USB GPIO Modules

32 Channel USB Pluggable GPIO Module

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Numato Lab’s 32 Channel USB Pluggable GPIO Module is a great product for controlling electrical and electronic devices remotely from a PC or Mobile Device over USB link. Ease of use and wider operating system compatibility are the primary goals behind this product’s design. Built-in USB to serial conversion allows the module to be used, without any specific knowledge about USB. This simplicity allows use of off-the-shelf Terminal Emulation programs such as Tera term,  PuTTY for controlling the module with a simple set of human readable commands. For power users, this module can be controlled by writing programs in various programming languages.


  • 32 TTL (3.3V) compatible GPIOs
  • 7 analog inputs with 10-bit resolution (multiplexed with digital IOs)
  • USB interface with CDC support. As easy as using a serial port, no USB knowledge required
  • All IOs available on easy to plug headers
  • Can be powered from USB or external power supply
  • Can be controlled by using standard serial console applications or custom applications

Some of the possible uses of this module includes:

  • Home Automation
  • Lighting Control
  • Garden Equipment Control
  • Industrial Automation
  • Test Fixtures
  • DIY and Hobby

This product is compatible with the following operating systems:

  • Windows XP and later versions (Windows 7, 8/8.1, 10 and future versions)
  • Windows 7 Embedded and later
  • Linux
  • Mac OS X
  • Android
  • Or any other operating system that supports USB CDC devices.

And these are some of the languages that can be used for programming:

  • C/C++
  • Visual Basic (VB6, VB2008, VB2010 express and other editions)
  • Visual Basic for Applications (Microsoft Office VBA)
  • Perl
  • Python
  • JAVA
  • Android
  • Javascript (Node.js)
  • And many more…

This module has 32 on board General purpose I/Os multiplexed with 7 Analog Inputs.  The analog inputs (multiplexed with GPIOs) can be accessed over USB interface for extended functionality. When connected to PC, the module will appear as a serial port in Windows Device Manager (or a serial tty device in Linux and Mac).

Technical Specifications

Number of GPIOs32
Number of analog inputs (Multiplexed with GPIOs)7
Digital circuit power supply voltage (USB or external)5V
Maximum current drawn by digital circuitry300mA
IO Specifications
Maximum IO source current : IO8 – IO1525mA
Maximum IO source current: IO21 – IO318mA
Maximum IO source current : IO0 – IO7, IO16 – IO202mA
Maximum IO sink current : IO8 – IO1525mA
Maximum IO sink current : IO21 – IO318mA
Maximum IO sink current : IO0 – IO7, IO16 – IO202mA
GPIO input low voltage 0.15V
GPIO input high voltage 3.3V
GPIO output low voltage 0V
GPIO output high voltage 3.3V
ADC Specifications
Full scale range0 – VDDV
Reference voltageVDDV
Recommended Impedance of Analog Voltage Source2.5KΩ
Other Information
USB Vendor ID0x2A19
USB Product ID0x080A

* All parameters considered nominal. Numato Systems Pvt. Ltd. reserves the right to modify products without notice.

How to Use 32 Channel USB Pluggable GPIO Module

Using this product is very easy. The USB CDC interface allows this device to be used with most readily available serial terminal software such as Tera Term or HyperTerminal. Below shows some of the software for different operating systems.

  • Windows
    • PuTTY
    • HyperTerminal
    • Tera Term
  • Linux
    • GNU Screen
    • PuTTY
  • Mac OS X
    • Screen Command
    • CoolTerm
    • goSerial


Components/Tools Required

Along with the module, you may need the items in the list below for easy and fast installation.
1. USB A to B cable

Connection Details

  • Connect the device to a USB port on the host system
  • Install driver (Only needed for Windows. Driver available for download on the product page.)
  • Open the COM port corresponding to the device using a Serial Terminal software
  • Enter commands (Very similar to entering commands at DOS prompt or Bash prompt)
  • Optionally write a script or application to automate your task

Refer documentation “Driver Installation”

The module is connected to the PC through a USB Type B cable. The digital circuitry is powered from the USB.

An external +5V power is required only if the USB port is unable to supply enough current.

GPIO/Analog Inputs

The module has 32 General Purpose IO pins that can be used for various custom applications. Some of these pins can be used as Analog to Digital Converter inputs as well. All IO pins support 3.3V TTL signals and the ADC input range is 0 to +3.3V. The ADC can acquire analog signal at the resolution of 10 bits per sample. It is recommended to use a series resistor with the GPIO/ADC pins when interfacing with other circuits. A 470 Ohms series resistor is recommended for current limiting when connecting LED to a GPIO.

In contrast to GPIOs Analog inputs can read voltages at any level between 0 to 3.3V volts. It is recommended to use a series resistor to protect the input from stray voltages and spikes. The internal Analog to Digital converter supports 10 bits resolution which is adequate for most applications.

The table below summarizes the GPIO and Analog to Digital Converter input positions on the header P9.


The table below summarizes the GPIO and Analog to Digital Converter input positions on the header P10.


The table below summarizes the GPIO and Analog to Digital Converter input positions on the header P5.


The table below summarizes the GPIO and Analog to Digital Converter input positions on the header P8.


Sending Commands

One of the most powerful features of this module is the simple easy to use command set it supports. This command set hides the complex USB protocol and gives a very simple interface to access the features of the module. The following sections give details of the command set and how to use the command set.

The Commands Set

This product supports a very simple command set that is designed to be less cryptic and easy to use manually (using serial terminal emulation programs) or through a program written in many supported languages.

List of currently supported commands.

1vernoneverReturns firmware version
2idgetId getReads Module ID
set xxxxxxxxid set 12345678Assign ID to the module
3gpioset xxx
clear xxx
gpio set 000
gpio clear 000
Control the GPIOs
read xxxgpio read 000Read GPIO Input status
status xxxgpio status 000Read GPIO status
readallgpio readallRead all GPIO status at a time
writeall xxxxxxxxgpio writeall ffffffffControl all GPIOs at a time
iomask xxxxxxxxgpio iomask ffffffffControl GPIOs mask status
iodir xxxxxxxxgpio iodir 00000000Control GPIOs direction
notify on
notify off
gpio notify on
gpio notify off
Control Notify feature
notify getgpio notify getRead Notify Status
poweron xxxxxxxx xxxxxxxxgpio poweron 00000000 ffffffffControl GPIO Power-On IO direction & status respectively
4adcread xxxadc read 000Read Analog to Digital Converter input value
5infoNoneinfoReturns GPIO Power-On Direction & Status

The table below has more detailed information about available commands.

1ververReturns firmware version.
2idid getReads the module ID.
id set xxxxxxxxAssign an 8-digit ID to the module, where ‘x’ can be any alphanumeric character.
3gpiogpio set xxxSet GPIO ‘xxx’ output status to high.

gpio set 000 – Sets IO0 to high state
xxx can be 000 – 031
gpio clear xxxSets GPIO ‘xxx’ output status to low.

gpio clear 000 – Sets IO0 to low state
xxx can be 000 – 031
gpio read xxxRead the input status present at ‘xxx’.

gpio read 007 – Read input status of IO7 and print either ‘1’ or ‘0’ depending on the status
xxx can be 000 – 031
gpio status xxxRead the GPIO status present at ‘xxx’ without changing the GPIO to inputs.

gpio status 007 – Read status of IO7 and print either ‘1’ or ‘0’ depending on the status
xxx = 000 to 031
gpio iomask xxxxxxxxMasks/Unmasks all GPIOs in a single operation.
gpio iomask ffff0000 – Masks and/or unmasks GPIO at each bit position according to the bits of the specified hexadecimal value.
0 – To mask the GPIO & 1 – To unmask the GPIO.
‘ffff0000’ – 1111 1111 1111 1111 0000 0000 0000 0000: Masks GPIOs 0 – 15 & unmasks GPIOs 16 - 31.
gpio iodir xxxxxxxxSets direction of all GPIOs as Input/output mode in a single operation.
gpio iodir 0000540f – Sets GPIOs as input/output at each bit position according to the bits of the specified hexadecimal value.
0 – To set the GPIO as output mode & 1 – To set the GPIO as input mode.
‘0000540f’ – 0000 0000 0000 0000 0101 0100 0000 1111:
Sets GPIO 0,1,2,3,10,12 & 13 as input mode
Sets GPIO 4,5,6,7,8,9,11,13,15,16-30 & 31 as output mode.
gpio readallRead status of all GPIOs in single operation.
gpio readall – Read all GPIO status and print xxxxxxxx.
xxxxxxxx is a hexadecimal value, with binary 1 at positions for GPIOs in HIGH and 0 for GPIOs in LOW state.
gpio writeall xxxxxxxxControl all GPIOs in single operation.
Gpio writeall ffff67a4 – Sets and clears GPIO at each bit position according to the bits of the specified hexadecimal value.
0 – To clear the GPIO & 1 – To set the GPIO
‘ffff67a4’ – 1111 1111 1111 1111 0110 0111 1010 0100:
Sets GPIO 2,5,7,8,9,10,13-14,16-30 & 31
Clears GPIO 0,1,4,6,11,12 & 15.
Refer Understanding readall/writeall commands for GPIO Modules to know more.
gpio notify onThis command enables the gpio input change notification. When the gpio notify feature is enabled, changes to the input pins will be detected and a notification is sent to the host.
To use notify feature on a GPIO, the GPIO must be set to input mode by using “gpio iodir” command.
The GPIO change notification is sent to the host is in the below format.

If GPIO change notification is “FFFFFFFE FFFFFFFF FFFFFFFF”, then
1. Current IODIR value is FFFFFFFF which means all GPIOs are set to input mode.
2. Previous GPIO values are FFFFFFFF.
3. Current GPIO values are FFFFFFFE.
The GPIO 0 value is changed from logic 1 to 0. This change triggered the device to send this notification.
gpio notify offThis command disables the gpio input change notification feature.
gpio notify getReturns whether Notify feature is enabled or disabled.
gpio poweron xxxxxxxx xxxxxxxxThis command is to control Power-On GPIO Direction and status in a single operation.
gpio poweron ffff0000 000011c5 – Sets GPIOs IO direction and status respectively at each bit position according to the bits of the specified hexadecimal value.
IO direction: 0 – To set the GPIO as output mode & 1 – To set the GPIO as input mode.
IO status: 0 - To clear the GPIO & 1 - To set the GPIO.
‘ffff0000 000011c5’- (1111 1111 1111 1111 0000 0000 0000 0000) (0000 0000 0000 0000 0001 0001 1100 0101):
GPIOs 0-15 are set to output mode & GPIOs 16-31 are set as input mode.
GPIO 0,2,6,7,8 & 12 are set to High
GPIO 1,3,4,5,9-11,13-14 & 15 are set to Low.
4adcadc read xxxReads the analog voltage present at the ADC input mentioned. “xxx” stands for the number of ADC input. The response will be a number that ranges from 0 – 1023. Please see examples below.
adc read 000 – Reads analog input 0
adc read 004 – Reads analog input 4
xxx can be 000 to 006
5infoinfoReturns GPIO Power-On Direction & Status.

Accessing the module

32 Channel USB Pluggable GPIO Module allows to communicate through any of the Serial Terminal Emulator Software

using simple easy to use commands mentioned in the command set above.

Refer documentation “Sending Commands to the Numato Lab USB Modules” to know more.

Additional Information

Analog to Digital Converters (ADCs)

7 GPIOs on board do support Analog to Digital Conversion. There is no special command required to execute to switch between analog and digital mode. Executing “adc” command will set the GPIO to analog mode and executing “gpio” command will set the GPIO back to digital mode on the fly. Resolution of the ADC is 10 bits unless otherwise noted. The input voltage range of the ADC is 0 – VDD (this product uses 3.3V power supply, so the range will be 0 – 3.3V). The result will be returned as a number starting at zero and ending at 1023. Zero indicates zero volts at the ADC input and 1023 indicates VDD (3.3V for this product) at ADC input.

GPIO with Switches

USBGpio Switch connection diagramIt is possible to read the position of a switch that is connected to a GPIO. A SPST or SPDT switch is recommended to use with GPIOs. Push switches do maintain the contacts closed only for a very short time so using them is discouraged. The fundamental idea of using a switch with GPIO is to have the switch cause a voltage level change at the GPIO pin when pressed. Usually this is achieved by using an external pull-up resistor along with the switch. The pull up resistor is connected between the GPIO and VDD and the switch is connected between the GPIO and ground. When the switch is not pressed, the pull-up resistor will cause the GPIO to stay at VDD voltage level. When the switch is pressed, the GPIO is short circuited to ground and stays at zero voltage. This change in voltage and thus the position of the switch can be read using “gpio read” command.

Frequently Asked Questions (FAQs)

Q. What are the serial parameters I need to use when communicating with this board?
A. Since this module uses USB as the underlying transport mechanism, most of the serial parameters do not affect the communication. You can leave all parameters to any legal value (Eg: 2400, 4800, 9600 etc… for baud rate) except Flow control. Flow control needs to be set to “None”.

Q. Where do I find driver for this product?
A. Visit and navigate to the product page. There will be a link to download windows driver. Linux does not require driver installation since in most cases they are shipped with the driver pre-installed.

Q. Why there is no .sys or .exe file in the Windows driver package I downloaded?
A. This product uses USB CDC driver binary which is already present on Windows. All Windows versions (with the exception of Embedded Editions) has this driver binary installed by default. The .inf and .cat files present in the zip file helps Windows identify the device properly and associate appropriate driver (.sys) to the device

Q. Does this product work with Linux?
A. Yes, this product works with Linux. Please see more details on how to use this product with Linux elsewhere in this document.

Q. Does this product work with Mac OSX?
A. Yes, this product works with Mac OSX. Please see more details on how to use this product with Mac elsewhere in this document.

Q. What are the serial terminal software that this product work with?
A. This product works with a lot of different Serial Terminal software. Some examples can be found elsewhere in this document. Different Serial Terminal software are written by different developers with different purposes in mind. So you may encounter some software that may not work with this product. But usually alternatives are available in most if not all cases.

Q. The GPIO looses its previously set value when trying to read the status. Why it is so?
A. When a gpio is to output a value (high/low), that particular GPIO is put to output mode. When you are trying to read the GPIO, it needs to be put in input mode. In input mode, the GPIO will go to high impedance state and thus looses the previously set value.

Q. I’m using x language for programming. How do I find out if this language can be used to program and control the GPIO module?
A. Find out if the language of interest supports some kind of APIs/Functions/Components for serial communication. If it does, most likely you should be able to use that language with this module.

Q. What is the connector marked as ICSP on this module?
A. This connector is used to program the on-board microcontroller. This connector is primarily intended for factory use.

Q. I need a customized version of this product, can Numato do the customization for me?
A. Yes, we can definitely do customization but there may be minimum order requirements depending on the level of customization required. Please write to [email protected] for a quote.

Q. Where can I buy this product?
A. All Numato products can be ordered directly from our web store We accept major credit cards and Paypal and ship to almost all countries with a few exceptions. We do have distributors in many countries where you can place your order. Please find the current list of distributors at

Mechanical Dimensions

Header On Top :

Header On Bottom :

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