Revision: 1844
Author: eur.van.andel
Date: Fri Mar 26 14:16:03 2010
Log: library for MCP9800 I2C temperature sensor
http://code.google.com/p/jallib/source/detail?r=1844
Added:
/trunk/include/external/temperature/mcp9800.jal
=======================================
--- /dev/null
+++ /trunk/include/external/temperature/mcp9800.jal Fri Mar 26 14:16:03 2010
@@ -0,0 +1,90 @@
+-- Title: mcp9800
+-- Author: Eur van Andel, [email protected] Copyright (c) 2010
+-- Compiler: =2.4m
+--
+-- This file is part of jallib (http://jallib.googlecode.com)
+-- Released under the ZLIB license
(http://www.opensource.org/licenses/zlib-license.html)
+--
+-- Description: this library works with the MCP9800 temperature sensor
form microchip
+-- The MCP9800 can do 9 to 12 bit temperature measurement resolution
+-- in the 12bit mode, the LSb represents 1/16ºC
+-- only 12 bit routines are given here
+
+-- Uses: i2c_hardware and i2c_level1 I2C libraries
+
+-- Datasheet: DS21909B
+
+
+-- MCP9800 I2C sensor
+-- part used is MCP9800/02A0 with internal adress set to 0b1001_0000, last
bit is read /write
+-- register pointer map:
+-- 0b0000_0000 temperature register (16 bits)
+-- 0b0000_0001 configuration register ( 8 bits)
+-- 0b0000_0010 temperature Hysteresis register (8 bits)
+-- 0b0000_0011 temperature Limit-set register (8 bits)
+
+alias i2c_scl is pin_c3
+alias i2c_scl_direction is pin_c3_direction
+alias i2c_sda is pin_c4
+alias i2c_sda_direction is pin_c4_direction
+
+-- i2c setup
+const word _i2c_bus_speed = 1 ; * 100kHz
+const bit _i2c_level = true ; i2c levels (not SMB)
+
+include i2c_hardware
+
+i2c_initialize()
+
+var byte i2c_tx_buffer[10]
+var byte i2c_rx_buffer[10]
+
+include i2c_level1 -- send_receive functions
+
+
+
+const byte mcp9800_addr = 0b1001_0000 -- read/write is done by i2c
library
+
+
+function mcp9800_set_12_bits_temperature() return bit is
+ var bit tx_ok
+ i2c_start()
+ tx_ok = i2c_transmit_byte(mcp9800_addr)
+ tx_ok = tx_ok & i2c_transmit_byte(0b0000_0001) -- config register
address
+ tx_ok = tx_ok & i2c_transmit_byte(0b0_11_00_000) -- config register
value
+ i2c_stop()
+ return tx_ok
+end function
+
+function mcp9800_celsius() return sbyte is
+ var sdword temp
+ var byte shift_h, shift_l
+ var bit tx_ok
+ tx_ok = i2c_send_receive(mcp9800_addr, 1, 2)
+ temp = sdword(i2c_rx_buffer[0]) * 256 + i2c_rx_buffer[1]
+ temp = temp >> 4 -- last 4 bits are zero
+ temp = temp * 625
+ return sbyte(temp/10_000) -- 625/0.0625 = 10.000, works below zero
too
+end function
+
+
+function mcp9800_centicelsius() return sword is
+ var sdword temp
+ var bit tx_ok
+ var bit sign at i2c_rx_buffer[0] : 7
+ tx_ok = i2c_send_receive(mcp9800_addr, 1, 2)
+ temp = sdword(i2c_rx_buffer[0]) * 256 + i2c_rx_buffer[1]
+ if sign then
+ temp = 65536 - temp -- negative numbers in JALV2 are still a
mystery to me
+ end if
+ temp = temp >> 4 -- last 4 bits are zero
+ temp = temp * 625
+
+ if sign then
+ return -sword(temp / 100) -- 625/0.0625 = 10.000, div by 100
gives centicelsius
+ else
+ return sword(temp / 100)
+ end if
+
+end function
+
--
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