diff options
Diffstat (limited to 'board/trab/tsc2000.c')
| -rw-r--r-- | board/trab/tsc2000.c | 49 |
1 files changed, 46 insertions, 3 deletions
diff --git a/board/trab/tsc2000.c b/board/trab/tsc2000.c index df2d87f..ca68682 100644 --- a/board/trab/tsc2000.c +++ b/board/trab/tsc2000.c @@ -31,6 +31,16 @@ #include "Pt1000_temp_data.h" +/* helper function */ +#define abs(value) (((value) < 0) ? ((value)*-1) : (value)) + +/* + * Maximal allowed deviation between two immediate meassurments of an analog + * thermo channel. 1 DIGIT = 0.0276 °C. This is used to filter sporadic + * "jumps" in measurment. + */ +#define MAX_DEVIATION 18 /* unit: DIGITs of adc; 18 DIGIT = 0.5 °C */ + void spi_init(void) { S3C24X0_GPIO * const gpio = S3C24X0_GetBase_GPIO(); @@ -227,15 +237,48 @@ s32 tsc2000_contact_temp (void) long adc_pt1000, offset; long u_pt1000; long contact_temp; - + long temp1, temp2; tsc2000_reg_init (); tsc2000_set_range (3); - adc_pt1000 = tsc2000_read_channel (14); + /* + * Because of sporadic "jumps" in the measured adc values every + * channel is read two times. If there is a significant difference + * between the two measurements, then print an error and do a third + * measurement, because it is very unlikely that a successive third + * measurement goes also wrong. + */ + temp1 = tsc2000_read_channel (14); + temp2 = tsc2000_read_channel (14); + if (abs(temp2 - temp1) < MAX_DEVIATION) + adc_pt1000 = temp2; + else { + printf ("%s: read adc value (channel 14) exceeded max allowed " + "deviation: %d * 0.0276 °C\n", + __FUNCTION__, MAX_DEVIATION); + printf ("adc value 1: %ld DIGITs\nadc value 2: %ld DIGITs\n", + temp1, temp2); + adc_pt1000 = tsc2000_read_channel (14); + printf ("use (third read) adc value: adc_pt1000 = " + "%ld DIGITs\n", adc_pt1000); + } debug ("read channel 14 (pt1000 adc value): %ld\n", adc_pt1000); - offset = tsc2000_read_channel (15); + temp1 = tsc2000_read_channel (15); + temp2 = tsc2000_read_channel (15); + if (abs(temp2 - temp1) < MAX_DEVIATION) + offset = temp2; + else { + printf ("%s: read adc value (channel 15) exceeded max allowed " + "deviation: %d * 0.0276 °C\n", + __FUNCTION__, MAX_DEVIATION); + printf ("adc value 1: %ld DIGITs\nadc value 2: %ld DIGITs\n", + temp1, temp2); + offset = tsc2000_read_channel (15); + printf ("use (third read) adc value: offset = %ld DIGITs\n", + offset); + } debug ("read channel 15 (offset): %ld\n", offset); /* |