srd: Add National LM75 protocol decoder.

This shall support the original National LM75 I2C-based temperature sensor,
as well as various compatible devices of other vendors, such as the
Fairchild FM75, Dallas DS75, and so on.

Currently only 9bit resolution is supported, and not all commands are
decoded, yet. The register contents and temperatures are decoded
correctly though, and can be output in both Celsius and Kelvin.

1 files changed, 218 insertions, 0 deletions

diff --git a/decoders/lm75/lm75.py b/decoders/lm75/lm75.py
new file mode 100644
index 0000000..8a06412
--- /dev/null
+++ b/decoders/lm75/lm75.py
@@ -0,0 +1,218 @@
+##
+## This file is part of the sigrok project.
+##
+## Copyright (C) 2012 Uwe Hermann <uwe@hermann-uwe.de>
+##
+## This program is free software; you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 2 of the License, or
+## (at your option) any later version.
+##
+## This program is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with this program; if not, write to the Free Software
+## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
+##
+
+# National LM75 (and compatibles) temperature sensor protocol decoder
+
+# TODO: Better support for various LM75 compatible devices.
+
+import sigrokdecode as srd
+
+# LM75 only supports 9 bit resolution, compatible devices usually 9-12 bits.
+resolution = {
+    # CONFIG[6:5]: <resolution>
+    0x00: 9,
+    0x01: 10,
+    0x02: 11,
+    0x03: 12,
+}
+
+ft = {
+    # CONFIG[4:3]: <fault tolerance setting>
+    0x00: 1,
+    0x01: 2,
+    0x02: 4,
+    0x03: 6,
+}
+
+class Decoder(srd.Decoder):
+    api_version = 1
+    id = 'lm75'
+    name = 'LM75'
+    longname = 'National LM75'
+    desc = 'National LM75 (and compatibles) temperature sensor protocol.'
+    license = 'gplv2+'
+    inputs = ['i2c']
+    outputs = ['lm75']
+    probes = []
+    optional_probes = [
+        {'id': 'os', 'name': 'OS', 'desc': 'Overtemperature shutdown'},
+        {'id': 'a0', 'name': 'A0', 'desc': 'I2C slave address input 0'},
+        {'id': 'a1', 'name': 'A1', 'desc': 'I2C slave address input 1'},
+        {'id': 'a2', 'name': 'A2', 'desc': 'I2C slave address input 2'},
+    ]
+    options = {
+        'sensor': ['Sensor type', 'lm75'],
+        'resolution': ['Resolution', 9], # 9-12 bit, sensor/config dependent
+    }
+    annotations = [
+        ['Celsius', 'Temperature in degrees Celsius'],
+        ['Kelvin', 'Temperature in degrees Kelvin'],
+        ['Text (verbose)', 'Human-readable text (verbose)'],
+        ['Text', 'Human-readable text'],
+        ['Warnings', 'Human-readable warnings'],
+    ]
+
+    def __init__(self, **kwargs):
+        self.state = 'IDLE'
+        self.reg = 0x00 # Currently selected register
+        self.databytes = []
+        self.mintemp = 0
+        self.maxtemp = 0
+        self.avgtemp = 0
+
+    def start(self, metadata):
+        # self.out_proto = self.add(srd.OUTPUT_PROTO, 'lm75')
+        self.out_ann = self.add(srd.OUTPUT_ANN, 'lm75')
+
+    def report(self):
+        # TODO: Output min/max/avg temperature.
+        pass
+
+    def putx(self, data):
+        # Helper for annotations which span exactly one I2C packet.
+        self.put(self.ss, self.es, self.out_ann, data)
+
+    def putb(self, data):
+        # Helper for annotations which span a block of I2C packets.
+        self.put(self.block_start, self.block_end, self.out_ann, data)
+
+    def warn_upon_invalid_slave(self, addr):
+        # LM75 and compatible devices have a 7-bit I2C slave address where
+        # the 4 MSBs are fixed to 1001, and the 3 LSBs are configurable.
+        # Thus, valid slave addresses (1001xxx) range from 0x48 to 0x4f.
+        if addr not in range(0x48, 0x4f + 1):
+            s = 'Warning: I2C slave 0x%02x not an LM75 compatible sensor.'
+            self.putx([4, [s % addr]])
+
+    def output_temperature(self, s):
+        # TODO: Support for resolutions other than 9 bit.
+        before, after = self.databytes[0], (self.databytes[1] >> 7) * 5
+        celsius = float('%d.%d' % (before, after))
+        kelvin = celsius + 273.15
+        self.putb([0, ['%s: %.1f °C' % (s, celsius)]])
+        self.putb([1, ['%s: %.1f °K' % (s, kelvin)]])
+
+        # Keep some statistics. Can be output in report(), for example.
+        if celsius < self.mintemp:
+            self.mintemp = celsius
+        if celsius > self.maxtemp:
+            self.maxtemp = celsius
+        # TODO: avg. temp.
+
+    def handle_temperature_reg(self, b, s):
+        # Common helper for the temperature/T_HYST/T_OS registers.
+        if len(self.databytes) == 0:
+            self.block_start = self.ss
+            self.databytes.append(b)
+            return
+        self.databytes.append(b)
+        self.block_end = self.es
+        self.output_temperature(s)
+        self.databytes = []
+
+    def handle_reg_0x00(self, b):
+        # Temperature register (16bits, read-only).
+        self.handle_temperature_reg(b, 'Temperature')
+
+    def handle_reg_0x01(self, b):
+        # Configuration register (8 bits, read/write).
+        # TODO: Bit-exact annotation ranges.
+
+        sd = b & (1 << 0)
+        tmp = 'normal operation' if (sd == 0) else 'shutdown mode'
+        s = 'SD = %d: %s\n' % (sd, tmp)
+        s2 = 'SD = %s, ' % tmp
+
+        cmp_int = b & (1 << 1)
+        tmp = 'comparator' if (cmp_int == 0) else 'interrupt'
+        s += 'CMP/INT = %d: %s mode\n' % (cmp_int, tmp)
+        s2 += 'CMP/INT = %s, ' % tmp
+
+        pol = b & (1 << 2)
+        tmp = 'low' if (pol == 0) else 'high'
+        s += 'POL = %d: OS polarity is active-%s\n' % (pol, tmp)
+        s2 += 'POL = active-%s, ' % tmp
+
+        bits = (b & ((1 << 4) | (1 << 3))) >> 3
+        s += 'Fault tolerance setting: %d bit(s)\n' % ft[bits]
+        s2 += 'FT = %d' % ft[bits]
+
+        # Not supported by LM75, but by various compatible devices.
+        if self.options['sensor'] != 'lm75': # TODO
+            bits = (b & ((1 << 6) | (1 << 5))) >> 5
+            s += 'Resolution: %d bits\n' % resolution[bits]
+            s2 += ', resolution = %d' % resolution[bits]
+
+        self.putx([2, [s]])
+        self.putx([3, [s2]])
+
+    def handle_reg_0x02(self, b):
+        # T_HYST register (16 bits, read/write).
+        self.handle_temperature_reg(b, 'T_HYST trip temperature')
+
+    def handle_reg_0x03(self, b):
+        # T_OS register (16 bits, read/write).
+        self.handle_temperature_reg(b, 'T_OS trip temperature')
+
+    def handle_reg_write(self, b):
+        # TODO
+        self.putx([0, ['LM75 write: reg 0x%02x = 0x%02x' % (self.reg, b)]])
+
+    def decode(self, ss, es, data):
+        cmd, databyte = data
+
+        # Store the start/end samples of this I2C packet.
+        self.ss, self.es = ss, es
+
+        # State machine.
+        if self.state == 'IDLE':
+            # Wait for an I2C START condition.
+            if cmd != 'START':
+                return
+            self.state = 'GET SLAVE ADDR'
+        elif self.state == 'GET SLAVE ADDR':
+            # Wait for an address read/write operation.
+            if cmd == 'ADDRESS READ':
+                self.warn_upon_invalid_slave(databyte)
+                self.state = 'READ REGS'
+            elif cmd == 'ADDRESS WRITE':
+                self.state = 'WRITE REGS'
+        elif self.state == 'READ REGS':
+            if cmd == 'DATA READ':
+                handle_reg = getattr(self, 'handle_reg_0x%02x' % self.reg)
+                handle_reg(databyte)
+            elif cmd == 'STOP':
+                # TODO: Any output?
+                self.state = 'IDLE'
+            else:
+                # self.putx([0, ['Ignoring: %s (data=%s)' % (cmd, databyte)]])
+                pass
+        elif self.state == 'WRITE REGS':
+            if cmd == 'DATA WRITE':
+                self.handle_reg_write(databyte)
+            elif cmd == 'STOP':
+                # TODO: Any output?
+                self.state = 'IDLE'
+            else:
+                # self.putx([0, ['Ignoring: %s (data=%s)' % (cmd, databyte)]])
+                pass
+        else:
+            raise Exception('Invalid state: %s' % self.state)
+