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Gigabeat S: Simplify and use a thermistor lookup table (ADC value => deg C) . Saves some binsize.

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@19583 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Michael Sevakis 2008-12-24 23:36:33 +00:00
parent 377b42b63b
commit 4f2bc16f5c
1 changed files with 44 additions and 42 deletions
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86
firmware/target/arm/imx31/gigabeat-s/powermgmt-imx31.c
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@ -53,36 +53,6 @@ const unsigned short percent_to_volt_charge[11] =
3480, 3550, 3590, 3610, 3630, 3650, 3700, 3760, 3800, 3910, 3990
};
/**
* Fixed-point natural log
* taken from http://www.quinapalus.com/efunc.html
* "The code assumes integers are at least 32 bits long. The (positive)
* argument and the result of the function are both expressed as fixed-point
* values with 16 fractional bits, although intermediates are kept with 28
* bits of precision to avoid loss of accuracy during shifts."
*/
static long flog(int x)
{
long t,y;
y=0xa65af;
if(x<0x00008000) x<<=16, y-=0xb1721;
if(x<0x00800000) x<<= 8, y-=0x58b91;
if(x<0x08000000) x<<= 4, y-=0x2c5c8;
if(x<0x20000000) x<<= 2, y-=0x162e4;
if(x<0x40000000) x<<= 1, y-=0x0b172;
t=x+(x>>1); if((t&0x80000000)==0) x=t,y-=0x067cd;
t=x+(x>>2); if((t&0x80000000)==0) x=t,y-=0x03920;
t=x+(x>>3); if((t&0x80000000)==0) x=t,y-=0x01e27;
t=x+(x>>4); if((t&0x80000000)==0) x=t,y-=0x00f85;
t=x+(x>>5); if((t&0x80000000)==0) x=t,y-=0x007e1;
t=x+(x>>6); if((t&0x80000000)==0) x=t,y-=0x003f8;
t=x+(x>>7); if((t&0x80000000)==0) x=t,y-=0x001fe;
x=0x80000000-x;
y-=x>>15;
return y;
}
/* Returns battery voltage from ADC [millivolts] */
unsigned int battery_adc_voltage(void)
{
@ -134,30 +104,62 @@ unsigned int cccv_regulator_dissipation(void)
/* Returns battery temperature from ADC [deg-C] */
int battery_adc_temp(void)
{
unsigned int value = adc_read(ADC_BATTERY_TEMP);
/* E[volts] = value * 2.3V / 1023
* R[ohms] = E/I = E[volts] / 0.00002[A] (Thermistor bias current source)
*
* Steinhart-Hart thermistor equation (sans "C*ln^2(R)" term because it
* has negligible effect):
* Steinhart-Hart thermistor equation:
* [A + B*ln(R) + D*ln^3(R)] = 1 / T[°K]
*
* Coeffients that fit experimental data (one thermistor so far, one run):
* A = 0.0013002631685462800
* B = 0.0002000841932612330
* D = 0.0000000640446750919
*
* Fixed-point output matches the floating-point version for each ADC
* value.
*/
static const unsigned short ntc_table[] =
{
#if 0 /* These have degree deltas > 1 (except the final two) so leave them
* out. 70 deg C upper limit is quite sufficient. */
0, /* INF */ 1, /* 171 */ 2, /* 145 */ 3, /* 130 */
4, /* 121 */ 5, /* 114 */ 6, /* 108 */ 7, /* 104 */
8, /* 100 */ 9, /* 96 */ 10, /* 93 */ 11, /* 91 */
12, /* 88 */ 13, /* 86 */ 14, /* 84 */ 15, /* 82 */
16, /* 81 */ 17, /* 79 */ 18, /* 78 */ 19, /* 76 */
20, /* 75 */ 21, /* 74 */ 22, /* 72 */ 23, /* 71 */
#endif
24, /* 70 */ 25, /* 69 */ 26, /* 68 */ 27, /* 67 */
28, /* 66 */ 30, /* 65 */ 31, /* 64 */ 32, /* 63 */
33, /* 62 */ 35, /* 61 */ 36, /* 60 */ 38, /* 59 */
39, /* 58 */ 41, /* 57 */ 43, /* 56 */ 45, /* 55 */
47, /* 54 */ 49, /* 53 */ 51, /* 52 */ 53, /* 51 */
56, /* 50 */ 58, /* 49 */ 61, /* 48 */ 63, /* 47 */
66, /* 46 */ 69, /* 45 */ 73, /* 44 */ 76, /* 43 */
80, /* 42 */ 83, /* 41 */ 87, /* 40 */ 92, /* 39 */
96, /* 38 */ 101, /* 37 */ 106, /* 36 */ 111, /* 35 */
116, /* 34 */ 122, /* 33 */ 128, /* 32 */ 135, /* 31 */
142, /* 30 */ 149, /* 29 */ 156, /* 28 */ 164, /* 27 */
173, /* 26 */ 182, /* 25 */ 192, /* 24 */ 202, /* 23 */
212, /* 22 */ 224, /* 21 */ 236, /* 20 */ 249, /* 19 */
262, /* 18 */ 277, /* 17 */ 292, /* 16 */ 308, /* 15 */
325, /* 14 */ 344, /* 13 */ 363, /* 12 */ 384, /* 11 */
406, /* 10 */ 429, /* 9 */ 454, /* 8 */ 480, /* 7 */
509, /* 6 */ 539, /* 5 */ 571, /* 4 */ 605, /* 3 */
641, /* 2 */ 680, /* 1 */ 722, /* 0 */ 766, /* -1 */
813, /* -2 */ 864, /* -3 */ 918, /* -4 */ 976, /* -5 */
};
unsigned int value = adc_read(ADC_BATTERY_TEMP);
if (value > 0)
{
int R = 2070000 * value;
long long ln = flog(R) + 83196;
long long t0 = 425890304133ll;
long long t1 = 1000000*ln;
long long t3 = ln*ln*ln / 13418057;
return ((32754211579494400ll / (t0 + t1 + t3)) - 27315) / 100;
unsigned i;
for (i = 1; i < ARRAYLEN(ntc_table); i++)
{
if (ntc_table[i] > value)
break;
}
return 71 - i;
}
return INT_MIN;