uBITX AGC - Adafruit TPA2016, A Success! #ubitx
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Hi Group.
Now, I haven't tried many AGC solution on the uBITX, only 2, the VK3YE, and ADAFRUIT TPA2016 I2C module. The VK3YE solution I found messed with the audio quality, made it all scratchy, and still didnt handle local 100w stations well... Now after playing with the TPA for a few days I am very happy with the results. Audio has good depth and AGC is reponsive, also gives a nice increase in gain. One trick to others who want to impliment this, you will need to add some code to the Adafruit library to implement the enableNoiseGate(false); function. We need to turn the NoiseGate off or else the AGC will not ramp up with only background noise and you will not hear anything until a loud signal comes on. Also the speaker output is NOT grounded, you need to isolate you SPK jack so that the - from the TPA2016 are direct to the speaker with no chassis grounding... Best part in my opinion, is that ALL the AGC related settings are customisable if your want, if not, just use the voice settings from the datasheet, I have and they work great! I will post up some code tonight... and a few pics.... 73, Nick VK4PLN |
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Which 2 boards?? I know the one is the TAP2016.? What's the other?
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73, Michael KM4OLT On Fri, Feb 2, 2018 at 06:13 pm, Nick VK4PLN wrote:
Hi john, both boards from eBay... |
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/***
? VK4PLN's AGC Code. Adafruit TPA2016
Add call to setupTPA2016(); to main code setup() in ubitx_20 after initOscillators();
/
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#include <Wire.h>
#include "Adafruit_TPA2016.h"
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Adafruit_TPA2016 audioamp = Adafruit_TPA2016();
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void setupTPA2016() {
??
? audioamp.begin();
? // See Datasheet page 22 for value -> dBV conversion table
//? Serial.println("Right off, Left On,");
? audioamp.enableChannel(false, true);
?
? // Noise Gate Threshold: Below this value, the AGC holds the gain to prevent breathing effects.
? //Select the threshold of the noise gate (1,4,10,20mV) (0-3)
//? Serial.println("Noise Gate Threshold,");
? //Disable NoiseGate, we want to hear everything, even weak signals....
? audioamp.enableNoiseGate(false);
? audioamp.setNoiseGateThreshold(0);
??
? // Fixed Gain: The normal gain of the device when the AGC is inactive.
? // The fixed gain is also the initial gain when the device comes out of shutdown mode or when the AGC is disabled.
? // value 6 seems to work ok... based on datasheet. Where gain is from -28 (dB) to 30 (dB)
// Serial.println("Setting Fixed Gain");
? audioamp.setGain(-12); //-27 is ok? -12 is too high local stations arnt clipped...
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? ? // Compression Ratio: The relation between input and output voltage.
? // AGC can be TPA2016_AGC_OFF (no AGC) or
? //? TPA2016_AGC_2 (1:2 compression)
? //? TPA2016_AGC_4 (1:4 compression) * Datasheet - Voice
? //? TPA2016_AGC_8 (1:8 compression)
//? Serial.println("Setting AGC Compression");
? audioamp.setAGCCompression(TPA2016_AGC_8);
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? // Limiter Level: The value that sets the maximum allowed output amplitude.
//? Serial.println("Setting Limit Level");
? audioamp.setLimitLevelOn();
? // or turn off with?
? //audioamp.setLimitLevelOff();
? audioamp.setLimitLevel(30);? // range from 0 (-6.5dBv) to 31 (9dBV) (8.5dBv(30) as per datasheet)
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? //Maximum Gain: The gain at the lower end of the compression region
//? Serial.println("Setting AGC Max Gain (18-30db - (0-12)");
? audioamp.setAGCMaxGain(12);
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? /*
? ?*? ?For voice systems the attack time should be in the 2-ms region, with a hang time of about 0.3 sec,
? ?*? ?followed by a gradual recovery time of up to 1 sec.?
? ?*? ?http://www.qsl.net/va3iul/Files/Automatic_Gain_Control.pdf
? ?*
? ?*/
??
? // See Datasheet page 23 for value -> ms conversion table
//? Serial.println("Setting AGC Attack (0.1-6.7ms - (0-63))");
? audioamp.setAttackControl(3);
??
? // See Datasheet page 24 for value -> ms conversion table
//? Serial.println("Setting AGC Hold (0.0137-0.8631ms - (1-63))");
? audioamp.setHoldControl(0);
??
? // See Datasheet page 24 for value -> ms conversion table
//? Serial.println("Setting AGC Release (0.0137-0.8631ms - (0-63))");
? audioamp.setReleaseControl(4);
} |
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Also, need to add this new function to Adafuit library after the existing enableChannel function:
// Turn on/off Nosie Gate
void Adafruit_TPA2016::enableNoiseGate(boolean ng) {
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? uint8_t setup = read8(TPA2016_SETUP);
? if (ng)
? ? setup |= TPA2016_SETUP_NOISEGATE;
? else?
? ? setup &= ~TPA2016_SETUP_NOISEGATE;
??
? write8(TPA2016_SETUP, setup);
} |
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My Appologies.
In my haste I pasted in the wrong function, I will get the correct one tonight... I connected the board to the TDA side of the volume control, basically eliminating the TDA chip completely. Please be aware that the output from the TPA2016 is to be connected directly to the speaker, and NOT grounded at all, this is due to the fact that these outputs are Bridge Tied Load which means you must connect the speakers directly - do not try to connect these outputs to another amplifier! 73 and good luck. |
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in .h file:
void setNoiseGateThreshold(uint8_t thresh); in .cpp file void Adafruit_TPA2016::setNoiseGateThreshold(uint8_t thresh){ //Added by VK4PLN
if (thresh > 3) return; // max threshold is 3 (20mV)
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uint8_t agc = read8(TPA2016_AGCLIMIT);
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? agc &= ~(0x20);? // mask off bottom 5 bits
? agc |= thresh;? ? ? ? // set the limit level.
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? write8(TPA2016_AGCLIMIT, agc);
} 73 |
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Hi mike, I'll put the files up soon...
I did have the same issue with low audio. That is what the noise gate threshold is for, we want to set it very low(0) so that it lets even weak signals and static through... Then play with the gain setting in the software... I'll try put up a bit more details as to my exact setup, but you are on the right track. |
Nick VK4PP
Michael Monteith