Nuts and Volts - October 2010

overridden with a value of 10 decimal. The VOS_xxxx definitions were gleaned from the vos.h header file. We entered the NUMBER_OF_DEVICES value when we coded the application header file DesignCycle-App.h.

This would be a good time to set up the Vinculum-II clocking. As you might imagine, the toolchain API has a call for that:

vos_set_clock_frequency(VOS_48MHZ_CLOCK_
FREQUENCY);

As you can see in Schematic 1, the 48 MHz clock is derived from a 12 MHz crystal and the Vinculum-II’s 4x PLL. In a previous Design Cycle Vinculum-II discussion, we took a detailed look at a helper program called the VNC2 IOMux Config utility which is part of the Vinculum-II toolchain package. If you had the opportunity to join in on that conversation, you’ll recall that the VNC2 IOMux Config utility is used to configure the GPIO subsystem. An added feature of this utility is that it writes the GPIO configuration code for us. Well, we need some UART I/O code for sure and if we want to add some status LEDs to the mix, we should go ahead and lay out some output I/O pins to support them, as well. Here’s what the VNC2 IOMux Config utility produced according to my idea of where things should go:

// GPIO port A bit 1 to pin 12 – LED3 ON
// EVAL BOARD
vos_iomux_define_output(12,IOMUX_OUT_GPIO_PORT_
A_1);

THE DESIGN CYCLE

// GPIO port A bit 2 to pin 13 – LED4 ON
// EVAL BOARD
vos_iomux_define_output(13,IOMUX_OUT_GPIO_PORT_
A_2);
// GPIO port A bit 5 to pin 29 – LED5 ON EVAL
// BOARD
vos_iomux_define_output(29,IOMUX_OUT_GPIO_PORT_
A_5);
// GPIO port A bit 6 to pin 31 – LED6 ON EVAL
// BOARD
vos_iomux_define_output(31,IOMUX_OUT_GPIO_PORT_
A_6);
// UART to V2EVAL board pins
vos_iomux_define_output(39,IOMUX_OUT_UART_TXD);
 //UART Tx
vos_iomux_define_input(40,IOMUX_IN_UART_RXD);
 //UART Rx
vos_iomux_define_output(41,IOMUX_OUT_UART_RTS_N);
 //UART RTS#
vos_iomux_define_input(42,IOMUX_IN_UART_CTS_N);
 //UART CTS#

I’m sure you’re wondering why I chose these particular I/O pins and LED identifiers. The cat is let out of the bag in the comments area of the code generated by the VNC2 IOMux Config utility. I guess it would be a good idea to add some LED definitions to our application header code:

#define LED0 0x02  //LED3 ON EVAL BOARD
#define LED1 0x04  //LED4 ON EVAL BOARD
#define LED2 0x20  //LED5 ON EVAL BOARD
#define LED3 0x40  //LED6 ON EVAL BOARD