Connection of USB-to-JTAG Interface Board to MAX1441 Application Circuit

introduction

The MAX1441 is a signal-conditioning integrated circuit (IC) that supports capacitive proximity-sensor designs for automotive passive keyless entry (PKE) and other systems. The MAX1441 has two independent contact/proximity detection channels, and a complete suite of components to support the IC includes:

• Integrated development environment MAX-IDE, providing assembly, compilation, user interface and flash programmer functions.
• Example code and typical application firmware.
• The MAX1441EVSYS, a fully tested evaluation (EV) system, includes interface hardware, application circuit, and a touchpad with two touch pads.

JTAG interface for production test systems

Production test systems need to use interface boards to program and test end products, including the MAX1441. There are three options:

Develop a custom interface board or purchase a JTAG interface board from a third party and confirm that it works with the MAX1441.

Modify the jumper settings based on the MAX1441EVKIT control circuit, then remove the MAX1441 from the EV kit. Refer to the MAX1441EVKIT data sheet to configure the MAX1441EVKIT board.

Use the USB to JTAG interface board MAXQUSBJTAG-KIT provided by Maxim.

As long as the circuit works properly, all three methods are feasible. The first method, customizing the interface board or purchasing the interface board from a third party, requires the user to participate in a lot of work and spend a lot of time. The user needs to verify whether the interface board is compatible with the MAX1441 and ensure reliable communication; the second method is more mature, because each evaluation board of Maxim is factory-verified before leaving the factory, and the operation and interface functions of the MAX1441 are strictly tested. However, this method requires changing the settings of the evaluation board, and each test system requires a dedicated evaluation board; the third method uses the MAXQUSBJTAG-KIT interface board, which is very simple and easy to operate because the interface board has been verified to ensure reliable communication with the MAX1441.

This article details the connection between the MAXQUSBJTAG-KIT interface board and the MAX1441 typical application circuit. The relevant information given here is applicable to any circuit board and device that conforms to the JTAG communication protocol, including microprocessors.

Interface Connections

Figure 1 shows an application circuit that connects the MAX1441 to the JTAG interface of the MAXQUSBJTAG-KIT board. Note: In the schematic, the JTAG lines require pull-up resistors, which are part of the application circuit. Usually, the pull-up resistors are part of the test system and do not need to be repeated on the application board.

Figure 1. Connecting the MAX1441 application circuit to the MAXQUSBJTAG-KIT board's JTAG interface.

Figure 2 shows the configuration: an application board with a test socket; a touch pad connected to the MAX1441's second-channel input; and the MAXQUSBJTAG-KIT board connected to a computer (not shown). Note that the application board has a test socket for engineering purposes and does not need to be installed in the actual application circuit.

Figure 2. MAX1441 application board and MAXQUSBJTAG-KIT connection configuration.

Build the setup and run the entire system as shown in Figure 2. First, refer to the MAX1441EVSYS data sheet to install the relevant software; then use the MAX-IDE application in the MAX1441EVSYS software package as the user interface to program the MAX1441; finally, refer to the MAX1441 data sheet and other supporting documents, including the MAXQ® Family User's Guide or the User's Guide for MAXQ microcontrollers, to operate the device and define registers.