diagnostic modes for products with atmel ? capacitive-touch ics 1. introduction there are many types of atmel capacitive-touch integrated circuits (qt ? ics) with interfaces as diverse as simple pin-per-key (ppk) to serial links for data communication. to support product development throughout production testing, it is often useful to obtain data from the qt ic by using the diagnostic modes in a product?s main microcontroller (mcu). this application note discusses the vari ous points to be considered when designing diagnostic modes for your product. the topics in this application note include: ? diagnostic mode entry ? diagnostic data output ? displayed information ? pass-through from qt ic to pc ? production testing 2. why do i need diagnostics? making diagnostic information readily avai lable encourages monitoring and promotes understanding of the product under development. it also permits the detection of unusual conditions or, in the event of a fault, the retrieval of useful information while the fault condition prevails. 3. diagnostic mode entry there are three basic methods of initiating diagnostic mode during product testing: ? key sequence ? external command ? option setting 3.1 entry by key sequence key sequences are particularly useful because external equipment or product modifications are not required. however, the method is not always successful if the touch is not calibrated or if an error condition occurs. a typical key sequence could be: 1. press key a for 3 seconds, then release. 2. press key b for 3 seconds, then release. 3. press key c for 3 seconds, then release. 10704a?at42?10/08 diagnostic modes for qt ics application note QTAN0016
2 10704a?at42?10/08 diagnostic modes for qt ics this is preferable to a mu lti-key instruction such as: 1. press key a , key b and key c simultaneously for three seconds, then release. multi-key instructions rest rict the use of atmel?s adjacent key suppression ? (aks ? ) feature, available in many qt ics, and may therefore re quire that key centers are more widely spaced. 3.2 entry by external command diagnostic mode can be initiated by external co mmands issued via rs-232, usb, or a similar communications protocol. the interface can also be used to log data. however, the disadvantages of this method are that: ? external equipment is required ? which is not always convenient. ? test results may be affected ? for example by creating alternate paths to ground. 3.3 entry by option setting to initiate diagnostic mode, options such as jumpers, dip switches, non-volatile memory settings, etc. can be read at start-up and/or during operation. this method is particularly useful for tests that cycle the product's power, but is not always convenient or easy to implement. 3.4 mode entry considerations usually, it is advantageous to su pport all three methods of initiating diagnostic modes. if several diagnostic modes are used, consider using a single entry method to step through the modes (including normal display). the benefits are that: ? operators need only remember a single key sequence or serial command. ? code size is minimized. ? additional diagnostic modes can be added without changing the base code or the product documentation. if the product has an off , cancel or clear key, it can be used to cancel all diagnostics: for example, by pressing the key for two or three seconds, or consecutively. this arrangement offers users an intuitive exit from diagnostic mode. diagnostic software builds (i.e. using #ifdef diag) are also an option, but they are inconvenient because the code is not available in the producti on compile. often, optional code is not updated with software changes, so it may not be usable when needed. moreover, special compiles may be necessary when produ ct memory is limited. 4. diagnostic data output diagnostic information can be read by using the product's own display and/or an external interface. the product display (for example, an led or lcd) is particularly convenient because additional external equipment is not required. an external interface such as rs-232 or usb allows data to be logged and commands to be entered. the disadvantage is that external equipment is necessary, which may affect test results (for example, by presenting alternate paths to ground). external jigs with simple led displays on ppk or bi nary interfaces are us eful for products that are not equipped with an mcu.
3 10704a?at42?10/08 diagnostic modes for qt ics 5. displayed information if the product does not have sufficient display elements to simultaneously present a set of information, consider the use of a single diagnostic mode that displays the data in a timed sequence (see figure 5-1 ). figure 5-1. example of displayed diagnostic information ?qtl?, last touched key id, reference level, signal level, delta, repeat. if [n] keys are detected at same time: ?qtn?, first key id, second key id ... last key id, repeat. ?qts?, key status byte 0, key status byte 1 ... repeat. ?qte?, qt error byte 0 ... ?qtf?, qt fmea byte 0 ... repeat. note that using an identifier in diagnostic m odes is useful in understanding what is being displayed (for example, the identifiers ?qtl?, ?qts? and ?qte? in figure 5-1 ). for products with ppk interfaces, it is useful to have a diagnostic mode that displays an idle pattern when no keys are pressed, and which cycles the identities of all pressed keys. 6. pass-through from qt ic to pc there are demonstration kits and matching pc software for many qt ics. a diagnostic mode that passes data directly from the qt ic to the pc (as in the demonstration kits), allows the pc software to be used to diagnose and tune the product. in some circumstances it is necessary to configure the product's mcu to buffer data and thus accommodate different data rates and flow control signals such as drdy. 7. production testing by keeping production testing in mind duri ng design, diagnostic modes can be embedded in production jigs. key-activated modes can be used by manual test operators to perform and view test results. modes selected via external interfaces allow automated test equipment to select tests, retrieve results for pass/fail logs, and monitor variations in product criteria over the production life of the product.
10704a?at42?10/08 headquarters international atmel corporation 2325 orchard parkway san jose, ca 95131 usa tel: 1(408) 441-0311 fax: 1(408) 487-2600 atmel asia unit 01-05 & 16, 19/f bea tower, millennium city 5 418 kwun tong road kwun tong kowloon hong kong tel: (852) 2245-6100 fax: (852) 2722-1369 atmel europe le krebs 8, rue jean-pierre timbaud bp 309 78054 saint-quentin-en- yvelines cedex france tel: (33) 1-30-60-70-00 fax: (33) 1-30-60-71-11 atmel japan 9f, tonetsu shinkawa bldg. 1-24-8 shinkawa chuo-ku, tokyo 104-0033 japan tel: (81) 3-3523-3551 fax: (81) 3-3523-7581 touch technology division 1 mitchell point ensign way hamble southampton hampshire so31 4rf united kingdom tel: (44) 23-8056-5600 fax: (44) 23-8045-3939 product contact web site www.atmel.com technical support qprox.support@atmel.com sales contact qprox.sales@atmel.com literature requests www.atmel.com/literature disclaimer: the information in this document is provid ed in connection with atmel products. no li cense, express or implied, by estoppel or otherwise, to any intellec- tual property right is granted by this document or in connection with the sale of atmel products. except as set forth in atmel?s terms and conditions of sale located on atmel?s web site, atmel assumes no liab ility whatsoever and disclaims any express, implied or statutory warranty relating to its products including, but not limited to , the implied warranty of merchantability, fitness for a partic- ular purpose, or non-infringement. in no event shall atmel be liable for any direct, indirect, consequential, punitive, special or incidental damages (includin g, without limitation, damages for loss and profit s, business interrupt ion, or loss of informa- tion) arising out of the use or inability to use this document, even if atmel has been advised of the possibility of such dam- ages. atmel makes no representations or warranties with respect to the accuracy or completeness of the contents of this document and reserves the right to make changes to specifications and produ ct descriptions at any time without notice. atme l does not make any commitment to update the information contained herein. unless specifically provided otherwise, atmel products are no t approved for use in automotive applications, medical application s (including, but not limited to, life sup- port systems and other medical equipment), avionics, nuclear a pplications, or other high risk applications (e.g., applications that, if they fail, can be reasonably expected to result in significant personal injury or death). ? 2008 atmel corporation. all rights reserved. atmel ? , atmel logo and combinations thereof, and others are registered trademarks, qt ? , aks ? , adjacent key suppression ? and others are trademarks of atmel corporation or its subsidiaries. other terms and product names may be regis- tered trademarks or trademarks of others.
|
