediately playback and review the message without the need to rewind. However, caution must be practiced because a subsequent record operation will overwrite the last recorded message unless the user remembers to pulse the /M2_Next pin in order to increment the device past the current message.  A subsequent falling edge on the /M1_Message pin starts a new record operation, overwriting the previously existing message. You can preserve the previously recorded message by using the /M2_Next input to advance to the next available message segment. To perform this function, the /M2_NEXT pin must be pulled low for at least 400 cycles of the sample clock.The auto rewind mode allows the user to record over the just recorded  message simply by initiating a record sequence without first toggling the /M2_NEXT pin.

Function Description of Playback in Tape Mode using Auto Rewind Option:

           

            On power-up, the device is ready to record or playback, starting at the first address in the memory array. Before you can begin playback, the /CE input must be set to low to enable the device and /RE must be set to high to disable recording and enable playback. The first high to low going pulse of the /M1_MESSAGE pin initiates playback from the beginning of the current message; on power up the first message is the current message. When the /M1_MESSAGE pin pulses low the second time, playback of the current Message stops immediately. When the /M1_MESSAGE pin pulses low a third time, playback of the current message starts again from its beginning. If you hold the /M1_MESSAGE pin low continuously the same message will play continuously in a looping fashion. A 1,540ms period of silence is inserted during looping as an indicator to the user of the transition between the beginning and end of the message. Note that in auto rewind mode the device always rewinds to the beginning of the current message. To listen to a subsequent message the device must be fast forwarded past the current message to the next message. This function is accomplished by toggling the /M2_NEXT pin from high to low. The pulse must be low for least 400 cycles of the sampling clock. After the device is incremented to the desired message the user can initiate playback of the message with the playback sequence described above. A special case exists when the /M2_NEXT pin goes low during playback. Playback of the current message will stop, the device will beep, advance to the next message and initiate playback of the next message. (Note that if /M2 Next goes low when not in playback mode, the device will prepare to play the next message, but will not actually initiate playback).

If the /CE pin goes high during playback, playback of the current message will stop, the device will beep, reset to the beginning of the first message, and wait for a subsequent playback command. When you reach the end of the memory array, any subsequent pulsing of /M1_MESSAGE or /M2_NEXT will only result in a double beep. To proceed from this state the user must rewind the device to the beginning of the memory array. This can be accomplished by toggling the /CE pin low or cycling power.

Sampling Rate & Voice Quality:

According to Shannon's sampling theorem, the highest possible frequency component introduced to the input of a sampling system must be equal to or less than half the sampling frequency if aliasing errors are to be eliminated. The APR9600 automatically filters its input, based on the selected sampling frequency, to meet this requirement. Higher sampling rates increase the bandwidth and hence the voice quality, but they also use more memory

cells for the same length of recording time. Lower sampling rates use fewer memory cells

and effectively increase the duration capabilities of the device, but they also reduce incoming signal bandwidth. The APR9600 accommodates sampling rates as high as 8 kHz and as low a 4 kHz. You can control the quality/duration trade off by controlling the sampling frequency. An internal oscillator provides the APR9600 sampling clock. Oscillator frequency can be changed by changing the resistance from the OscR pin to GND. Table 2 summarizes resistance values and the corresponding sampling frequencies, as well as the resulting input bandwidth and duration.

Table 2 Resistance Values & Sampling Frequencies

Sampling Application:

The following reference schematics are included as examples of how a recording system

might be designed. Each reference schematic shows the device incorporated in one of its three main modes: Random Access, Tape mode – Normal option, and Tape mode – Auto Rewind option. Note that in several of the applications either one or all of the /BUSY,  /STROBE, or /M7_END pins are connected to LEDs as indicators of device status. This is possible because all of these pins and signals were designed to have timing compatible with both microprocessor interface and manual LED indication. A bias must be applied to the electrets microphone in order to power its built-in circuitry. The ground return of this bias network is connected to the /Busy.

This configuration saves power when record mode. Both pins 18 and 19, MicIn and MicRef, must be AC coupled to the microphone network in order to block the DC biasing voltage. Figure 3 shows the device configured in random access mode. The device is using eight Message segments, the maximum available, in this mode. Note that message trigger pins that are not used, for modes with less than eight segments, can be left unconnected with the exception of pin /M8_OPTION which should be pulled to VCC through a 100k resistor.

Random Access Mode:   2 / 4 / 8 Message