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NI Digital System Development Board User Manual
USB UART Bridge (Serial Port)
The DSDB includes an FTDI FT2232HQ USB-UART bridge (attached to connector J13) that
lets you use PC applications to communicate with the board using standard Windows COM port
commands. Free USB-COM port drivers, available from www.ftdichip.com
www.ftdichip.com
under the
Virtual Com Port
or VCP heading, convert USB packets to UART/serial port data.
Serial port data is exchanged with the Zynq using a two-wire serial port (TXD/RXD). After the
drivers are installed, I/O commands can be used from the PC directed to the COM port to
produce serial data traffic on the Zynq pins. The port is tied to FPGA pins and can be used in
combination with the UART 1 or UART 0 controllers via EMIO.
Two on-board status LEDs provide visual feedback on traffic flowing through the port: the
transmit LED (LD10) and the receive LED (LD9). Signal names that imply direction are from
the point-of-view of the DTE (Data Terminal Equipment), in this case the PC.
The FT2232HQ is also used as the controller for the Digilent USB-JTAG circuitry, but the
USB-UART and USB-JTAG functions behave entirely independent of one another.
Programmers interested in using the UART functionality of the FT2232 within their design do
not need to worry about the JTAG circuitry interfering with the UART data transfers, and
vice-versa. The combination of these two features into a single device allows the DSDB to be
programmed and communicated with via UART from a computer attached with a single Micro
USB cable.
microSD Slot
The DSDB provides a microSD slot (J15) for non-volatile external memory storage as well as
booting the Zynq. The slot is wired to Bank 1/501 MIO[40-47], including Card Detect. On the
PS side peripheral SDIO 0 is mapped out to these pins and controls communication with the SD
card. The pinout can be seen in Table 6. The peripheral controller supports 1-bit and 4-bit SD
transfer modes, but does not support SPI mode. Based on the Zynq TRM, SDIO host mode is the
only mode supported.
Table 6.
microSD Pinout
Signal Name
Description
Zynq Pin
SD Slot Pin
SD_D0
Data[0]
MIO42
7
SD_D1
Data[1]
MIO43
8
SD_D2
Data[2]
MIO44
1
SD_D3
Data[3]
MIO45
2
SD_CCLK
Clock
MIO40
5
SD_CMD
Command
MIO41
3
SD_CD
Card Detect
MIO47
9