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79 lines
2.6 KiB
Markdown
79 lines
2.6 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/MT8870/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/MT8870/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/MT8870/blob/master/LICENSE)
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[](https://github.com/RobTillaart/MT8870/releases)
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# MT8870
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Arduino library for MT8870 DTMF decoder (breakout).
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## Description
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This library reads the signals of the MT8870 chip.
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If data is available one can read it raw or as text.
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DTMF = Dual Tones Multiple Frequency.
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These are the tones you hear when you press buttons on your phone.
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DTMF tones, uses one from A..D and one from E..H.
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| Name | Frequency |
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|:------:|------------:|
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| A | 697 Hz |
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| B | 770 Hz |
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| C | 852 Hz |
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| D | 941 Hz |
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| E | 1209 Hz |
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| F | 1336 Hz |
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| G | 1477 Hz |
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| H | 1633 Hz |
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## Interface
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- **MT8870()** constructor
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- **void begin(uint8_t STQ, uint8_t Q1, uint8_t Q2, uint8_t Q3, uint8_t Q4)** defines which pins to use.
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Technically it is possible to have readout multiple decoders
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with one MT8870 object by calling **begin()** with other pins.
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- **STQ** = data available signal
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- **Q1..Q4** = data pins.
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- Calling begin resets the **lastRead** char
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- **bool available()** returns true if there is a DMTF signal
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- **char read()** reads the character available. returns 255 if no signal available.
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- **uint8_t readRaw()** returns 0 .. 15 or 255 if no signal is available.
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- **uint8_t lastRaw()** returns the last code read 0 .. 15 or 255 if no signal available.
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Note this is a cached value from a readRaw / read call.
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- **uint32_t lastTimeRead()** returns the timestamp of last **read()** or **readRaw()**.
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## Operations
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See examples.
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## Future
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#### must
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- improve documentation
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- keypad matrix, which key generates which tones
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#### should
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- test setup
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- add examples
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- DMTF with a PCF8574
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- DMTF as secret key
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- DMTF with less keys (less pins)
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- DMTF over interrupt triggered by STQ line
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#### could
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- buffer like Serial? (how to fill? interrupt? example sketch?)
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- read part of stream interface?
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- DMTF tone generation?
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- MCP_DAC
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- PWM + HW?
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