Adopt the dialing demoder conceptual design of embedded DTMF of MSP430
DTMF (Dual Tone Multi-Frequency) signaling is commonly used in telephone networks, including home phones, cellular phones, and SPC exchanges, for transmitting and receiving numbers. DTMF technology is also applicable in scenarios such as power line carrier communication. It is evident that DTMF has extensive applications in dialing and decoding within communication systems. Typically, the detection of DTMF signals is accomplished using specialized chips or digital signal processors (DSPs), which can be costly. This text introduces a low-cost DTMF dialing demodulator based on the MSP430F133 microcontroller, detailing its implementation. The MSP430F133 is a 16-bit RISC architecture MCU from Texas Instruments, featuring a short instruction cycle of 150 ns, 8 KB of Flash ROM, 256 B of RAM, and a built-in 12-bit ADC. DTMF supports 16 characters represented by digits 0-9, letters A-D, and symbols * and #, utilizing eight audio frequency tones. These frequencies are categorized into high-frequency and low-frequency clusters, corresponding to row and column frequencies on the keypad. Each character signal is generated by the superposition of sine wave frequencies from these clusters. The technical specifications for DTMF signals are defined by CCITT Q. 23, specifying a transmission rate of 10 digits per second, with each digit lasting 100 ms during reception. Each signal must persist for at least 45 ms and not exceed 55 ms, with the remaining time being squelch or muting. Frequency deviations must not exceed 1.5%, and signals with deviations over 3.5% are considered invalid. Additionally, under the worst-case detection conditions, the signal-to-noise ratio must be no less than 15 dB. A partial schematic diagram of the DTMF dialing circuit is provided, illustrating the circuit's composition of resistor networks and wave filters formed by four I/O lines. The resistor network creates a 4-bit DAC, while high-pass and low-pass filters combine to form a band-pass filter that processes audio harmonic signals. A voltage transformer interfaces the circuit with the telephone line at a 1:1 ratio of 600 ohms, allowing for adjustment of the outgoing telephone level by changing the resistor value Rx.
The DTMF signaling system operates by generating specific frequency pairs for each key pressed on the keypad. The keypad consists of four rows and four columns, with each intersection corresponding to a specific digit or symbol. The frequencies are carefully selected to ensure minimal interference and maximum clarity during transmission. The high-frequency tones typically range from 1209 Hz to 1477 Hz, while the low-frequency tones range from 697 Hz to 941 Hz. This arrangement prevents confusion between signals and enhances the reliability of the system.
In practical applications, the MSP430F133 microcontroller processes the incoming DTMF signals by sampling them through its built-in ADC. The sampled data is analyzed using algorithms to identify the frequency pairs corresponding to the pressed keys. The low-cost nature of this design makes it suitable for various applications, including home automation systems, remote control devices, and telecommunications equipment, where budget constraints are a concern.
The circuit's design is crucial for achieving accurate signal detection. The resistor network must be carefully calculated to ensure that the DAC output matches the expected voltage levels for the DTMF frequencies. Additionally, the filters must be optimized to allow the desired frequencies to pass while attenuating unwanted noise. The use of a voltage transformer is essential for matching the circuit's impedance with that of the telephone line, ensuring effective signal transmission and reception.
Overall, the DTMF dialing demodulator based on the MSP430F133 microcontroller represents a cost-effective solution for implementing DTMF signaling in various electronic applications, leveraging the microcontroller's capabilities to provide reliable performance in communication systems.DTMF dual tone multifrequency The signal is a commonly used signalling in the telephone network, no matter on home telephones, cellular telephones or SPC exchanges, adopt DTMF signal transmission receiving numbers more. DTMF technology can also be used for occasions such as power line carrier communication, etc. It is obvious, DTMF has extensive ap plication to dial and decode in communication system and others. Usually the detection of DTMF signal is realized by special purpose chip or DSP, but its great of cost. This text has introduced a kind of low-cost DTMF dialing demoder based on MSP430F133 and realized the scheme.
MSP430F133 one 16 the intersection of RISC and the intersection of structure and MCU of TI, most short instruction cycle 150ns, contain 8KB Flash ROM, 256B RAM and built-in 12 ADC. DTMF to amount to 16 character 0~9, A on the dial plate D and * / E, # / F in signal, come on a encoder mode that show with 8 frequency of audiorange.
8 frequency divide into high-frequency cluster and the intersection of low frequency and the intersection of cluster and two set, respectively as list frequently and horizontal frequency. Each signal of character come from list frequently and two superposition of signal of sine of frequency of horizontal frequency.
The mode of combination of the frequency is shown as in Fig. 1. Propose, the technical indicator of DTMF signal is according to CCITT Q. 23: Convey / 10 numbers per second, or each number 100ms in receiving ratio. Each number is conveyed in the course, signal at least 45ms of existence time, and does not exceed 55ms, other time of 100ms are the squelch muting. Allow not to exceed 1. 5% of the frequency errors of in each frequency is clicked. Any exceeds 3. 5% of the signals of of given frequency, is considered void, refuse to admit receiving. In addition, under the worst detection condition, the signal to noise ratio can`t be lower than 15dB.
DTMF dials the partial schematic circuit diagram is shown as in Fig. 2. The circuit is mainly made up of resistor network and electric-wave filter that 4 I/O threads form. The resistor network forms 4 ²s DAC, high-pass filter and low-pass filter make up a band-pass filter and use one pair of audio harmonic signals of filtration. Adopt the voltage transformer to interface with telephone line at 1:1 of 600 on the Ausgang, telephone collinear outgoing level can be regulated through changing Rx.
DTMF dual tone multifrequency The signal is a commonly used signalling in the telephone network, no matter on home telephones, cellular telephones or SPC exchanges, adopt DTMF signal transmission receiving numbers more. DTMF technology can also be used for occasions such as power line carrier communication, etc. It is obvious, DTMF has extensive application to dial and decode in communication system and others. Usually the detection of DTMF signal is realized by special purpose chip or DSP, but its great of cost.
This text has introduced a kind of low-cost DTMF dialing demoder based on MSP430F133 and realized the scheme. MSP430F133 one 16 the intersection of RISC and the intersection of structure and MCU of TI, most short instruction cycle 150ns, contain 8KB Flash ROM, 256B RAM and built-in 12 ADC.
DTMF to amount to 16 character 0~9, A on the dial plate D and * / E, # / F in signal, come on a encoder mode that show with 8 frequency of audiorange. 8 frequency divide into high-frequency cluster and the intersection of low frequency and the intersection of cluster and two set, respectively as list frequently and horizontal frequency.
Each signal of character come from list frequently and two superposition of signal of sine of frequency of horizontal frequency. The mode of combination of the frequency is shown as in Fig. 1. Propose, the technical indicator of DTMF signal is according to CCITT Q. 23: Convey / 10 numbers per second, or each number 100ms in receiving ratio. Each number is con 🔗 External reference
The DTMF signaling system operates by generating specific frequency pairs for each key pressed on the keypad. The keypad consists of four rows and four columns, with each intersection corresponding to a specific digit or symbol. The frequencies are carefully selected to ensure minimal interference and maximum clarity during transmission. The high-frequency tones typically range from 1209 Hz to 1477 Hz, while the low-frequency tones range from 697 Hz to 941 Hz. This arrangement prevents confusion between signals and enhances the reliability of the system.
In practical applications, the MSP430F133 microcontroller processes the incoming DTMF signals by sampling them through its built-in ADC. The sampled data is analyzed using algorithms to identify the frequency pairs corresponding to the pressed keys. The low-cost nature of this design makes it suitable for various applications, including home automation systems, remote control devices, and telecommunications equipment, where budget constraints are a concern.
The circuit's design is crucial for achieving accurate signal detection. The resistor network must be carefully calculated to ensure that the DAC output matches the expected voltage levels for the DTMF frequencies. Additionally, the filters must be optimized to allow the desired frequencies to pass while attenuating unwanted noise. The use of a voltage transformer is essential for matching the circuit's impedance with that of the telephone line, ensuring effective signal transmission and reception.
Overall, the DTMF dialing demodulator based on the MSP430F133 microcontroller represents a cost-effective solution for implementing DTMF signaling in various electronic applications, leveraging the microcontroller's capabilities to provide reliable performance in communication systems.DTMF dual tone multifrequency The signal is a commonly used signalling in the telephone network, no matter on home telephones, cellular telephones or SPC exchanges, adopt DTMF signal transmission receiving numbers more. DTMF technology can also be used for occasions such as power line carrier communication, etc. It is obvious, DTMF has extensive ap plication to dial and decode in communication system and others. Usually the detection of DTMF signal is realized by special purpose chip or DSP, but its great of cost. This text has introduced a kind of low-cost DTMF dialing demoder based on MSP430F133 and realized the scheme.
MSP430F133 one 16 the intersection of RISC and the intersection of structure and MCU of TI, most short instruction cycle 150ns, contain 8KB Flash ROM, 256B RAM and built-in 12 ADC. DTMF to amount to 16 character 0~9, A on the dial plate D and * / E, # / F in signal, come on a encoder mode that show with 8 frequency of audiorange.
8 frequency divide into high-frequency cluster and the intersection of low frequency and the intersection of cluster and two set, respectively as list frequently and horizontal frequency. Each signal of character come from list frequently and two superposition of signal of sine of frequency of horizontal frequency.
The mode of combination of the frequency is shown as in Fig. 1. Propose, the technical indicator of DTMF signal is according to CCITT Q. 23: Convey / 10 numbers per second, or each number 100ms in receiving ratio. Each number is conveyed in the course, signal at least 45ms of existence time, and does not exceed 55ms, other time of 100ms are the squelch muting. Allow not to exceed 1. 5% of the frequency errors of in each frequency is clicked. Any exceeds 3. 5% of the signals of of given frequency, is considered void, refuse to admit receiving. In addition, under the worst detection condition, the signal to noise ratio can`t be lower than 15dB.
DTMF dials the partial schematic circuit diagram is shown as in Fig. 2. The circuit is mainly made up of resistor network and electric-wave filter that 4 I/O threads form. The resistor network forms 4 ²s DAC, high-pass filter and low-pass filter make up a band-pass filter and use one pair of audio harmonic signals of filtration. Adopt the voltage transformer to interface with telephone line at 1:1 of 600 on the Ausgang, telephone collinear outgoing level can be regulated through changing Rx.
DTMF dual tone multifrequency The signal is a commonly used signalling in the telephone network, no matter on home telephones, cellular telephones or SPC exchanges, adopt DTMF signal transmission receiving numbers more. DTMF technology can also be used for occasions such as power line carrier communication, etc. It is obvious, DTMF has extensive application to dial and decode in communication system and others. Usually the detection of DTMF signal is realized by special purpose chip or DSP, but its great of cost.
This text has introduced a kind of low-cost DTMF dialing demoder based on MSP430F133 and realized the scheme. MSP430F133 one 16 the intersection of RISC and the intersection of structure and MCU of TI, most short instruction cycle 150ns, contain 8KB Flash ROM, 256B RAM and built-in 12 ADC.
DTMF to amount to 16 character 0~9, A on the dial plate D and * / E, # / F in signal, come on a encoder mode that show with 8 frequency of audiorange. 8 frequency divide into high-frequency cluster and the intersection of low frequency and the intersection of cluster and two set, respectively as list frequently and horizontal frequency.
Each signal of character come from list frequently and two superposition of signal of sine of frequency of horizontal frequency. The mode of combination of the frequency is shown as in Fig. 1. Propose, the technical indicator of DTMF signal is according to CCITT Q. 23: Convey / 10 numbers per second, or each number 100ms in receiving ratio. Each number is con 🔗 External reference
Related Circuits
The MT8870 is a complete DTMF receiver that integrates both the band-split filter and digital decoder functions. The filter section employs switched capacitor techniques for high and low group filters, while the decoder utilizes digital counting methods to detect...
An audio filter is positioned at the input of each audio integrated circuit (IC) chip to filter the audio signal intended for speakers. A low-pass filter is utilized for the woofer, while a high-pass filter is employed for midrange...
A PIC12F675 microcontroller can switch up to five outputs sequentially using a standard Remote Control pulse input ranging from 1 to 2 ms. While any RC channel input can be utilized, it is particularly effective when paired with rotary...
This series of lectures is designed for individuals with a basic understanding of electronics, such as sophomores in Electrical and Computer Engineering, to explore the field of Embedded Electronics. It is assumed that the reader has a fundamental knowledge...
A company has developed an intelligent temperature monitoring system using the ATMET 89C51 microcontroller. This system automatically records temperature data for a three-phase power supply, including high temperature and other relevant data, functioning as a black box. The ATMET...
The variable frequency power supply is a crucial component of the power system, as its characteristics significantly impact the security and reliability of the overall system. The modern variable frequency power supply is characterized by low power consumption and...