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MPR121 12-Channel Capacitive Touch Sensor Module

Nim wrapper for the MPR121 capacitive touch sensor.

The MPR121 provides 12 individual capacitive touch sensor inputs with automatic baseline tracking and configurable touch/release thresholds. Perfect for building custom touch interfaces and musical instruments.

Features:

12 capacitive touch sensor channels
Automatic baseline tracking
Configurable touch and release thresholds
Filtered and baseline data readback
I2C interface only
Touch status register for reading all channels at once

Example:

import nimphea
import nimphea/dev/mpr121

var sensor: Mpr121I2C
var config: Mpr121Config

# Configure I2C transport
config.transport_config.dev_addr = MPR121_I2CADDR_DEFAULT
config.transport_config.periph = I2C_PERIPH_1
config.transport_config.speed = I2C_400KHZ
config.transport_config.scl = seed.GetPin(11)  # PB8
config.transport_config.sda = seed.GetPin(12)  # PB9
config.touch_threshold = 12
config.release_threshold = 6

if sensor.init(config) == MPR121_OK:
  while true:
    let touched = sensor.touched()
    for i in 0..11:
      if (touched and (1 shl i)) != 0:
        # Channel i is touched
        discard

Imports

nimphea, i2c

Types

Mpr121Config {.importcpp: "daisy::Mpr121I2C::Config", bycopy.} = object transport_config* {.importcpp: "transport_config".}: Mpr121I2CTransportConfig touch_threshold* {.importcpp: "touch_threshold".}: uint8 release_threshold* {.importcpp: "release_threshold".}: uint8: MPR121 device configuration Source Edit
Mpr121I2C {.importcpp: "daisy::Mpr121I2C", bycopy.} = object: MPR121 sensor with I2C transport Source Edit
Mpr121I2CTransport {.importcpp: "daisy::Mpr121I2CTransport", bycopy.} = object: I2C transport for MPR121 Source Edit
Mpr121I2CTransportConfig {.importcpp: "daisy::Mpr121I2CTransport::Config", bycopy.} = object periph* {.importcpp: "periph".}: I2CPeripheral speed* {.importcpp: "speed".}: I2CSpeed scl* {.importcpp: "scl".}: Pin sda* {.importcpp: "sda".}: Pin mode* {.importcpp: "mode".}: I2CMode dev_addr* {.importcpp: "dev_addr".}: uint8: I2C transport configuration Source Edit
Mpr121Result {.importcpp: "daisy::Mpr121<daisy::Mpr121I2CTransport>::Result", size: 4.} = enum MPR121_OK = 0, ## Success MPR121_ERR = 1 ## Error: Operation result Source Edit

Consts

MPR121_I2CADDR_DEFAULT = 0x5A'u8: Default I2C address Source Edit
MPR121_RELEASE_THRESHOLD_DEFAULT = 6'u8: Default release threshold value Source Edit
MPR121_TOUCH_THRESHOLD_DEFAULT = 12'u8: Default touch threshold value Source Edit

Procs

proc baselineData(this: var Mpr121I2C; channel: uint8): uint16 {. importcpp: "#.BaselineData(#)", header: "dev/mpr121.h", ...raises: [], tags: [], forbids: [].}: Read the baseline value for a channel

Parameters:

channel - Channel number (0-12)

Returns: Baseline data value
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proc filteredData(this: var Mpr121I2C; channel: uint8): uint16 {. importcpp: "#.FilteredData(#)", header: "dev/mpr121.h", ...raises: [], tags: [], forbids: [].}: Read the filtered data from a channel

The ADC raw data is filtered through 3 levels of digital filtering to remove high and low frequency noise.

Parameters:

channel - Channel number (0-12)

Returns: 10-bit filtered reading
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proc init(this: var Mpr121I2C; config: Mpr121Config): Mpr121Result {. importcpp: "#.Init(#)", header: "dev/mpr121.h", ...raises: [], tags: [], forbids: [].}: Initialize the MPR121 sensor

Parameters:

config - Configuration struct with transport and threshold settings

Returns: MPR121_OK on success, MPR121_ERR on failure
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proc initMpr121Config(): Mpr121Config {.constructor, importcpp: "daisy::Mpr121I2C::Config(@)", header: "dev/mpr121.h".}: Initialize device config with defaults Source Edit
proc initMpr121I2CTransportConfig(): Mpr121I2CTransportConfig {.constructor, importcpp: "daisy::Mpr121I2CTransport::Config(@)", header: "dev/mpr121.h".}: Initialize I2C transport config with defaults Source Edit
proc readRegister8(this: var Mpr121I2C; reg: uint8): uint8 {. importcpp: "#.ReadRegister8(#)", header: "dev/mpr121.h", ...raises: [], tags: [], forbids: [].}: Read an 8-bit register value

Parameters:

reg - Register address to read

Returns: 8-bit register value
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proc readRegister16(this: var Mpr121I2C; reg: uint8): uint16 {. importcpp: "#.ReadRegister16(#)", header: "dev/mpr121.h", ...raises: [], tags: [], forbids: [].}: Read a 16-bit register value

Parameters:

reg - Register address to read

Returns: 16-bit register value
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proc setThresholds(this: var Mpr121I2C; touch: uint8; release: uint8) {. importcpp: "#.SetThresholds(#, #)", header: "dev/mpr121.h", ...raises: [], tags: [], forbids: [].}: Set touch and release thresholds for all channels

Parameters:

touch - Touch threshold value (0-255)

release - Release threshold value (0-255)

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proc touched(this: var Mpr121I2C): uint16 {.importcpp: "#.Touched()", header: "dev/mpr121.h", ...raises: [], tags: [], forbids: [].}: Read the touch status of all 13 channels

Each bit represents the touch status of one channel. Bit 0 = channel 0, bit 1 = channel 1, etc.

Returns: 12-bit value with touch status (bit set = touched)
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proc writeRegister(this: var Mpr121I2C; reg: uint8; value: uint8) {. importcpp: "#.WriteRegister(#, #)", header: "dev/mpr121.h", ...raises: [], tags: [], forbids: [].}: Write an 8-bit value to a register

Automatically handles stop mode requirements.

Parameters:

reg - Register address to write

value - Value to write

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