Hello list,

inside the automatic U-Boot patch tracking system a new ticket [DNX#2006040142000759] was created:

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In message 42AFEBD3.3050008@imc-berlin.de you wrote:

...

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").

Ummm...

...

This trivial fix is needed:

Wait a moment...

...

--- 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);

This is not the right way to fix it. I reject this patch.

dtt_read() is declared to return "int", so no such cast should be needed, i. e. you fix the symptoms instead of the cause.

I think the patch must be done in dtt_read(); IMO the line

return ((int)((short)data[1] + (((short)data[0]) << 8)));

is wrong; it should read

return ((short)((short)data[1] + (((short)data[0]) << 8)));

or, even better,

short rc_s; ... rc_s = (short)data[1] + (((short)data[0]) << 8); return (rc_s);

And the same problem is with dlen == 1 - it should read

return ((signed char)data[0]);

Do you agree with this assessment? And can you please confirm that my suggested patch fixes your problem, too?

Best regards,

Wolfgang Denk

-- Software Engineering: Embedded and Realtime Systems, Embedded Linux Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de Of all possible committee reactions to any given agenda item, the reaction that will occur is the one which will liberate the greatest amount of hot air. -- Thomas L. Martin

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Your U-Boot support team