ntc_thermistor.rst 2.7 KB

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  1. Kernel driver ntc_thermistor
  2. ============================
  3. Supported thermistors from Murata:
  4. * Murata NTC Thermistors NCP15WB473, NCP18WB473, NCP21WB473, NCP03WB473,
  5. NCP15WL333, NCP03WF104, NCP15XH103
  6. Prefixes: 'ncp15wb473', 'ncp18wb473', 'ncp21wb473', 'ncp03wb473',
  7. 'ncp15wl333', 'ncp03wf104', 'ncp15xh103'
  8. Datasheet: Publicly available at Murata
  9. Supported thermistors from EPCOS:
  10. * EPCOS NTC Thermistors B57330V2103
  11. Prefixes: b57330v2103
  12. Datasheet: Publicly available at EPCOS
  13. Other NTC thermistors can be supported simply by adding compensation
  14. tables; e.g., NCP15WL333 support is added by the table ncpXXwl333.
  15. Authors:
  16. MyungJoo Ham <myungjoo.ham@samsung.com>
  17. Description
  18. -----------
  19. The NTC (Negative Temperature Coefficient) thermistor is a simple thermistor
  20. that requires users to provide the resistance and lookup the corresponding
  21. compensation table to get the temperature input.
  22. The NTC driver provides lookup tables with a linear approximation function
  23. and four circuit models with an option not to use any of the four models.
  24. Using the following convention::
  25. $ resistor
  26. [TH] the thermistor
  27. The four circuit models provided are:
  28. 1. connect = NTC_CONNECTED_POSITIVE, pullup_ohm > 0::
  29. [pullup_uV]
  30. | |
  31. [TH] $ (pullup_ohm)
  32. | |
  33. +----+-----------------------[read_uV]
  34. |
  35. $ (pulldown_ohm)
  36. |
  37. -+- (ground)
  38. 2. connect = NTC_CONNECTED_POSITIVE, pullup_ohm = 0 (not-connected)::
  39. [pullup_uV]
  40. |
  41. [TH]
  42. |
  43. +----------------------------[read_uV]
  44. |
  45. $ (pulldown_ohm)
  46. |
  47. -+- (ground)
  48. 3. connect = NTC_CONNECTED_GROUND, pulldown_ohm > 0::
  49. [pullup_uV]
  50. |
  51. $ (pullup_ohm)
  52. |
  53. +----+-----------------------[read_uV]
  54. | |
  55. [TH] $ (pulldown_ohm)
  56. | |
  57. -+----+- (ground)
  58. 4. connect = NTC_CONNECTED_GROUND, pulldown_ohm = 0 (not-connected)::
  59. [pullup_uV]
  60. |
  61. $ (pullup_ohm)
  62. |
  63. +----------------------------[read_uV]
  64. |
  65. [TH]
  66. |
  67. -+- (ground)
  68. When one of the four circuit models is used, read_uV, pullup_uV, pullup_ohm,
  69. pulldown_ohm, and connect should be provided. When none of the four models
  70. are suitable or the user can get the resistance directly, the user should
  71. provide read_ohm and _not_ provide the others.
  72. Sysfs Interface
  73. ---------------
  74. =============== == =============================================================
  75. name the mandatory global attribute, the thermistor name.
  76. =============== == =============================================================
  77. temp1_type RO always 4 (thermistor)
  78. temp1_input RO measure the temperature and provide the measured value.
  79. (reading this file initiates the reading procedure.)
  80. =============== == =============================================================
  81. Note that each NTC thermistor has only _one_ thermistor; thus, only temp1 exists.