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Replace 16-bit read style with slower, but apparently more reliable 8-bit read style

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This commit is contained in:
Reed Nightingale 2020-05-05 20:36:03 -07:00
parent d282062eef
commit b3a7e34d1b
1 changed files with 22 additions and 22 deletions
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44
touch.cpp
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@ -28,6 +28,7 @@ constexpr uint16_t MEASURE_Z2 = START_COMMAND | POWER_ADC | CHANNEL_Z2;
constexpr uint8_t RAW_READ_TO_12BIT_VALUE_SHIFT = 3;//16 bits read, zero-padded, but the MSB of the 16 is where the "BUSY" signal is asserted, so only need to shift by 3 instead of 4
uint32_t msraw=0x80000000;
int16_t xraw=0, yraw=0, zraw=0;
constexpr uint8_t rotation = 1;
@ -48,6 +49,14 @@ int16_t touch_besttwoavg( int16_t x , int16_t y , int16_t z ) {
return (reta);
}
uint16_t touchReadChannel(uint8_t channel_command){
//We assume that SPI.beginTransaction has already been called, and CS is LOW
SPI.transfer(channel_command);//Throw away any bytes here
const uint16_t tmpH = SPI.transfer(0) & 0x7F;//Leading 0 (during "busy" signal), followed by bits 11-5
const uint16_t tmpL = SPI.transfer(0);//Bits 4-0, followed by 0s
return tmpH << 5 | tmpL >> 3;
}
void touch_update(){
zraw = 0;//Default value to report
@ -59,35 +68,26 @@ void touch_update(){
SPI.beginTransaction(spiSettingsTouch);
digitalWrite(PIN_TOUCH_CS, LOW);
//NOTE: SPI transfers are synchronous, but require setup!
// What happens here is that we first send a command to measure
// an axis, then send our next measure command while receiving
// the measurement requested previously, which is why it looks
// like we're "off by one" between the variable names and the
// commands being issued
SPI.transfer(MEASURE_Z1);
int16_t z1 = SPI.transfer16(MEASURE_Z2) >> RAW_READ_TO_12BIT_VALUE_SHIFT;
int32_t z = z1 + 4095;
int16_t z2 = SPI.transfer16(MEASURE_X) >> RAW_READ_TO_12BIT_VALUE_SHIFT;
z -= z2;
Serial.print(F("z1:"));Serial.print(z1);Serial.print(F(" z2:"));Serial.print(z2);Serial.print(F(" z:"));Serial.println(z);
int16_t z1 = touchReadChannel(MEASURE_Z1);//~0 when not pressed, increases with pressure
int32_t z = z1;
int16_t z2 = touchReadChannel(MEASURE_Z2);//~4095 when not pressed, decreases with pressure
z += (4095 - z2);
//Serial.print(F("z1:"));Serial.print(z1);Serial.print(F(" z2:"));Serial.print(z2);Serial.print(F(" z:"));Serial.println(z);
if (z < Z_THRESHOLD) {
SPI.transfer16(MEASURE_X & ~POWER_ADC_REF);//throw away the X measure so that we don't see it on the next check, and turn off the system
SPI.transfer16(0);
digitalWrite(PIN_TOUCH_CS, HIGH);
SPI.endTransaction();
return;
}
zraw = z;
SPI.transfer16(MEASURE_X); //throw away the first X measure, 1st is always noisy
// make 3 x-y measurements
int16_t data[6];
data[0] = SPI.transfer16(MEASURE_Y) >> RAW_READ_TO_12BIT_VALUE_SHIFT;
data[1] = SPI.transfer16(MEASURE_X) >> RAW_READ_TO_12BIT_VALUE_SHIFT; // make 3 x-y measurements
data[2] = SPI.transfer16(MEASURE_Y) >> RAW_READ_TO_12BIT_VALUE_SHIFT;
data[3] = SPI.transfer16(MEASURE_X) >> RAW_READ_TO_12BIT_VALUE_SHIFT;
data[4] = SPI.transfer16(MEASURE_Y) >> RAW_READ_TO_12BIT_VALUE_SHIFT;
data[5] = SPI.transfer16(0) >> RAW_READ_TO_12BIT_VALUE_SHIFT;
data[0] = touchReadChannel(MEASURE_X);
data[1] = touchReadChannel(MEASURE_Y);
data[2] = touchReadChannel(MEASURE_X);
data[3] = touchReadChannel(MEASURE_Y);
data[4] = touchReadChannel(MEASURE_X);
data[5] = touchReadChannel(MEASURE_Y & ~POWER_ADC_REF);//Turn off sensor
digitalWrite(PIN_TOUCH_CS, HIGH);
SPI.endTransaction();
@ -123,7 +123,7 @@ void initTouch(){
bool readTouch(Point *const touch_point_out){
touch_update();
Serial.print(F("readTouch found zraw of "));Serial.println(zraw);
//Serial.print(F("readTouch found zraw of "));Serial.println(zraw);
if (zraw >= Z_THRESHOLD) {
touch_point_out->x = xraw;
touch_point_out->y = yraw;