ntc_thermistor 2.6 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
  6. Prefixes: 'ncp15wb473', 'ncp18wb473', 'ncp21wb473', 'ncp03wb473',
  7. 'ncp15wl333', 'ncp03wf104'
  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. The four circuit models provided are:
  25. $: resister, [TH]: the thermistor
  26. 1. connect = NTC_CONNECTED_POSITIVE, pullup_ohm > 0
  27. [pullup_uV]
  28. | |
  29. [TH] $ (pullup_ohm)
  30. | |
  31. +----+-----------------------[read_uV]
  32. |
  33. $ (pulldown_ohm)
  34. |
  35. --- (ground)
  36. 2. connect = NTC_CONNECTED_POSITIVE, pullup_ohm = 0 (not-connected)
  37. [pullup_uV]
  38. |
  39. [TH]
  40. |
  41. +----------------------------[read_uV]
  42. |
  43. $ (pulldown_ohm)
  44. |
  45. --- (ground)
  46. 3. connect = NTC_CONNECTED_GROUND, pulldown_ohm > 0
  47. [pullup_uV]
  48. |
  49. $ (pullup_ohm)
  50. |
  51. +----+-----------------------[read_uV]
  52. | |
  53. [TH] $ (pulldown_ohm)
  54. | |
  55. -------- (ground)
  56. 4. connect = NTC_CONNECTED_GROUND, pulldown_ohm = 0 (not-connected)
  57. [pullup_uV]
  58. |
  59. $ (pullup_ohm)
  60. |
  61. +----------------------------[read_uV]
  62. |
  63. [TH]
  64. |
  65. --- (ground)
  66. When one of the four circuit models is used, read_uV, pullup_uV, pullup_ohm,
  67. pulldown_ohm, and connect should be provided. When none of the four models
  68. are suitable or the user can get the resistance directly, the user should
  69. provide read_ohm and _not_ provide the others.
  70. Sysfs Interface
  71. ---------------
  72. name the mandatory global attribute, the thermistor name.
  73. temp1_type always 4 (thermistor)
  74. RO
  75. temp1_input measure the temperature and provide the measured value.
  76. (reading this file initiates the reading procedure.)
  77. RO
  78. Note that each NTC thermistor has only _one_ thermistor; thus, only temp1 exists.