Circuit Example: TWX-0001

TWX-0001 circuit diagram (pdf)

This is a circuit example when using TWE-001/001 STRONG. The circuit contains the RS232C interface, UART (common to JTAG) I/O, temperature/humidity sensor, button, LED, and power source.

*This circuit can also be used as the jig for writing firmware. Writing uses UART0 and the circuit employs level conversion to RS-232C. However, in case there is the UART-USB cable, UART0 can be drawn in accordance with the cable specifications.

Description of Parts

Power

This switches the power source according to how the jumper pin (JP1) is connected.

• Connecting 1 and 2 supplies 3V3 via the regulator (3.3V) to VDD.
• Connecting 2 and 3 supplies power from dry cells (2.0V to 3.6V using two alkaline dry cells).

Connector

This is the receiving connector for TWE-001/001 STRONG.

• The Reset button connects the pull-up resister R1 with the ceramic capacitor C1.
• The Program button connects the pull-up resistor with the capacitor as required.
  The following is the procedure for transitioning to the program mode:
  - Cancel reset (or power ON) while SPIMISO is low.
  - Keep the state for around 100 ms.
  - Set SPIMISO high (or open).
  The unit does not work if kept low.
  
• Make sure to connect SSZ (7) and SSM (16). These are the chip select pins to boot from the flash memory incorporated in the wireless module.
  *They are left open on the wireless module to allow them to boot up from the flash memory externally connected by SPI.

RS232C (UART0)

This is the circuit for communication with external devices using UART0.

3V3 supplied from the regulator is used as the power source. This is because ADM3202 has the standard voltage of 3.3 to 5.0 [V] and is not suitable for use where two dry cells are used.

The signal lines of ADM3202 and to the wireless module can be disconnected by the jumper for the purpose of disconnecting the circuit if, for instance, this RS232C circuit is not used. Leaving the circuit connected could cause current to flow from the IO signal line of the wireless module to the ADM3202 pin.

TX/RX will be available by connecting the jumpers [1-2] and [3-4], and CTS/RTC by connecting the jumpers [5-6] and [7-8].

LED and Switch

SW1, SW2, D1 and D2 employ the same wiring as that for the Evaluation and Development Kit.

Temperature and Humidity Sensor

The sensor employs the same wiring as that incorporated into the Evaluation and Development Kit.

JTAG/UART1

This is the wiring for the use of the UART1 or JTAG debugger. The use of a 2.54mm pin header allows you to use the same UART-USB cable as that for the Evaluation and Development Kit.

Disconnect the pin from the NC section of Pin 7 to avoid misconnection.

ADC1

TOCOS' GF063P (B202 [2kΩ] potentiometer is connected to ADC1.

Voltage to the potentiometer is supplied from the digital IO. Make sure to read the source voltage at the same time as reading ADC1 since both the digital IO and VCC have almost the same voltage. Also, the voltage has been divided according to the voltage range readable by ADC.

Processing of Unused Pins

• We recommend that analog pins be "open".
• We recommend that digital pins be open (pull-up settings also available internally) or pull-up (10k to 100kΩ).
• SWP pins are the WP pins for the M25P40 flash of the SPI flash, which can be either pull-up or pull-down. See the M25P40 data sheet for details.