ESP32 reading DHT22 sensor in ULP coprocessor - sensors

Question

I´m trying to read a dht22 sensor in ulp deep sleep, and it´s not working, can perhaps someone tell me what I´m doing wrong?
I´m reimplementing the arduino-DHT library because it´s working in non ulp mode with my sensor, it looks like this:
digitalWrite(pin, LOW); // Send start signal
pinMode(pin, OUTPUT);
delayMicroseconds(800);
pinMode(pin, INPUT);
digitalWrite(pin, HIGH); // Switch bus to receive data
// We're going to read 83 edges:
// - First a FALLING, RISING, and FALLING edge for the start bit
// - Then 40 bits: RISING and then a FALLING edge per bit
// To keep our code simple, we accept any HIGH or LOW reading if it's max 85 usecs long
uint16_t rawHumidity = 0;
uint16_t rawTemperature = 0;
uint16_t data = 0;
for ( int8_t i = -3 ; i < 2 * 40; i++ ) {
byte age;
startTime = micros();
do {
age = (unsigned long)(micros() - startTime);
if ( age > 90 ) {
error = ERROR_TIMEOUT;
return;
}
}
while ( digitalRead(pin) == (i & 1) ? HIGH : LOW );
if ( i >= 0 && (i & 1) ) {
// Now we are being fed our 40 bits
data <<= 1;
// A zero max 30 usecs, a one at least 68 usecs.
if ( age > 30 ) {
data |= 1; // we got a one
}
}
switch ( i ) {
case 31:
rawHumidity = data;
break;
case 63:
rawTemperature = data;
data = 0;
break;
}
}
Looks simple enough :D, I tried the first part with this code, but it doesn´t work:
rtc_gpio_init(15);
rtc_gpio_set_direction(15, RTC_GPIO_MODE_INPUT_OUTPUT);
And in my ulp script file:
.set temp_humidity_sensor_pin, 13 // gpio 15 (adc 13)
send_start_signal:
/* disable hold on gpio 15 (data pin) */
WRITE_RTC_REG(RTC_IO_TOUCH_PAD3_REG, RTC_IO_TOUCH_PAD3_HOLD_S, 1, 0)
/* switch to output mode */
WRITE_RTC_REG(RTC_GPIO_OUT_W1TS_REG, RTC_GPIO_OUT_DATA_W1TS_S + temp_humidity_sensor_pin, 1, 1)
/* send start signal (LOW) */
WRITE_RTC_REG(RTC_GPIO_OUT_REG, RTC_GPIO_OUT_DATA_S + temp_humidity_sensor_pin, 1, 0)
/* pull low for 800 microseconds (8Mhz) */
wait 6400
/* switch to input mode */
WRITE_RTC_REG(RTC_GPIO_OUT_W1TC_REG, RTC_GPIO_OUT_DATA_W1TC_S + temp_humidity_sensor_pin, 1, 1)
/* switch bus to receive data (HIGH) */
WRITE_RTC_REG(RTC_GPIO_OUT_REG, RTC_GPIO_OUT_DATA_S + temp_humidity_sensor_pin, 1, 1)
wait_for_sensor_preparation_low:
READ_RTC_REG(RTC_GPIO_IN_REG, RTC_GPIO_IN_NEXT_S + temp_humidity_sensor_pin, 1)
and r0, r0, 1
jump wait_for_sensor_preparation_low, eq
wait_for_sensor_preparation_high:
READ_RTC_REG(RTC_GPIO_IN_REG, RTC_GPIO_IN_NEXT_S + temp_humidity_sensor_pin, 1)
and r0, r0, 0
jump wait_for_sensor_preparation_high, eq
jump wake_up // <-- never called :(
Any ideas?

Answer 1

Your "and r0, r0, 0" instruction (near the end) always sets r0 to zero (x & 0 == 0 by definition), which means the following jump instruction will loop forever. Remember that the "eq" flag doesn't really mean "equal". It means "zero". I think you want:
wait_for_sensor_preparation_low:
READ_RTC_REG(RTC_GPIO_IN_REG, RTC_GPIO_IN_NEXT_S + temp_humidity_sensor_pin, 1)
and r0, r0, 1
jump wait_for_sensor_preparation_high, eq
jump wait_for_sensor_preparation_low
wait_for_sensor_preparation_high:
READ_RTC_REG(RTC_GPIO_IN_REG, RTC_GPIO_IN_NEXT_S + temp_humidity_sensor_pin, 1)
and r0, r0, 1
jump wait_for_sensor_preparation_high, eq
By the way, I wrote a C compiler for the ULP, which should make your life easier. It's on https://github.com/jasonful/lcc