diff options
author | Vic Yang <victoryang@chromium.org> | 2012-02-15 15:36:40 -0800 |
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committer | Vic Yang <victoryang@chromium.org> | 2012-02-15 16:34:54 -0800 |
commit | 93d77ada6ca328044496d4d42364bc6f70b468d5 (patch) | |
tree | 2684b23d20b0434183cf36d679a3750fb4282e4f /common/temp_sensor.c | |
parent | 8236345574850df798197878d413e87f3cdc09b6 (diff) | |
download | chrome-ec-93d77ada6ca328044496d4d42364bc6f70b468d5.tar.gz |
Change TMP006 temperature calculation to use FP.
The temperature calculation currently uses fixed point operations.
Change it to use floating point for better readability and maintenance.
Also changes disable_fpu() to accept parameter which serves as
optimization barrier to prevent floating point operations after
disabling FPU.
BUG=chrome-os-partner:7801
TEST=In console, tempremote "tempremote 29715 -105000 6390" gives 28506.
Change-Id: Ib766904b8feb9a78eac9f7cd53afeca85091c5a5
Signed-off-by: Vic Yang <victoryang@chromium.org>
Diffstat (limited to 'common/temp_sensor.c')
-rw-r--r-- | common/temp_sensor.c | 70 |
1 files changed, 30 insertions, 40 deletions
diff --git a/common/temp_sensor.c b/common/temp_sensor.c index bc794874ab..80b3166e32 100644 --- a/common/temp_sensor.c +++ b/common/temp_sensor.c @@ -11,6 +11,9 @@ #include "util.h" #include "console.h" #include "board.h" +#include "task.h" +#include "fpu.h" +#include "math.h" /* Defined in board_temp_sensor.c. Must be in the same order as * in enum temp_sensor_id. @@ -44,52 +47,39 @@ int temp_sensor_tmp006_read_die_temp(const struct temp_sensor_t* sensor) * Parameters: * Tdie: Die temperature in 1/100 K. * Vobj: Voltage read from register 0. In nV. - * S0: Sensitivity factor in 1/1000. + * S0: Sensitivity factor in 1e-17. * Return: * Object temperature in 1/100 K. */ -int temp_sensor_tmp006_calculate_object_temp(int Tdie, int Vobj, int S0) +int temp_sensor_tmp006_calculate_object_temp(int Tdie_i, int Vobj_i, int S0_i) { - int32_t Tx, S19, Vos, Vx, fv9, ub, lb; - - /* Calculate according to TMP006 users guide. - * Division is delayed when possible to preserve precision, but should - * not cause overflow. - * Assuming Tdie is between 200K and 400K, and S0 between 3e-14 and - * 9e-14, the maximum value during the calculation should be less than - * (1 << 30), which fits in int32_t. - */ - Tx = Tdie - 29815; - /* S19 is the sensitivity multipled by 1e19 */ - S19 = S0 * (100000 + 175 * Tx / 100 - - 1678 * Tx / 100 * Tx / 100000) / 1000; - /* Vos is the offset voltage in nV */ - Vos = -29400 - 570 * Tx / 100 + 463 * Tx / 100 * Tx / 10000; + float Tdie, Vobj, S0; + float Tx, S, Vos, Vx, fv, Tobj, T4; + int Tobj_i; + + enable_fpu(); + + Tdie = (float)Tdie_i * 1e-2f; + Vobj = (float)Vobj_i * 1e-9f; + S0 = (float)S0_i * 1e-17f; + + /* Calculate according to TMP006 users guide. */ + Tx = Tdie - 298.15f; + /* S is the sensitivity */ + S = S0 * (1.0f + 1.75e-3f * Tx - 1.678e-5f * Tx * Tx); + /* Vos is the offset voltage */ + Vos = -2.94e-5f - 5.7e-7f * Tx + 4.63e-9f * Tx * Tx; Vx = Vobj - Vos; - /* fv9 is Seebeck coefficient f(Vobj) multipled by 1e9 */ - fv9 = Vx + 134 * Vx / 100000 * Vx / 100000; - - /* The last step in the calculation involves square root, so we use - * binary search. - * Assuming the object temperature is between 200K and 400K, the search - * should take at most 14 iterations. - */ - ub = 40000; - lb = 20000; - while (lb != ub) { - int32_t t, rhs, lhs; - - t = (ub + lb) / 2; - lhs = t / 100 * t / 10000 * t / 10000 * (S19/100) / 1000 * t; - rhs = Tdie / 100 * Tdie / 10000 * Tdie / 10000 * (S19/100) / 1000 * - Tdie + fv9 * 1000; - if (lhs > rhs) - ub = t; - else - lb = t + 1; - } + /* fv is Seebeck coefficient f(Vobj) */ + fv = Vx + 13.4f * Vx * Vx; + + T4 = Tdie * Tdie * Tdie * Tdie + fv / S; + Tobj = sqrtf(sqrtf(T4)); + Tobj_i = (int32_t)(Tobj * 100.0f); + + disable_fpu(Tobj_i); - return ub; + return Tobj_i; } int temp_sensor_tmp006_read_object_temp(const struct temp_sensor_t* sensor) |