GY-63_MS5611/libraries/MT8870/README.md
2021-12-22 11:05:27 +01:00

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