mirror of
https://github.com/whowechina/chu_pico.git
synced 2024-09-24 02:58:20 +02:00
170 lines
7.2 KiB
C
170 lines
7.2 KiB
C
/*
|
|
* Copyright (c) 2021-2022 Antonio González
|
|
*
|
|
* SPDX-License-Identifier: BSD-3-Clause
|
|
*/
|
|
|
|
#include "mpr121.h"
|
|
|
|
void mpr121_init(i2c_inst_t *i2c_port, uint8_t i2c_addr,
|
|
mpr121_sensor_t *sensor) {
|
|
sensor->i2c_port = i2c_port;
|
|
sensor->i2c_addr = i2c_addr;
|
|
|
|
// Enter stop mode by setting ELEPROX_EN and ELE_EN bits to zero.
|
|
// This is needed because register write operations can only take
|
|
// place in stop mode.
|
|
mpr121_write(MPR121_ELECTRODE_CONFIG_REG, 0x00, sensor);
|
|
|
|
// Writing 0x80 (SOFT_RESET) with 0x63 asserts soft reset.
|
|
mpr121_write(MPR121_SOFT_RESET_REG, 0x63, sensor);
|
|
|
|
// == Capacitance sensing settings (AN2889), Filtering and =========
|
|
// timing settings (AN3890)
|
|
|
|
// These settings are configured in two registers: the Filter and
|
|
// Global CDC CDT Configuration registers (0x5C, 0x5D).
|
|
//
|
|
// Charge-discharge current (CDC) and charge-discharge time (CDT)
|
|
// can be configured globally or on a per-electrode basis. Here,
|
|
// The global CDC and CDT values are set to their defaults, and then
|
|
// these values are overriden by independently configuring each
|
|
// electrode (auto-configuration).
|
|
|
|
// Filter/global CDC configuration register (0x5C)
|
|
//
|
|
// First filter iterations (FFI), bits 7-6. Number of samples taken
|
|
// as input to the first level of filtering. Default is 0b00 (sets
|
|
// samples taken to 6)
|
|
//
|
|
// Charge-discharge current (CDC), bits 5-0. Sets the value of
|
|
// charge-discharge current applied to the electrode. Max is 63 µA
|
|
// in 1 µA steps. Default is 0b010000 (16 µA)
|
|
//
|
|
// AFE configuration register default, 0b00010000 = 0x10
|
|
mpr121_write(MPR121_AFE_CONFIG_REG, 0x10, sensor);
|
|
|
|
// Filter/global CDC configuration register (0x5D)
|
|
//
|
|
// Charge discharge time (CDT), bits 7-5. Selects the global value
|
|
// of charge time applied to electrode. The maximum is 32 μs,
|
|
// programmable as 2^(n-2) μs. Default is 0b001 (time is set to
|
|
// 0.5 µs)
|
|
//
|
|
// Second filter iterations (SFI), bits 4-3. Selects the number of
|
|
// samples taken for the second level filter. Default is 0b00
|
|
// (number of samples is set to 4)
|
|
//
|
|
// Electrode sample interval (ESI), bits 2-0. Controls the sampling
|
|
// rate of the device. The maximum is 128 ms, programmable to 2^n
|
|
// ms. Decrease this value for better response time, increase to
|
|
// save power. Default is 0b100 (period set to 16 ms).
|
|
//
|
|
// Filter configuration register default, 0b00100100 = 0x24
|
|
// I do not need power saving features but I want fast responses,
|
|
// so I set this to 0x20.
|
|
mpr121_write(MPR121_FILTER_CONFIG_REG, 0x20, sensor);
|
|
|
|
// Auto-configuration
|
|
//
|
|
// Sets automatically charge current (CDC) and time (CDT) values for
|
|
// each electrode.
|
|
//
|
|
// Autoconfig USL register: the upper limit for the
|
|
// auto-configuration. This value (and those that follow below)
|
|
// were calculated based on Vdd = 3.3 V and following the equations
|
|
// in NXP Application Note AN3889.
|
|
// USL = 201 = 0xC9
|
|
mpr121_write(MPR121_AUTOCONFIG_USL_REG, 0xC9, sensor);
|
|
|
|
// Autoconfig target level register: the target level for the
|
|
// auto-configuration baseline search.
|
|
// TL = 181 = 0xB5
|
|
mpr121_write(MPR121_AUTOCONFIG_TARGET_REG, 0xB5, sensor);
|
|
|
|
// Autoconfig LSL register: the lower limit for the
|
|
// auto-configuration.
|
|
// LSL = 131 = 0x83
|
|
mpr121_write(MPR121_AUTOCONFIG_LSL_REG, 0x83, sensor);
|
|
|
|
// Autoconfiguration control register. Default value is 0b00001011 =
|
|
// 0x0B, where:
|
|
//
|
|
// First filter iterations (FFI), bits 7-6. Must be the same value
|
|
// of FFI as in register MPR121_AFE_CONFIG_REG (0x5C) above;
|
|
// default is 0b00.
|
|
//
|
|
// Retry, bits 5-4. Default is disabled, 0b00.
|
|
//
|
|
// Baseline value adjust (BVA), bits 3-2. This value must be the
|
|
// same as the CL (calibration lock) value in the Electrode
|
|
// Configuration Register, below, i.e. 0b10.
|
|
//
|
|
// Automatic Reconfiguration Enable (ARE), bit 1. Default is 0b1,
|
|
// enabled.
|
|
//
|
|
// Automatic Reconfiguration Enable (ACE), bit 0. Default is 0b1,
|
|
// enabled.
|
|
mpr121_write(MPR121_AUTOCONFIG_CONTROL_0_REG, 0x0B, sensor);
|
|
|
|
// == Baseline system (AN3891) =====================================
|
|
|
|
// Maximum Half Delta (MHD): Determines the largest magnitude of
|
|
// variation to pass through the baseline filter. The range of the
|
|
// effective value is 1~63.
|
|
mpr121_write(MPR121_MAX_HALF_DELTA_RISING_REG, 0x01, sensor);
|
|
mpr121_write(MPR121_MAX_HALF_DELTA_FALLING_REG, 0x01, sensor);
|
|
|
|
// Noise Half Delta (NHD): Determines the incremental change when
|
|
// non-noise drift is detected. The range of the effective value is
|
|
// 1~63.
|
|
mpr121_write(MPR121_NOISE_HALF_DELTA_RISING_REG, 0x01, sensor);
|
|
mpr121_write(MPR121_NOISE_HALF_DELTA_FALLING_REG, 0x01, sensor);
|
|
mpr121_write(MPR121_NOISE_HALF_DELTA_TOUCHED_REG, 0x01, sensor);
|
|
|
|
// Noise Count Limit (NCL): Determines the number of samples
|
|
// consecutively greater than the Max Half Delta value. This is
|
|
// necessary to determine that it is not noise. The range of the
|
|
// effective value is 0~255.
|
|
mpr121_write(MPR121_NOISE_COUNT_LIMIT_RISING_REG, 0x00, sensor);
|
|
mpr121_write(MPR121_NOISE_COUNT_LIMIT_FALLING_REG, 0xFF, sensor);
|
|
mpr121_write(MPR121_NOISE_COUNT_LIMIT_TOUCHED_REG, 0x00, sensor);
|
|
|
|
// Filter Delay Count Limit (FDL): Determines the operation rate of
|
|
// the filter. A larger count limit means the filter delay is
|
|
// operating more slowly. The range of the effective value is 0~255.
|
|
mpr121_write(MPR121_FILTER_DELAY_COUNT_RISING_REG, 0x00, sensor);
|
|
mpr121_write(MPR121_FILTER_DELAY_COUNT_FALLING_REG, 0x02, sensor);
|
|
mpr121_write(MPR121_FILTER_DELAY_COUNT_TOUCHED_REG, 0x00, sensor);
|
|
|
|
// == Debounce and thresholds (AN3892) =============================
|
|
|
|
// Debounce. Value range for each is 0~7.
|
|
// Bits 2-0, debounce touch (DT).
|
|
// Bits 6-4, debounce release (DR).
|
|
mpr121_write(MPR121_DEBOUNCE_REG, 0x00, sensor);
|
|
|
|
// Touch and release threshold values for all electrodes.
|
|
for (uint8_t i=0; i<12; i++) {
|
|
mpr121_write(MPR121_TOUCH_THRESHOLD_REG + i * 2, 0x0F, sensor);
|
|
mpr121_write(MPR121_RELEASE_THRESHOLD_REG + i * 2, 0x0A, sensor);
|
|
}
|
|
|
|
// Electrode Configuration Register (ECR, 0x5E). This must be the
|
|
// last register to write to because setting ELEPROX_EN and/or
|
|
// ELE_EN to non-zero puts the sensor in Run Mode.
|
|
//
|
|
// Calibration lock (CL), bits 7-6. The default on reset is 0b00
|
|
// (CL enabled). Here I set this instead to 0b10 because this
|
|
// enables baseline tracking with initial baseline value loaded
|
|
// with the 5 high bits of the first electrode data value, which
|
|
// makes the sensor stabilise sooner. Note that ths value must
|
|
// match BVA bits in the Auto-configure Control Register above.
|
|
//
|
|
// Proximity enable (ELEPROX_EN), bits 5-4. Default, 0b00
|
|
// (proximity detection disabled).
|
|
//
|
|
// Electrode enabled (ELE_EN), bits 3-0. Default, 0b1100 (enable
|
|
// all 12 electrodes).
|
|
mpr121_write(MPR121_ELECTRODE_CONFIG_REG, 0x8C, sensor);
|
|
} |