KT0803

Arduino Library for KT0803 and KT0803K FM transmitter.

Legal point of attention

In different countries there are different laws with respect to using transmitting devices and their range. Please inform yourself of the local rules and laws if and how you may or may not use a device like the KT0803 in your projects, either hobby, commercial or otherwise.

Description

This experimental library allows basic control of the KT0803 and / or the KT0803K FM transmitter device. It is primary written to understand the possibilities and the interface of the device.

The library is not tested by me with hardware yet. See future below.

There are newer, more capable, follow up devices like model K, L and M. From these only the KT0803K is supported as a derived class. The L and the M versions of the device will work with the KT0803K class too as their functionality is equal or exceeds the K version. As far as investigated the L and M versions are backwards compatible.

Version 0.3.0 implements a few KT0803K specific functions, see section below. These will work for L and M devices too.

For ATTinyX5 series there exists the TinyKT0803 class which is derived from this one. It uses a different I2C implementation. See - https://github.com/RobTillaart/TinyKT0803

Hardware

Read datasheet for details.

Warning The KT0803 is an 3.3 Volt device and cannot be connected directly to 5V MCU's.

                   +----------+
                   |  KT0803  |
             GND --|  1   16  |-- PA_OUT  RF analog output
   Crystal    XI --|  2   15  |-- GND
   Crystal    XO --|  3   14  |-- SCL     I2C Clock
   3.3V    IOVDD --|  4   13  |-- SCA     I2C Data
             GND --|  5   12  |-- GND
   in left   INL --|  6   11  |-- GND
   in right  INR --|  7   10  |-- RSTB    Reset
   enable     SW --|  8    9  |-- GND
                   |          |
                   +----------+

Frequency range

The frequency range stated on the front page of the datasheet ==> 70 MHz - 108 MHz. The frequency range stated in table 2 ==> 76 MHz - 108 MHz. So the datasheet is at least ambiguous on this point.

Keep in mind that the frequency range allowed differs per country. The library does not provide this filtering, explicit responsibility of the user.

Differences

The KT0803K device has far more options, which are not all implemented. There is one important, the resolution or step-size of the frequency.

device	step-size	Notes
KT0803	100 KHz	in code all math is done with 50 KHz
KT0803K	50 KHz

Backwards compatible. According to the datasheet code for the KT0803 should work for the KT0803K. Code with the KT0803K class will probably not work on a KT0803.

Transmit frequency

The transmit frequency can be set with setFrequency(MHz) or by setChannel(channel). Note that the channel and frequency math of the KT0803 and the KT0803K is aligned in this library. This allows exchange of channel data between device types.

Note that the KT0803 will internally round to use 100 KHz steps.

Some examples:

Frequency	Channel	Notes
70.00 MHz	1400	channel = freq (Mhz) * 20
70.05 MHz	1401	freq = channel * 0.05
70.10 MHz	1402
76.00 MHz	1520
80.00 MHz	1600
89.70 MHz	1794	default (see registers datasheet)
100.00 MHz	2000
101.30 MHz	2026
105.70 MHz	2114
108.00 MHz	2160

Interface KT0803

#include "KT0803.h"

Constructor

KT0803(TwoWire *wire = &Wire) constructor, optional Wire interface.
KT0803K(TwoWire *wire = &Wire) constructor, optional Wire interface.
bool begin(float freq = 90.0, bool mute = true) initializes the library. Furthermore it checks if the deviceAddress is available on the I2C bus. Default it sets the frequency to 90 MHz and mutes the signal. Returns true if deviceAddress is found on the bus, false otherwise.
bool isConnected() test to see if deviceAddress is found on the I2C-bus.

Frequency

bool setFrequency(float MHz) converts the frequency in MHz to call setChannel(channel). The value of channel is rounded off depending on the resolution of the device. Returns false if MHz is out of range or setChannel() fails.
float getFrequency() returns the current frequency in MHz, can be slightly different from the set value due to rounding math mentioned above. The return value is derived from a call to getChannel()
bool setChannel(uint16_t channel) writes the channel to broadcast on to the device. This involves two or three writes to different device registers.
uint16_t getChannel() reads the selected channel from the device and returns it.

PGA

Read Datasheet.

The KT0803K has a PGA_LSB (2 bits) setting, which allows setting the gain with single (1) dB steps. This is not yet implemented in the library.

bool setPGA(uint8_t pga) sets gain according to table below. Returns false if pga is out of range (0..7).
uint8_t getPGA() returns 0..7, default 0.

PGA	gain	notes
111	12dB
110	8dB
101	4dB
100	0dB
000	0dB	default
001	-4dB
010	-8dB
011	-12dB

RFGain

Read Datasheet.

Note: the RFGain value (4 bits) is distributed over three registers. PA_BIAS (register 0x05) is only supported in the KT0803K device. It is not yet supported in the library.

bool setRFGain(uint8_t rfgain) sets rfgain according to table below. Returns false if rfgain is out of range (0..15).
uint8_t getRFgain() returns 0..15, default 15.

RFGAIN	RFout	PA_BIAS = 1	notes
0000	95.5 dBuV	-
0001	96.5 dBuV	-
0010	97.5 dBuV	-
0011	98.2 dBuV	-
0100	98.9 dBuV	-
0101	100.0 dBuV	-
0110	101.5 dBuV	-
0111	102.8 dBuV	-
1000	105.1 dBuV	107.2 dBuV
1001	105.6 dBuV	108.0 dBuV
1010	106.2 dBuV	108.7 dBuV
1011	106.5 dBuV	109.5 dBuV
1100	107.0 dBuV	110.3 dBuV
1101	107.4 dBuV	111.0 dBuV
1110	107.7 dBuV	111.7 dBuV
1111	108.0 dBuV	112.5 dBuV	default

Region selection

Read datasheet for details.

Note that not all frequencies are allowed in all regions / countries!

The first four are convenience wrappers for setPHTCNST() If some region is missing please let me know the details and I can add a wrapper for it.

void setEurope()
void setAustralia()
void setUSA()
void setJapan()
bool setPHTCNST(bool on) See table below.
bool getPHTCNST() returns set value.

PHTCNST	time	Region
0	75 μs	USA, Japan, (default)
1	50 μs	Europe, Australia

PilotToneAdjust

Read datasheet.

bool setPilotToneAdjust(uint8_t mode) HIGH = 1 LOW = 0
uint8_t getPilotToneAdjust()

Mute

Default the device is not muted, but begin() will default mute it. See interface section above.

bool setMute(bool mute) enables or disables the transmitting by muting the signal.
bool getMute() returns the current state of muting.

Preference channels

The device and library do not implement the persistant store of user selectable preferences (frequencies or channels). This can be implemented by the user in EEPROM or another persistent medium.

Think of a class that holds an array of channels and optional descriptions. A minimal hardcoded preset sketch is in the examples.

Derived classes

A derived class KT0803K class is created, with some extended functions.

The KT0803L will work as it is backwards compatible with KT0803K. It has far more registers in use than the KT0803/K.

The KT0803M is identical to the KT0803K (no new registers), so a derived class is straightforward.

Interface KT0803K

Added functions in 0.3.0 (not tested), check datasheet.

Mono Stereo

bool setMono() idem
bool setStereo() idem
bool isStereo() idem

Bass

**bool setBass(uint8_t bass); // 0..3 = 0, 5, 11, 17 dB
uint8_t getBass() idem

Misc

bool powerOK() idem
bool silenceDetected() idem

Future

Must

improve documentation
buy hardware
test and verify.

Should

update readme.md
- KT0803K specific functions.
add examples for KT0803K specific functions.

Could

RESET pin as optional parameter in constructor?
SW pin (ON/OFF) as optional parameter in constructor?
- add functions for sw on/off,
- what is impact on settings?
- call begin () again? => default
- explain well doc.
derived class KT0803M == KT0803K
derived class KT0803L >= KT0803K (compatible)
improve error handling
unit tests possible?
extend settings upon request bold are interesting, see table

device	setting	register	Notes
KT0803	PA_CTRL	13, bit 2	WARNING in datasheet
			Should it be added in API?
KT0803K	PGA_LSB	04, bit 4+5	gain fine tuning -> see PGA_MOD
KT0803K	FDEV	04, bit 2+3	Frequency deviation adjustment
KT0803K	PDPA	0B, bit 5	Power Amplifier Power Down ?
KT0803K	PA_BIAS	0E, bit 1	PA bias current enhancement.
KT0803K	LMTLVL	10, bit 3+4	Internal audio limiter level control
KT0803K	PGAMOD	10, bit 0	PGA mode selection (use PGA_LSB/ not)
KT0803K	SLNCDIS	12, bit 7	Silence detection disable
KT0803K	SLNCTHL	12, bit 4+5+6	Silence detection low threshold
KT0803K	SLNCTHH	12, bit 1+2+3	Silence detection high threshold
KT0803K	SW_MOD	12, bit 0	Switching channel mode selection
KT0803K	SLNCTIME	14, bit 5+6+7	silence detection time
KT0803K	SLNCCNTHIGH	14, bit 2+3+4	silence detection count high
KT0803K	SLNCCNTLOW	15, bit 0+1+2	silence detection count low

Wont (for now)

investigate tea5767 FM receiver (Out of scope for this lib).
investigate efficiency of register access.
- caching all (allowed) registers in begin()
  - 3 bytes for KT0803
  - 12 bytes for KT0803K
- cache frequency.
- only writing is needed.
send binary data over FM?
preset frequency array in .h file (hardcoded)
enums for parameters - readability?

Support

If you appreciate my libraries, you can support the development and maintenance. Improve the quality of the libraries by providing issues and Pull Requests, or donate through PayPal or GitHub sponsors.

Thank you,

RobTillaart/KT0803