Hi there,
there's a terrible bug in the current U-Boot CVS concerning DDT:
For temperature below zero the function dtt_get_temp() (at least for lm75) returns wrong values!
... DTT: 1 is 235 C LCD: Hitachi TX14D11 5,7" 320x240 TFT (235°C) WDT: disabled
This is because of the use of an "int" although the lm75 only returns two byte ("signed short").
This trivial fix is needed:
Index: u-boot/dtt/lm75.c =================================================================== RCS file: /cvsroot/u-boot/u-boot/dtt/lm75.c,v retrieving revision 1.2 diff -u -r1.2 lm75.c --- u-boot/dtt/lm75.c 27 Jun 2003 21:32:38 -0000 1.2 +++ u-boot/dtt/lm75.c 15 Jun 2005 08:44:21 -0000 @@ -174,7 +170,7 @@
int dtt_get_temp(int sensor) { - return (dtt_read(sensor, DTT_READ_TEMP) / 256); + return ( ((signed short) dtt_read(sensor, DTT_READ_TEMP)) / 256); } /* dtt_get_temp() */
#endif /* CONFIG_DTT_LM75 */
Then the output is correct:
... DTT: 1 is -28 C LCD: Hitachi TX14D11 5,7" 320x240 TFT (-28°C) CCFL: disabled (too cold!) WDT: disabled
I am afraid this is an issues on all DTT in U-Boot. Some even only use "uchar".
Comments?
-- Steven