Datasheet
MAX9259 Evaluation Kit
Evaluates: MAX9259
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the specified device register. Read Register reads the
specified device register and reports the results into the
Interface History window. Devices that are not register-
based (such as the MAX7324) are supported by Send
Data (no register) and Receive Data (no register).
User-supplied devices requiring other interface proto-
cols must use Raw TX byte codes to communicate.
Note that in bypass mode, raw data is passed to the
user-supplied slave device directly without modification.
Detailed Description of Hardware
The MAX9259 EV kit provides a proven layout for
the MAX9259. On-board level translators, S/PDIF-to-
I
2
S audio, and an easy-to-use USB-PC connection are
included on the EV kit.
The MAX9259 EV kit board layout is divided into four
principal sections.
From header H1 to connector J1 are the support compo-
nents specific to the MAX9259. On-board LDO regulator
U2 powers the AVDD, DVDD, and IOVDD supplies from
VIN. Jumper JU9 optionally connects VIN to the link
cable, powering the remote EV kit board.
Below header H1, the board layout has three sections:
microcontroller (U10–U14), I
2
C slave device (U15), and
audio (U20–U25). The microcontroller and I
2
C slave
device sections are identical on the MAX9259 and
MAX9260 EV kits.
The audio section of the MAX9259 EV kit contains
S/PDIF-to-I
2
S audio converter circuits (U20–U25), which
can be disabled by JU210 for applications already hav-
ing I
2
S audio.
The audio section of the MAX9260 EV kit contains I
2
S-
to-audio DAC circuits (U20, U21) and a Class D stereo
power amplifier (U25). The audio DAC circuits are similar
to the MAX9850 EV kit, and the power amplifier circuit is
similar to the MAX9701 EV kit.
User-Supplied Interface
To use the MAX9259 EV kit with a user-supplied inter-
face, first cut the PCB traces at jumpers JU141 and
JU142. Next, apply your own TX/SCL signal at the U1
side of JU141 and RX/SDA at the U1 side of JU142.
Refer to the MAX9259/MAX9260 IC data sheet for details
about UART protocol for base mode, write data format,
read data format, selecting base mode or bypass mode,
and selecting UART or I
2
C slave device.
User-Supplied Power Supply
The MAX9259 and MAX9260 EV kits are powered com-
pletely from the USB port by default. The 5V USB bus
power is supplied to the remote EV kit over the link cable
by default. Jumper JU10 powers the link cable (VBUS)
from the 5V USB supply, and jumper JU9 connects
VBUS to the VIN power supply.
To provide external power to each EV kit’s VIN, and
still power both microcontrollers from USB, remove the
shunt from jumper JU9, but leave the shunt at jumper
JU10 installed. VBUS carries the USB 5V bus power to
the remote EV kit board, but external user-supplied VIN
supplies are required to power the MAX9259 and the
MAX9260.
To provide different power supplies to DVDD, AVDD, and
IOVDD, remove the shunts from jumpers JU21, JU22,
and JU23, and apply external user-supplied power at the
DVDD, AVDD, and IOVDD oval pads.
The I
2
S audio link demonstration requires both MAX9259
EV kit and MAX9260 EV kit microcontrollers (U12) to be
powered, otherwise the on-board S/PDIF-to-I
2
S con-
verter or the I
2
S audio DAC does not initialize.
Detailed Description of Firmware
The DS89C450 microcontroller (U12) runs custom firm-
ware, which ensures that no breaks occur within regis-
ter read/write commands. The firmware records 9-bit,
even-parity data received from the USB interface while
RTS is set, and plays back the 9-bit data with 1.5 stop
bits timing when RTS is cleared. Data received from the
MAX9259 is relayed to USB immediately.
The audio chips are initialized by an I
2
C command
sequence sent by the firmware when the microcon-
troller is reset. The same firmware runs on both the
MAX9259 and MAX9260 EV kit boards, so this initializa-
tion sequence covers both the S/PDIF-to-I
2
S converter
and the MAX9850 I
2
S stereo audio DAC. Pressing switch
SW122 resets the microcontroller, resending the audio
I
2
C initialization commands.
The firmware also supports a small set of commands,
available when RTS is clear. Since all register read/
write requests are sent with RTS set, there is no conflict
between register data and firmware commands. These
firmware commands are issued automatically by the
MAX9259 EV kit software GUI. The following information
is provided for reference only.
Firmware command “?” prints the firmware version ban-
ner message and brief command list.
Firmware command “B” changes the baud rate by
changing the internal TH1 baud-rate divisor. Refer to
firmware help command “?” for details. Pressing switch