DesignSpark.Pmod¶

Python library to support using Pmods with a Raspberry Pi and the DesignSpark Pmod HAT.

Features include:

Simple interfaces for supported Pmods
Checking that Pmod and port capabilities match
Checking for port usage conflicts
Usage examples

Supported Pmods¶

The following Pmods are currently supported:

PmodAD1 12-bit ADC
PmodHB3 2A H-bridge driver
PmodISNS20 20A Current Sensor
PmodMIC3 MEMS Microphone Module
PmodOLEDrgb 96x64 RGB OLED Display ¹
PmodTC1 K Type Thermocouple Module with Wire

¹ Builds on the excellent luma.oled and luma.core libraries from Richard Hull and contributors.

Installation¶

DesignSpark.Pmod can be installed from PyPi using pip. See the documentation for details.

Documentation¶

Installation and API documentation, along with examples, can be found at:

http://designspark-pmod.readthedocs.io

For Pmod HAT documentation, including the reference manual and schematic, see:

https://reference.digilentinc.com/reference/add-ons/pmod-hat/start

Table of Contents¶

Installation¶

This guide assumes that you are running Raspbian Stretch.

First enable SPI:

pi@raspberrypi:~$ sudo raspi-config

Selecting:

Option 5 - Interfacing
P4 - SPI
Enable → YES

Then exit raspi-config.

Next update the package lists:

pi@raspberrypi:~$ sudo apt-get update

Then install the Raspbian dependencies:

pi@raspberrypi:~$ sudo apt-get install python-pip python-dev libfreetype6-dev libjpeg-dev build-essential

Finally, install DesignSpark.Pmod and dependencies from PyPi:

pi@raspberrypi:~$ sudo pip install designspark.pmod

Pmod Information¶

Details of currently supported Pmods can be found below.

AD1¶

The Digilent Pmod AD1 (Revision G) is a two channel 12-bit analog-to-digital converter that features Analog Devices’ AD7476A. With a sampling rate of up to 1 million samples per second, this Pmod™ is capable of excelling in even the most demanding audio applications.

Features:

Two channel 12-bit analog-to-digital converter
Simultaneous A/D conversion at up to one MSa per channel
Two 2-pole Sallen-Key anti-alias filters
Small PCB size for flexible designs 0.95 in × 0.8 in (2.4 cm × 2.0 cm)
6-pin Pmod port with GPIO interface

Note

Only a single channel (A1) is supported at present due to the way that SPI is configured.

HB3¶

The Pmod HB3 utilizes a full H-Bridge circuit to allow users to drive DC motors from the system board. Two external pins are provided on the Pmod for sensor feedback on the DC motor, if desired.

Features:

2A H-bridge circuit
Drive a DC motor with operation voltage up to 12V
Screw terminal blocks for connection to the motor
Separate header for external motor feedback
6-pin Pmod port with GPIO interface

ISNS20¶

The Digilent Pmod ISNS20 (Revision A) is a small current sense module with a digital SPI interface. The board combines an Allegro ACS722 Hall Effect current sensor with a 12-bit analog-to-digital converter from Texas Instruments. The Pmod ISNS20 is quick, accurate, and easy to use for a variety of applications.

Features:

High accuracy current sensor
Measure current with 120Hz/20kHz/80kHz jumper selections
±20A DC or AC input
Accurate to within ±2%
12-bit ADC
6-pin Pmod port with SPI interface
Follows Digilent Pmod Interface Specification Type 2

MIC3¶

The Digilent Pmod MIC3 (Revision A) is small microphone module with a digital interface. With a Knowles Acoustics SPA2410LR5H-B MEMs microphone and Texas Instrument’s ADCS7476 12-bit Analog-to-Digital Converter, you can capture your audio inputs with ease.

Features:

MEMS Microphone module with digital interface
Transform audio inputs with 12-bit A/D converter
Adjust incoming volume with on-board potentiometer
Up to 1 MSPS of data
6-pin Pmod port with SPI interface
Follows Digilent Pmod Interface Specification Type 2

OLEDrgb¶

The Digilent Pmod OLEDrgb (Revision B) is an organic RGB LED module with a 96×64 pixel display capable of 16-bit color resolution.

Features:

96×64 pixel RGB OLED screen
0.8“ x 0.5” graphical display
16-bit color resolution
Two low-power display shutdown modes
12-pin Pmod connector with SPI interface

TC1¶

The Digilent Pmod TC1 (Revision A) is a cold-junction thermocouple-to-digital converter module designed for a classic K-Type thermocouple wire. With Maxim Integrated’s MAX31855, this module reports the measured temperature in 14-bits with 0.25°C resolution.

Features:

K-type thermocouple-to-digital converter
Wide temperature range of -73°C to 482°C with provided wire
±2°C accuracy from -200°C to 700°C
14-bit with 0.25°C resolution
Cold-junction temperature compensation
6-pin Pmod port with SPI interface
Follows Digilent Pmod Interface Specification Type 2

Basic Examples¶

AD1¶

12-bit analog-to-digital converter.

Print volts out to the terminal¶

Read ADC channel A1, print the voltage measured out to the terminal, sleep for 0.8s and repeat.

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright (c) 2017 RS Components Ltd
# SPDX-License-Identifier: MIT License

"""
Read ADC channel A1 and print volts out.
"""

from DesignSpark.Pmod.HAT import createPmod
import time

if __name__ == '__main__':
    adc = createPmod('PmodAD1','JBA')
    time.sleep(0.1)
    
    try:
        while True:
            volts = adc.readA1Volts()
            print(volts)
            #val = adc.readA1()
            #print(val)
            time.sleep(0.8)
    except KeyboardInterrupt:
        pass
    finally:
        adc.cleanup()

Requirements

PmodAD1 module connected to port JBA
A voltage source connected to ADC channel A1

HB3¶

2A H-bridge circuit for DC motor drive up to 12V.

Spin motor¶

This example:

Spins the motor forwards for 20 seconds
Commands the motor to stop and pauses for 2 seconds
Spins the motor in reverse for 20 seconds
Commands the motor to stop and pauses for 2 seconds
Ramps up the speed across 100 steps in the forward direction
Ramps down the speed across 100 steps in the forward direction
Ramps up speed across 100 steps in the reverse direction
Ramps down the speed across 100 steps in the reverse direction
Loops back to (1)

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright (c) 2017 RS Components Ltd
# SPDX-License-Identifier: MIT License

"""
Spin motor forwards then backwards.
Ramp speed up and then down in forward direction.
Ramp speed up and then down in reverse direction.
"""

from DesignSpark.Pmod.HAT import createPmod
import time

if __name__ == '__main__':

    motor = createPmod('PmodHB3','JAA')

    try:
        while True:
        
            print('fwd')
            motor.forward(20)
            time.sleep(2)
            motor.stop()
            time.sleep(2)
            print('rev')
            motor.reverse(20)
            time.sleep(1)
            motor.stop()
            time.sleep(2)
            
            
            print ('ramp up fwd')
            for i in range(100):
                motor.forward(i)
                time.sleep(.1)
            
            print ('ramp down fwd')
            for i in range(100):
                motor.forward(100-i)
                time.sleep(.1)
                
            motor.stop()
            time.sleep(2)
            
            print ('ramp up rev')
            for i in range(100):
                motor.reverse(i)
                time.sleep(.1)
            
            print ('ramp down rev')
            for i in range(100):
                motor.reverse(100-i)
                time.sleep(.1)
        
    except KeyboardInterrupt:
        pass
    
    finally:
        motor.cleanup() 
    
    
    

Requirements

PmodHB3 module connected to port JAA
DC motor
Motor power supply

ISNS20¶

±20A DC or AC input, high accuracy current sensor.

Print milliamps out to the terminal¶

Read the current sense module, print the milliamps out to the terminal, sleep for 0.8s and repeat.

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright (c) 2017 RS Components Ltd
# SPDX-License-Identifier: MIT License

"""
Read current and print out milliamps.
"""

from DesignSpark.Pmod.HAT import createPmod
import time

if __name__ == '__main__':
    
    isens = createPmod('PmodISNS20','JBA')
    time.sleep(0.1)
    
    try:
        while True:
            mA = isens.readMilliAmps()
            print(mA)
            time.sleep(0.8)
    except KeyboardInterrupt:
        pass
    finally:
        isens.cleanup()

Requirements

PmodISNS20 module connected to port JBA
Suitable current source, e.g. a power supply and load

MIC3¶

Knowles Acoustics SPA2410LR5H-B MEMs microphone and Texas Instrument’s ADCS7476 12-bit Analog-to-Digital Converter.

Display mic level¶

Print a continous sound level reading out to the terminal.

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright (c) 2017 RS Components Ltd
# SPDX-License-Identifier: MIT License

"""
Print a continous sound level reading out.
"""

from DesignSpark.Pmod.HAT import createPmod
import time

s = ':'
lut = [s]
for i in range(128):
    s+=':'
    lut.append(s)

if __name__ == '__main__':
    
    mic = createPmod('PmodMIC3','JBA')
    time.sleep(0.1)
    
    try:
        while True:
            int = mic.readIntegerValue()
            #print(int)
            print(lut[int>>5])
            snd = mic.readPhysicalValue()
            #print(snd)
            
            #time.sleep(0.01)
    except KeyboardInterrupt:
        pass
    finally:
        mic.cleanup()

Requirements

PmodMIC3 module connected to port JBA

OLEDrgb¶

Organic RGB LED module with a 96×64 pixel display capable of 16-bit color resolution.

Display text in a bounding box¶

Display the text “Hello, World!” in a bounding box.

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright (c) 2017 RS Components Ltd
# SPDX-License-Identifier: MIT License

"""
Display Hello, World! in bounding box.
"""

from DesignSpark.Pmod.HAT import createPmod
from luma.core.render import canvas
from luma.oled.device import ssd1331

if __name__ == '__main__':
    try:
        oled = createPmod('PmodOLEDrgb','JA')
        device = oled.getDevice()
        
        with canvas(device) as draw:
            draw.rectangle(device.bounding_box, outline="white", fill="black")
            draw.text((16,20), "Hello, World!", fill="white")
    
        while True:
            pass
    except KeyboardInterrupt:
        pass
    finally:
        oled.cleanup()

Luma.Core & Luma.OLED API: luma.core.render.canvas, luma.oled.device.ssd1331.

Requirements

PmodOLEDrgb connected to port JA

PmodTC1¶

A cold-junction thermocouple-to-digital converter module designed for a classic K-Type thermocouple wire. Features a temperature range of -73°C to 482°C with provided wire.

Print celsius out to the terminal¶

Print the celsius reading out to the terminal, sleep for 0.8s and repeat.

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright (c) 2017 RS Components Ltd
# SPDX-License-Identifier: MIT License

"""
Print the celsius reading out.
"""

from DesignSpark.Pmod.HAT import createPmod
import time

if __name__ == '__main__':
    
    therm = createPmod('PmodTC1','JBA')
    time.sleep(0.1)
    
    try:
        while True:
            cel = therm.readCelcius()
            print(cel)
            #intn = therm.readInternal()
            #print(intn)
            time.sleep(0.8)
    except KeyboardInterrupt:
        pass
    finally:
        therm.cleanup()

Requirements

PmodTC1 module connected to port JBA

API¶

`DesignSpark.Pmod.AD1`¶

Interface for PmodAD1 module (AD7476A).

Note

Only a single channel (A1) is supported at present due to the way that SPI is configured.

class DesignSpark.Pmod.AD1.PmodAD1(DSPMod6)[source]¶

cleanup()[source]¶

readA1()[source]¶

readA1Volts()[source]¶

`DesignSpark.Pmod.Error`¶

exception DesignSpark.Pmod.Error.Error[source]¶

Bases: exceptions.Exception

Base class for exceptions in this library.

exception DesignSpark.Pmod.Error.incorrectModuleName[source]¶

Bases: DesignSpark.Pmod.Error.Error

Exception raised when the module name given does not exist in the module map.

exception DesignSpark.Pmod.Error.incorrectPortName[source]¶

Bases: DesignSpark.Pmod.Error.Error

Exception raised when the port name given does not exist in the port map.

exception DesignSpark.Pmod.Error.portCapabilityConflict[source]¶

Bases: DesignSpark.Pmod.Error.Error

Exception raised when the port is already using shared GPIO pins.

exception DesignSpark.Pmod.Error.portCapabilitySupport[source]¶

Bases: DesignSpark.Pmod.Error.Error

Exception raised when a port does not support the module type.

exception DesignSpark.Pmod.Error.portInUse[source]¶

Bases: DesignSpark.Pmod.Error.Error

Exception raised when the port is already assigned.

`DesignSpark.Pmod.HAT`¶

Manages Pmod HAT port resources, enforcing correct usage and avoiding conflicts.

class DesignSpark.Pmod.HAT.DSPMod12(_portName)[source]¶

inUse()[source]¶

setUseModule(moduleName)[source]¶

class DesignSpark.Pmod.HAT.DSPMod6(_portName)[source]¶

inUse()[source]¶

setUseModule(moduleName)[source]¶

DesignSpark.Pmod.HAT.createPmod(moduleName, portName)[source]¶

`DesignSpark.Pmod.HB3`¶

Interface for PmodHB3 module.

class DesignSpark.Pmod.HB3.PmodHB3(DSPMod6)[source]¶

changeFrequency(freq)[source]¶

cleanup()[source]¶

forward(duty)[source]¶

reverse(duty)[source]¶

stop()[source]¶

`DesignSpark.Pmod.ISNS20`¶

Interface for PmodISNS20 module (ADC7476 + Allegro ACS722).

class DesignSpark.Pmod.ISNS20.PmodISNS20(DSPMod6)[source]¶

cleanup()[source]¶

readAmps()[source]¶

readMilliAmps()[source]¶

`DesignSpark.Pmod.MIC3`¶

Interface for PmodMIC3 (ADCS7476 + Knowles Acoustics SPA2410LR5H-B).

class DesignSpark.Pmod.MIC3.PmodMIC3(DSPMod6)[source]¶

MIC3_NO_BITS = 12¶

cleanup()[source]¶

dReference = 3.3¶

readIntegerValue()[source]¶

readPhysicalValue()[source]¶

`DesignSpark.Pmod.OLEDrgb`¶

Interface for PmodOLEDrgb module (ssd1331).

Note

Depends on luma.oled and luma.core.

class DesignSpark.Pmod.OLEDrgb.PmodOLEDrgb(DSPMod12)[source]¶

cleanup()[source]¶

getDevice()[source]¶

powerOff()[source]¶

powerOn()[source]¶

`DesignSpark.Pmod.TC1`¶

Interface for PmodTC1 module (MAX31855).

class DesignSpark.Pmod.TC1.PmodTC1(DSPMod6)[source]¶

cleanup()[source]¶

readCelcius()[source]¶

readError()[source]¶

readFarenheit()[source]¶

readInternal()[source]¶

Change log¶

Version	Description	Date
0.2.0	Tidied up names, added documentation and examples	28/11/17
0.1.0	Initial version	26/11/17

The MIT License (MIT)¶

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.