9 Feb 2010 7:30:38
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 Acqura now have Philips microcontrollers available for sale. If you need P89C668, P89C669, LPC76x or LPC900 family devices, check out our low MOQ's
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Take a look at our new forums. If you have a question about the 8xC51, LPC900, or MX families (or any 8051-related query) then ask your question here.
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| User laffelt has posted this comment in the General Forum |
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| LPC936 A/D or EEPROM problem |
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We have manufactured a product for several years which uses the P89LPC936 chip, currently there are over 1000 units in the field. Channels 2 & 3 on A/D converter 0 are used with an external multiplexor chip to read a four-wire resistive touchscreen. The touchscreen is calibrated here at the factory and the minimum and maximum x & y values are saved in the internal EEPROM. Those values are read on power-up and used to scale the touches into pixel values. The A/D converter is running at ~2.4MHz using the /3 divisor and we use the internal 7.3MHz clock for the main CPU clock, and it is set to continually scan channels 2 & 3.
We have now seen a low but significant qty of units returned from the field with touchscreen problems in two areas;
1- X or Y scaling problems (wrong functions are activated)
2- Difficulty detecting when nothing is touching the touchscreen. (s/b 0V)
The voltages on the A/D inputs look normal when compared to other units, even ones that have been in the field for several years. The A/D inputs have a 10k to ground to ensure that the inputs go to 0 with no touches and they also drain any capacitance between the two parallel plate (small but it is present). To read the touchscreen calibration values from the EEPROM I have to erase the flash sectors as the security bits are set. Once the program area is erased I can read the EEPROM values and they are within a few A/D counts of ideal. But now once I re-write the same program into the flash the product works perfectly!
The A/D converter is initialized as follows:
EADEE = 0; // No interrupts
ADMODA = 0x04; // Auto scan, continuous mode
ADMODB = 0x40; // Clock divisor = 3;
ADINS = 0x0C; // Channels 2 & 3
ADCON0 = 0x05; // Enable and start immediately
The EEPROM does not show data read errors in any other areas of the program that use it, and the EEPROM dummy read from the errata is in the init code even though Vcc rises much faster (~400uS) than the warning in the errata (10mS).
I am wondering if anyone has seen anything *remotely* like this or has any ideas.
Thanks!
Larry Affelt
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| Click here to see the whole discussion thread. |
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PPA900-DIP20 |
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PDS900 programming adapter for P89LPC92x devices in DIP20 Packages |
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The PPA900-DIP20 is an optional package adaptor for use with the PDS900 device programmer for the Philips P89LPC900 family of microcontrollers.
It plugs onto the PDS900 programmer and allows devices in the DIP20 through-hole-mount package to be programmed.
Note: This programming adaptor is specific to the PDS900 - it should not be assumed that it can be used with any other programmer for the Philips P89LPC900 family devices.
Click here for a comprehensive selection guide showing which emulation and programming system and associated emulation and programming adaptors you will require for all of the LPC900 family devices.
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