mcp4018: Add initial support for the mcp4018 digipot

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

1 files changed, 81 insertions, 0 deletions

diff --git a/klippy/extras/mcp4018.py b/klippy/extras/mcp4018.py
new file mode 100644
index 00000000..f53024b9
--- /dev/null
+++ b/klippy/extras/mcp4018.py
@@ -0,0 +1,81 @@
+# MCP4018 digipot support (via bit-banging)
+#
+# Copyright (C) 2019  Kevin O'Connor <kevin@koconnor.net>
+#
+# This file may be distributed under the terms of the GNU GPLv3 license.
+
+class SoftwareI2C:
+    def __init__(self, config, addr):
+        self.addr = addr << 1
+        self.update_pin_cmd = None
+        # Lookup pins
+        ppins = config.get_printer().lookup_object('pins')
+        scl_pin = config.get('scl_pin')
+        scl_params = ppins.lookup_pin(scl_pin, share_type='sw_scl')
+        self.mcu = scl_params['chip']
+        self.scl_pin = scl_params['pin']
+        self.scl_main = scl_params.get('class')
+        if self.scl_main is None:
+            self.scl_main = scl_params['class'] = self
+            self.scl_oid = self.mcu.create_oid()
+            self.cmd_queue = self.mcu.alloc_command_queue()
+            self.mcu.register_config_callback(self.build_config)
+        else:
+            self.scl_oid = self.scl_main.scl_oid
+            self.cmd_queue = self.scl_main.cmd_queue
+        sda_params = ppins.lookup_pin(config.get('sda_pin'))
+        self.sda_oid = self.mcu.create_oid()
+        if sda_params['chip'] != self.mcu:
+            raise ppins.error("%s: scl_pin and sda_pin must be on same mcu" % (
+                config.get_name(),))
+        self.mcu.add_config_cmd("config_digital_out oid=%d pin=%s"
+                                " value=%d default_value=%d max_duration=%d" % (
+                                    self.sda_oid, sda_params['pin'], 1, 1, 0))
+    def build_config(self):
+        self.mcu.add_config_cmd("config_digital_out oid=%d pin=%s value=%d"
+                                " default_value=%d max_duration=%d" % (
+                                    self.scl_oid, self.scl_pin, 1, 1, 0))
+        self.update_pin_cmd = self.mcu.lookup_command(
+            "update_digital_out oid=%c value=%c", cq=self.cmd_queue)
+    def i2c_write(self, msg):
+        msg = [self.addr] + msg
+        send = self.scl_main.update_pin_cmd.send
+        # Send ack
+        send([self.sda_oid, 0])
+        send([self.scl_oid, 0])
+        # Send bytes
+        sda_last = 0
+        for data in msg:
+            # Transmit 8 data bits
+            for i in range(8):
+                sda_next = not not (data & (0x80 >> i))
+                if sda_last != sda_next:
+                    sda_last = sda_next
+                    send([self.sda_oid, sda_last])
+                send([self.scl_oid, 1])
+                send([self.scl_oid, 0])
+            # Transmit clock for ack
+            send([self.scl_oid, 1])
+            send([self.scl_oid, 0])
+        # Send stop
+        if sda_last:
+            send([self.sda_oid, 0])
+        send([self.scl_oid, 1])
+        send([self.sda_oid, 1])
+
+class mcp4018:
+    def __init__(self, config):
+        self.i2c = SoftwareI2C(config, 0x2f)
+        self.scale = config.getfloat('scale', 1., above=0.)
+        self.start_value = config.getfloat('wiper',
+                                           minval=0., maxval=self.scale)
+        config.get_printer().register_event_handler("klippy:connect",
+                                                    self.handle_connect)
+    def handle_connect(self):
+        self.set_dac(self.start_value)
+    def set_dac(self, value):
+        val = int(value * 127. / self.scale + .5)
+        self.i2c.i2c_write([val])
+
+def load_config_prefix(config):
+    return mcp4018(config)