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This article describes the CHESTER-X0 four-channel I/O extension module. Two variants are available:

  • CHESTER-X0A including 5.0V boost converter
  • CHESTER-X0B without 5.0V boost converter

Module Overview

Each channel can be used for these applications:

  • Digital input and output
  • Analog input and output
  • Voltage input 0 - 26 V*
  • Current loop 4 - 20 mA
  • Dry contact input
  • NPN and PNP input
  • Power output
    • X0A with boost converter: 5 V
    • X0B w/o boost converter: standard 3.0 V (VDD solder bridge) or on request V+ battery rail (V+ solder bridge)

* CHESTER-M main board has on Ax and Bx terminal block pins TVS protection that starts to protect GPIO above 28 V. Theoretically you can measure higher voltage than 26 V but the protection distorts measurements or you need to request or remove these TVS.

Channel Schematic Diagram

Depending on the application these configuration options are available for each channel:

  • Enable pull-up resistor 330 kΩ (PUX)
  • Enable pull-down resistor 249 Ω (PDX)
  • Enable voltage divider (gain 1/11) (100 kΩ, 10 kΩ) (CLX)
  • Enable 5V boost converter (CHESTER-X0A only) (ONX)

This picture show the electric circuit of each channel:

Configuration Table

The configuration depends on the application.

Signals PUx, CLx, PDx, ONx refers to the schematic above. Green tick ✅ means that the I2C GPIO expander or X0 sends a logic high signal to this configuration signal. However, this is just to understand the modes. You only need to know which mode is set in the ctr_x0_set_mode table column.

ApplicationPUxCLxPDxONxSDK ctr_x0_set_mode
Analog input 0-26 VCTR_X0_MODE_AI_INPUT
Current loop 4-20 mACTR_X0_MODE_CL_INPUT
Analog output 0-VDDCTR_X0_MODE_DEFAULT
Digital inputCTR_X0_MODE_DEFAULT
Digital outputCTR_X0_MODE_DEFAULT

CHESTER Pin Configuration Diagram

Pin Configuration and Functions

PositionSignal NameSignal Description
1VDDSystem VDD rail 3.0 V
2CH1Channel 1
3GNDSystem ground signal
4CH2Channel 2
5CH3Channel 3
6GNDSystem ground signal
7CH4Channel 4
8+VSystem positive rail (*)

*Note: The system positive rail voltage depends on CHESTER power supply option.

Schematic diagram

A schematic diagram is useful if you program low-level hardware-related code or if you're just curious about how the system is designed.

Module Drawing