MAXREFDES72 : Quick Start Guide Required Equipment Device with a modern web browser and the ability to write to an external USB drive Microcontroller board with Arduino UNO R3-compatible socket headers MAXREFDES72 board MAX3232PMB1 or other Pmod-compatible peripheral module, available here Overview This Quick Start Guide explains how to configure the MAXREFDES72 to map functions from Arduino headers to a Pmod connector. The MAXREFDES72 is capable of arbitrary pin mapping with a few restrictions. In general, the board is configured by 2 writing to the MAX14661 multiplexer over the I C bus. As the Figure 2 shows, 8 Arduino digital GPIO are connected to the Pmod connector through level shifters and each of these 8 signals are also connected to the multiplexer. The 8 digital signals were chosen so that the Arduino Uno R3 SPI signals are connected for 2 the Pmod Type 2 and to avoid the I C and UART signals at the Arduino headers. For Type 1 (GPIO) and Type 2 (SPI), no configuration is necessary. To implement 2 Type 3, Type 4, I C, or other custom pin mappings that 2 need access to I C, UART, or other real time functions such as PWM, configure the multiplexer to route the signals to the appropriate pins. Figure 1 Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000 2014 Maxim Integrated Products, Inc. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. +3.3V IOREF IOREF IOREF DS3231M 32K SCL SCL SCL VCC SDA SDA SDA SQW BAT GND GND RST GND IOREF IOREF SCL D15 SDA D14 +3.3V IOREF NC IOREF VL VCC GND +3.3V PA4 D13 NC D13 PA3 D12 IOREF D12 MAX14611 PA2 D11 RST D11 PA1 D10 +3.3V D10 +3.3V D9 +5V TS GND D9 D8 GND 6 5 4 3 2 1 A D8 GND 6 5 4 3 2 1 B VIN VL VCC PB4 D7 D7 PB3 D6 D6 MAX14611 PB2 D5 A0 TP0 D5 PB1 D4 A1 TP1 D4 D3 A2 TP2 TS GND D3 D2 A3 TP3 D2 D1 A4 TP4 D1 D0 A5 TP5 D0 SCL I2C SDA A1 SD A0 Figure 2 The MAX14661 is a 16:2 matrix multiplexer with all 16 of the Arduino digital IO connected to the 16 port side of the matrix switch. The COM pins on the 2 port side of the matrix switch are used internally for routing, but are also connected to test points and can be used for debug. To route the UART to the Pmod connector, turn on the A switch connected to the RX (AB01) and the A switch connected to the desired Pmod pin (AB12), then turn on the B switch connected to TX (AB02) and the B switch connected to the desired Pmod pin (AB13). Any of the 8 pins that are not connected to the Pmod connector directly can be connected to any of the 8 Pmod connector pins and the only limitation is that only two independent signals can be routed like this at the same time. The multiplexer is programmable and the two channels can be time multiplexed if necessary. An example demonstrating how to do this with the mbed platform is described in the Included Files and Procedure sections. In the included example, the microcontroller is only used to configure the MAX14661. The RS232 transceiver is actually being connected to the UART that is the virtual com port on the USB interface. The UART inside the microcontroller needs to be disabled. The flexibility of the MAXREFDES72 adapter allows the Rx and Tx to be swapped to connect the Pmod to the UART inside the microcontroller or to the USB virtual com port. Be careful to check how these signals are connected on the platform you have selected. See Appendix C: mbed Enabled Board Compatibility for some of the known compatibility issues. Included Files MAX14661.cpp MAX14661.h MAX3232 DEMO.cpp AB16 AB15 AB14 AB13 AB12 AB11 AB10 COMB AB09 AB08 COMA AB07 AB06 AB05 AB04 AB03 AB02 AB01