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Gives the SN76489 its proper dividers and personalities.

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This commit is contained in:
Thomas Harte
2018-02-28 22:36:03 -05:00
parent 83f73c3f02
commit 7890506b16
3 changed files with 45 additions and 27 deletions
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Components/SN76489/SN76489.cpp
+19 -6
View File
@@ -12,7 +12,7 @@
using namespace TI;
SN76489::SN76489(Concurrency::DeferringAsyncTaskQueue &task_queue) : task_queue_(task_queue) {
SN76489::SN76489(Personality personality, Concurrency::DeferringAsyncTaskQueue &task_queue) : task_queue_(task_queue) {
// Build a volume table.
double multiplier = pow(10.0, -0.1);
double volume = 8191.0f;
@@ -22,6 +22,21 @@ SN76489::SN76489(Concurrency::DeferringAsyncTaskQueue &task_queue) : task_queue_
}
volumes_[15] = 0;
evaluate_output_volume();
switch(personality) {
case Personality::SN76494:
master_divider_period_ = 2;
shifter_is_16bit_ = false;
break;
case Personality::SN76489:
master_divider_period_ = 16;
shifter_is_16bit_ = false;
break;
case Personality::SMS:
master_divider_period_ = 16;
shifter_is_16bit_ = true;
break;
}
}
void SN76489::set_register(uint8_t value) {
@@ -72,10 +87,8 @@ void SN76489::evaluate_output_volume() {
}
void SN76489::get_samples(std::size_t number_of_samples, std::int16_t *target) {
// For now: assume a divide by eight.
std::size_t c = 0;
while((master_divider_&7) && c < number_of_samples) {
while((master_divider_& (master_divider_period_ - 1)) && c < number_of_samples) {
target[c] = output_volume_;
master_divider_++;
c++;
@@ -124,12 +137,12 @@ void SN76489::get_samples(std::size_t number_of_samples, std::int16_t *target) {
evaluate_output_volume();
for(int ic = 0; ic < 8 && c < number_of_samples; ic++) {
for(int ic = 0; ic < master_divider_period_ && c < number_of_samples; ++ic) {
target[c] = output_volume_;
c++;
master_divider_++;
}
}
master_divider_ &= 7;
master_divider_ &= (master_divider_period_ - 1);
}
Components/SN76489/SN76489.hpp
+10 -3
View File
@@ -16,8 +16,14 @@ namespace TI {
class SN76489: public Outputs::Speaker::SampleSource {
public:
enum class Personality {
SN76489,
SN76494,
SMS
};
/// Creates a new SN76489.
SN76489(Concurrency::DeferringAsyncTaskQueue &task_queue);
SN76489(Personality personality, Concurrency::DeferringAsyncTaskQueue &task_queue);
/// Writes a new value to the SN76489.
void set_register(uint8_t value);
@@ -26,8 +32,9 @@ class SN76489: public Outputs::Speaker::SampleSource {
void get_samples(std::size_t number_of_samples, std::int16_t *target);
private:
std::size_t master_divider_ = 0;
int16_t output_volume_ = 0;;
int master_divider_ = 0;
int master_divider_period_ = 16;
int16_t output_volume_ = 0;
void evaluate_output_volume();
int volumes_[16];