Datasheet
Evaluates: SPI and SMBus/I
2
C-Compatible Parts
CMAXQUSB User’s Guide
7
Connector P7: SMBus/I
2
C Test Points
For convenience, the SMBus/I
2
C interface signals are
connected to labeled pins on header P7. See Table 5.
Connector P8: SPI Test Points
For convenience, the SPI interface signals are connect-
ed to labeled pins on header P8. See Table 6.
Detailed Description of Firmware
The CMAXQUSB firmware was developed using
the MAX-IDE assembly language development
environment. Full source code is available at
www.maxim-ic.com/tools/evkit under the project
name
CMAXQUSB Firmware
.
If designing a custom EV kit board requiring an inter-
rupt service routine in custom firmware, GPIO signals
K5–K8 are the suggested locations for the interrupt sig-
nal. The standard CMAXQUSB firmware does not ser-
vice interrupts on any GPIO pins.
Troubleshooting
Problem: Software reports it cannot find the board.
• Verify that the CMAXQUSB power LED is lit.
• Verify that the USB cable is connected.
• Verify that Windows plug-and-play detected the
board. Bring up Control Panel -> System -> Device
Manager, and look at what device nodes are indicat-
ed for the USB. If there is an “unknown device” node
attached to the USB, delete it—this forces plug-and-
play to try again.
Problem: Unable to find SMBus/I
2
C device.
• Verify that the SCL and SDA signals are pulled up to
VDD. CMAXQUSB DIP switch SW1 enables the on-
board resistors. There must be pullup resistors
somewhere on the bus.
• If using wires to connect the CMAXQUSB to your
target board, make certain that you have not
swapped the SCL and SDA signals. Verify that the
ground return is connected.
P7 PIN LABEL FUNCTION
1 VDD VDD Power Supply
2 SDA SMBus/I
2
C SDA (Data)
3 GND Ground Return
4 SCL SMBus/I
2
C SCL (Clock)
Table 5. Connector P7 Description
P8 PIN LABEL FUNCTION
1 VDD VDD Power Supply
2 MISO Master-In, Slave-Out Data
3 MOSI Master-Out, Slave-In Data
4 SCLK SPI Clock
5CS
Chip Select. Configurable active
high or active low.
6 GND Ground Return
Table 6. Connector P8 Description