hugely simplified version of the touchio.TouchIn.get_raw_reading code (adafruit/circuitpython#1048)

1 files changed, 15 insertions, 99 deletions

diff --git a/ports/nrf/common-hal/touchio/TouchIn.c b/ports/nrf/common-hal/touchio/TouchIn.c
index b2d61f548..6b8f17c99 100644
--- a/ports/nrf/common-hal/touchio/TouchIn.c
+++ b/ports/nrf/common-hal/touchio/TouchIn.c
@@ -37,120 +37,36 @@
 #include "supervisor/shared/translate.h"
 
 #include "nrf.h"
-#include "nrfx/hal/nrf_saadc.h"
 
-#include "tick.h"
-
-bool touch_enabled = false;
-
-#define CHANNEL_NO 0
 #define N_SAMPLES 10
-#define K_FACTOR 100000000L
-
-static uint16_t process_samples(nrf_saadc_value_t samples[], int n_samples) {
-    // XXX sort of like a least squares fit here, with the assumption
-    // that the timing ('x') is stable (thus we suspend interrupts while
-    // taking these measurements)
-
-    int32_t sumy = 0;
-    int32_t sumxy = 0;
-
-    for (int i = 0; i < N_SAMPLES; i++) {
-        sumy += samples[i];
-        sumxy += i*samples[i];
-    }
-
-    // we don't really care about the units, and so we can cut out a 
-    // whole bunch of stuff which is based only on N_SAMPLES, eg:
-    // n, sum(x), sum(x^2) and sum(x)^2 terms.  This leaves only:
-
-    int16_t m = (N_SAMPLES - 1) * sumy / 2 - sumxy;
-
-    // m is proportional to the charge rate of the capacitor which is 
-    // in reciprocal proportion to the actual capacitance.  
-    return (uint16_t)(K_FACTOR / m);
-}
+#define TIMEOUT_US 10000
 
 static uint16_t get_raw_reading(touchio_touchin_obj_t *self) {
 
-    nrf_saadc_value_t samples[N_SAMPLES];
-
-    // Configure analog input.
-    // XXX analogio.AnalogIn and this class both use SAADC channel 0 
-    // all the time and never any other channel.  This seems a bit 
-    // silly.
-
-    const nrf_saadc_channel_config_t config = {
-        .resistor_p = NRF_SAADC_RESISTOR_DISABLED,
-        .resistor_n = NRF_SAADC_RESISTOR_DISABLED,
-        .gain = NRF_SAADC_GAIN1_6,
-        .reference = NRF_SAADC_REFERENCE_INTERNAL,
-        .acq_time = NRF_SAADC_ACQTIME_3US,
-        .mode = NRF_SAADC_MODE_SINGLE_ENDED,
-        .burst = NRF_SAADC_BURST_DISABLED,
-        .pin_p = NRF_SAADC_INPUT_VDD,
-        .pin_n = NRF_SAADC_INPUT_VDD,
-    };
-
-    nrf_saadc_resolution_set(NRF_SAADC_RESOLUTION_14BIT);
-    nrf_saadc_oversample_set(NRF_SAADC_OVERSAMPLE_DISABLED);
-    nrf_saadc_enable();
+    uint16_t ticks = 0;
 
-    for (uint32_t i = 0; i < NRF_SAADC_CHANNEL_COUNT; i++)
-        nrf_saadc_channel_input_set(i, NRF_SAADC_INPUT_DISABLED, NRF_SAADC_INPUT_DISABLED);
+    for (uint16_t i = 0; i < N_SAMPLES; i++) {
+        // set pad to digital output high for 10us to charge it
 
-    nrf_saadc_channel_init(CHANNEL_NO, &config);
-    nrf_saadc_buffer_init(samples, N_SAMPLES);
+        nrf_gpio_cfg_output(self->pin->number);
+        nrf_gpio_pin_set(self->pin->number);
+        mp_hal_delay_us(10);
 
-    // set pad to digital output high for 10us to charge it
+        // set pad back to an input and take some samples
 
-    nrf_gpio_cfg_output(self->pin->number);
-    nrf_gpio_pin_set(self->pin->number);
+        nrf_gpio_cfg_input(self->pin->number, NRF_GPIO_PIN_NOPULL);
 
-    mp_hal_delay_us(10);
-
-    // set pad back to an input and take some samples
-    // IRQs are suspended to make sure our samples are at fixed times.
-
-     __disable_irq();
-
-    nrf_saadc_channel_input_set(CHANNEL_NO, self->pin->adc_channel, self->pin->adc_channel);
- 
-    nrf_saadc_task_trigger(NRF_SAADC_TASK_START);
-    while (nrf_saadc_event_check(NRF_SAADC_EVENT_STARTED) == 0);
-    nrf_saadc_event_clear(NRF_SAADC_EVENT_STARTED);
-
-    // XXX surely there's a better way? PPI?
-    for (uint32_t i = 0; i < N_SAMPLES; i++) {
-        nrf_saadc_task_trigger(NRF_SAADC_TASK_SAMPLE);
-        while (nrf_saadc_event_check(NRF_SAADC_EVENT_DONE) == 0);
-        nrf_saadc_event_clear(NRF_SAADC_EVENT_DONE);
+        while(nrf_gpio_pin_read(self->pin->number)) {
+            if (ticks >= TIMEOUT_US) return TIMEOUT_US;
+            ticks++;
+            mp_hal_delay_us(1);
+        }
     }
-
-    __enable_irq();
-
-    nrf_saadc_task_trigger(NRF_SAADC_TASK_STOP);
-    while (nrf_saadc_event_check(NRF_SAADC_EVENT_STOPPED) == 0);
-    nrf_saadc_event_clear(NRF_SAADC_EVENT_STOPPED);
-
-    // turn off SAADC & set output pin low (to minimize leakage currents)
-
-    nrf_gpio_pin_clear(self->pin->number);
-
-    nrf_saadc_channel_input_set(CHANNEL_NO, NRF_SAADC_INPUT_DISABLED, NRF_SAADC_INPUT_DISABLED);
-    nrf_saadc_disable();
-
-    nrf_gpio_cfg_output(self->pin->number);
-
-    return process_samples(samples, N_SAMPLES);
-
+    return ticks;
 }
 
 void common_hal_touchio_touchin_construct(touchio_touchin_obj_t* self,
         const mcu_pin_obj_t *pin) {
-    if (!pin->adc_channel) {
-        mp_raise_ValueError(translate("Invalid pin"));
-    }
     self->pin = pin;
     claim_pin(pin);
 }