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EEPROM
Considerations
Revision 1.6 – 13th May 2008 |
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Some
pointer device controllers have onboard EEPROM (Electrically
Erasable Programmable Read Only Memory). EEPROM can be used to store
information pertinent to the controller and also offers a memory storage area
for applications and drivers to store data.
One of the main uses for this memory with UPDD is to store the
calibration data within the controller rather than locally on a system. In all cases an absolute pointer device needs to be calibrated with
the systems video display such that the point of contact is aligned with the
video image. UPDD
calibration is performed by drawing points on the video display at known
locations that are then touched and the touch co-ordinates are noted for the
given point of display. The driver can then use this data to scale and map
the touch input to the video location.
This information, known as the calibration data, needs to be stored
for future reference, such that the device is calibrated at each system power
up. This information can be stored locally on the system (e.g. the system’s
persistent memory, within a file, etc) or externally in the controller’s
EEPROM. Given that UPDD supports 100’s of different pointer devices, all with
different characteristics, our driver generally stores its calibration data
locally within the system. However, there are cases where it is desirable to store calibration
data externally. This is especially true of systems where the calibration
data cannot be stored locally, such as some embedded system configurations
where the entire system is locked down and any changes made are lost when the
device is powered off. In other cases
it is desirable to calibrate a touch screen prior to usage on a similar
system so that it is calibrated when first used and will only require
recalibrating if the EEPROM calibration is inaccurate. As and when we have been requested to support EEPROM calibration for a
given controller it has been added.
When one of these controllers is defined in the UPDD build (and with EEprom enabled)
and added in the UPDD Console as an active device an EEPROM check box is
shown on the UPDD Console, Calibration screen.
When this EEPROM check box is enabled (or set internally in the UPDD
settings), EEPROM calibration storage is employed at the NEXT calibration. It
is important to note that this setting enables the EEPROM calibration
procedure such that at the point of calibration the EEPROM calibration
procedure is invoked. Depending on the
controller in use there may be a further stage needed to retrieve this data
at appropriate times, such as a system power up. EEPROM calibration falls into two distinct categories, one whereby UPDD stores its own calibration data in EEPROM and one whereby the controller’s own firmware calibration procedure is invoked, more commonly known as a firmware calibration. Where UPDD stores it own data then there is a requirement to retrieve the data at system start up / driver load. Where firmware calibration is use the controller internally rescales the co-ordinate output to be calibrated with the video system and thus generated co-ordinate data is “pre-calibrated” and therefore a retrieval process is not relevant. The implementation of each supported controller is discussed below. Supported EEPROM controllersThe following controllers are currently supported; Firmware calibrationUPDD invokes the controller’s firmware commands to perform calibration such that scaled touch co-ordinates are sent. In most cases, the calibration function implemented within the
controller’s firmware dictates the number and location of the calibration
points and this will be reflected within the available settings on the
calibration dialog. Following calibration the controller’s output is adjusted to map to the video display. DMC FIT 10 When enabled the calibration procedure is restricted to the range of
calibration points supported by the controller’s firmware calibration
procedure. 3M Touch Systems,
SC400,500,800 UPDD invokes the controller’s 3 point calibration procedure. In some
older versions of the driver it is important to manually set the number of
calibration points to 3 at the same time as enabling EEPROM. This procedure is also required to initialise
/ linearise the controller and should be performed
at least once irrespective of the need to subsequently utilise
EEPROM functionality. ELO TouchSystems, SmartSet UPDD invokes the controller’s 3 point calibration procedure. Internally
it actually uses a 2 point algorithm with the 3rd point to
determine orientation. EEPROM storage of UPDD
calibration data
UPDD calibration procedure stores its own calibration data in the controller’s EEPROM. To utilize (retrieve) the calibration data stored in the controller the calibration program must be invoked, typically at startup, using the command ‘tbcalib eeprom’, as detailed in the Calibration program document. If this is not performed then locally stored calibration data is used. TBcalib returns an error code if the calibration data checksum is incorrect (e.g. retrieving calibration data from a controller that has no calibration data such as a new controller used for the first time). In locked down environments, such as embedded systems, it is important to retrieve the calibration data from the controller as any data stored locally is likely to be loss over a reboot, reverting back to the data built into the embedded image. Zytronic, x-y Hampshire
Touch EEprom capable controllers Due to current firmware limitations the data is written to the controller, 1 byte at a time, and depending on the number of calibration points can take a significant time to store and retrieve. 4 points takes approx 20 seconds. Enabling EEprom protocolsGive that the EEprom interface to each controller
is unique there is separate protocol code written for each controller. When
we define a controller we identify the protocol to use. If the EEprom
protocol setting is blank then the EEprom option
will not be shown. If you are using a
driver which supports one of the above controllers but does not show the EEprom option then it is likely the EEprom
setting was/is not defined in the definition of the driver at build
time. If this is the case contact
Touch-Base to request an updated build. The protocol setting protocol identifers are
as follows:
For UPDD
4.1.x the EEProm protocol id setting is held in the
UPDD settings file, TBUPDD.INI, within the branch [updd\paramaters\n]
and called ‘eeprom protocol’. Other EEprom
settings within the file are redundant in 4.1.x and above. Adding EEPROM support
We can
add support in UPDD for any EEPROM enabled controller as required once
supplied the technical documentation which describes the controller’s EEPROM
calibration interface. If you
are a controller manufacturer and would like to add EEPROM capabilities to
you controller, we are aware of three methods that have been utilised as
described below: Raw Mode
Firmware
commands are used to specify that raw blocks of data can be stored and
retrieved from EEPROM. In this mode,
UPDD simply stores and retrieves the calibration from the controllers EEPROM. This is
the simplest method to implement for both the firmware developers and our
driver as the EEPROM read and write functions are already built into the UPDD
calibration program. Formatted mode
The
controller’s firmware dictates the format of the calibration data passed to
the controller which is further processed by the controller. The co-ordinate data is then scaled and
mapped to a grid co-ordinate range, based on the formatted data. In this case the calibration program has to
gather calibration data as dictated by the data format requirement. Co-operative mode
The
controller’s firmware exposes calibration commands such that the calibration program
issues a firmware command for each calibration point displayed and the
firmware captures the calibration points in real-time. The number of calibration points and the
pattern used is dictated by the firmware’s requirements. The co-ordinate data is then scaled and
mapped to a grid co-ordinate range, based on the capture calibration
information. ContactFor further information or technical assistance please email the technical support team at technical@touch-base.com |
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