Chapter 9: Breakout Board
1-Wire EEPROM Details
140
Psion Teklogix Omnii HDK User Manual
9.9.2
1-Wire EEPROM Details
The breakout board provides a 1-Wire EEPROM similar to those required in expansion devices to
identify the make and model of the device to Omnii, so that the appropriate device drivers can be
loaded and the device can appear in the Windows Control Panel System applet. By programming
this EEPROM the breakout board can identify itself as any device for development and
testing purposes.
The EEPROM chip (U5) has 1024 bits of memory organized into four memory pages of 256 bits
each. Data is written to an 8-byte scratch pad, verified and copied to the EEPROM memory.
Figure 9.21 1-Wire EEPROM Header J39 Pin Order
For details on programming the EEPROM, see Chapter 8: “EEPROM Specifications”.
A simple interface for programming the breakout board EEPROM from the Omnii hand-held
computer is provided in the HDK Demo application included with the Omnii HDK. See
Chapter 10: “HDK Demo Application” for information on how to install and use this application,
and Section 10.6.2.4: “EEPROM” for specific details regarding EEPROM reading and writing.
Warning: When constructing a cable with external power, ensure all 6 pins are used, with
pins 1 and 2 disconnected. If power is supplied from the cable at the same time
as EXP_3V3 power is being supplied across pins 1 and 2, damage to the board
may result.
Table 9.14 1-Wire EEPROM Header J39 Pinout
Pin
Name
Description
1
EXP_3V3
3.3 V power from EXP_3V3
2
SUP_EEPROM
EEPROM power supply from Omnii (jumper pin 1 & 2)
3
SUP_EXT
EEPROM power supply from external device
(
NO
jumper on pin 1 & 2)
4
1DATA_EEPROM Data
5
GND_EEPROM
Ground
6
NC
No connection
1 2 3 4 5 6
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