mcp4451: Add initial support for programming the mcp4451 on lpc176x

Add support for programming smoothieboard current.

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

5 files changed, 178 insertions, 1 deletions

diff --git a/config/example-extras.cfg b/config/example-extras.cfg
index 0ef6e63a..f6c9b86c 100644
--- a/config/example-extras.cfg
+++ b/config/example-extras.cfg
@@ -424,6 +424,35 @@
 #   default is to not scale the 'channel_x' parameters.
 
 
+# Statically configured MCP4451 digipot connected via I2C bus (one may
+# define any number of sections with an "mcp4451" prefix).
+#[mcp4451 my_digipot]
+#mcu: mcu
+#   The name of the micro-controller that the MCP4451 chip is
+#   connected to. The default is "mcu".
+#i2c_address:
+#   The i2c address that the chip is using on the i2c bus. This
+#   parameter must be provided.
+#wiper_0:
+#wiper_1:
+#wiper_2:
+#wiper_3:
+#   The value to statically set the given MCP4451 "wiper" to. This is
+#   typically set to a number between 0.0 and 1.0 with 1.0 being the
+#   highest resistance and 0.0 being the lowest resistance. However,
+#   the range may be changed with the 'scale' parameter (see
+#   below). If a wiper is not specified then it is left unconfigured.
+#scale:
+#   This parameter can be used to alter how the 'wiper_x' parameters
+#   are interpreted. If provided, then the 'wiper_x' parameters should
+#   be between 0.0 and 'scale'. This may be useful when the MCP4451 is
+#   used to set stepper voltage references. The 'scale' can be set to
+#   the equivalent stepper amperage if the MCP4451 were at its highest
+#   resistance, and then the 'wiper_x' parameters can be specified
+#   using the desired amperage value for the stepper. The default is
+#   to not scale the 'wiper_x' parameters.
+
+
 # Configure a TMC2130 stepper motor driver via SPI bus. To use this
 # feature, define a config section with a "tmc2130" prefix followed by
 # the name of the corresponding stepper config section (for example,
diff --git a/config/generic-smoothieboard.cfg b/config/generic-smoothieboard.cfg
index 0366e4f6..d52fff07 100644
--- a/config/generic-smoothieboard.cfg
+++ b/config/generic-smoothieboard.cfg
@@ -85,3 +85,19 @@ max_z_accel: 100
 
 [static_digital_output leds]
 pins: P1.18, P1.19, P1.20, P1.21, P4.28
+
+[mcp4451 stepper_digipot1]
+i2c_address: 88
+# Scale the config so that values can be specified in amps.
+scale: 2.25
+# wiper 0 is X (aka alpha), 1 is Y, 2 is Z, 3 is E0
+wiper_0: 1.0
+wiper_1: 1.0
+wiper_2: 1.0
+wiper_3: 1.0
+
+[mcp4451 stepper_digipot2]
+i2c_address: 90
+scale: 2.25
+# wiper 0 is E1
+wiper_0: 1.0
diff --git a/klippy/extras/mcp4451.py b/klippy/extras/mcp4451.py
new file mode 100644
index 00000000..a7eda9aa
--- /dev/null
+++ b/klippy/extras/mcp4451.py
@@ -0,0 +1,32 @@
+# MCP4451 digipot code
+#
+# Copyright (C) 2018  Kevin O'Connor <kevin@koconnor.net>
+#
+# This file may be distributed under the terms of the GNU GPLv3 license.
+import mcu
+
+WiperRegisters = [0x00, 0x01, 0x06, 0x07]
+
+class mcp4451:
+    def __init__(self, config):
+        printer = config.get_printer()
+        self.mcu = mcu.get_printer_mcu(printer, config.get('mcu', 'mcu'))
+        self.i2c_addr = config.getint('i2c_address')
+        scale = config.getfloat('scale', 1., above=0.)
+        wipers = [None]*4
+        for i in range(len(wipers)):
+            val = config.getfloat('wiper_%d' % (i,), None,
+                                  minval=0., maxval=scale)
+            if val is not None:
+                wipers[i] = int(val * 255. / scale + .5)
+        self.add_config_cmd(0x04, 0xff)
+        self.add_config_cmd(0x0a, 0xff)
+        for reg, val in zip(WiperRegisters, wipers):
+            if val is not None:
+                self.add_config_cmd(reg, val)
+    def add_config_cmd(self, reg, val):
+        self.mcu.add_config_cmd("i2c_send data=%02x%02x%02x" % (
+            self.i2c_addr, (reg << 4) | ((val >> 8) & 0x03), val), is_init=True)
+
+def load_config_prefix(config):
+    return mcp4451(config)
diff --git a/src/lpc176x/Makefile b/src/lpc176x/Makefile
index a4e3a742..e6f9007c 100644
--- a/src/lpc176x/Makefile
+++ b/src/lpc176x/Makefile
@@ -13,7 +13,7 @@ CFLAGS_klipper.elf += -T $(OUT)LPC1768.ld
 CFLAGS_klipper.elf += --specs=nano.specs --specs=nosys.specs
 
 # Add source files
-src-y += lpc176x/main.c lpc176x/timer.c lpc176x/gpio.c
+src-y += lpc176x/main.c lpc176x/timer.c lpc176x/gpio.c lpc176x/i2c.c
 src-y += generic/crc16_ccitt.c generic/alloc.c
 src-y += generic/armcm_irq.c generic/timer_irq.c
 src-y += ../lib/lpc176x/device/system_LPC17xx.c
diff --git a/src/lpc176x/i2c.c b/src/lpc176x/i2c.c
new file mode 100644
index 00000000..76c5b738
--- /dev/null
+++ b/src/lpc176x/i2c.c
@@ -0,0 +1,100 @@
+// I2C functions on lpc176x
+//
+// Copyright (C) 2018  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include "LPC17xx.h" // LPC_I2C1
+#include "board/misc.h" // timer_is_before
+#include "command.h" // DECL_COMMAND
+#include "internal.h" // gpio_peripheral
+#include "sched.h" // sched_shutdown
+
+// i2c connection status flags
+enum {
+    IF_START = 1<<5, IF_STOP = 1<<4, IF_IRQ = 1<<3, IF_ACK = 1<<2, IF_ENA = 1<<6
+};
+
+static void
+i2c_init(void)
+{
+    static int have_run_init;
+    if (have_run_init)
+        return;
+    have_run_init = 1;
+
+    // Init i2c bus 1 pins
+    gpio_peripheral(0, 0, 3, 0);
+    gpio_peripheral(0, 1, 3, 0);
+
+    // Set 100Khz frequency
+    uint32_t PCLK = SystemCoreClock / 4, pulse = PCLK / (100000 * 2);
+    LPC_I2C1->I2SCLL = pulse;
+    LPC_I2C1->I2SCLH = pulse;
+
+    // Enable interface
+    LPC_I2C1->I2CONCLR = IF_START | IF_IRQ | IF_ACK | IF_ENA;
+    LPC_I2C1->I2CONSET = IF_ENA;
+}
+
+static void
+i2c_wait(uint32_t bit, uint32_t timeout)
+{
+    for (;;) {
+        uint32_t flags = LPC_I2C1->I2CONSET;
+        if (flags & bit)
+            break;
+        if (!timer_is_before(timer_read_time(), timeout))
+            shutdown("i2c timeout");
+    }
+}
+
+static void
+i2c_start(uint32_t timeout)
+{
+    LPC_I2C1->I2CONCLR = IF_ACK | IF_IRQ | IF_START;
+    LPC_I2C1->I2CONSET = IF_ACK | IF_START;
+    i2c_wait(IF_IRQ, timeout);
+    uint32_t status = LPC_I2C1->I2STAT;
+    if (status != 0x10 && status != 0x08)
+        shutdown("Failed to send i2c start");
+    LPC_I2C1->I2CONCLR = IF_START;
+}
+
+static uint32_t
+i2c_send_byte(uint8_t b, uint32_t timeout)
+{
+    LPC_I2C1->I2DAT = b;
+    LPC_I2C1->I2CONCLR = IF_IRQ;
+    i2c_wait(IF_IRQ, timeout);
+    return LPC_I2C1->I2STAT;
+}
+
+static void
+i2c_stop(uint32_t timeout)
+{
+    LPC_I2C1->I2CONSET = IF_STOP;
+    LPC_I2C1->I2CONCLR = IF_IRQ;
+    i2c_wait(IF_STOP, timeout);
+}
+
+static void
+i2c_send(uint8_t *data, int data_len)
+{
+    i2c_init();
+    uint32_t timeout = timer_read_time() + timer_from_us(5000);
+
+    i2c_start(timeout);
+    while (data_len--)
+        i2c_send_byte(*data++, timeout);
+    i2c_stop(timeout);
+}
+
+// This provides just enough functionality to program an MCP4451 chip
+void
+command_i2c_send(uint32_t *args)
+{
+    uint8_t data_len = args[0], *data = (void*)(size_t)args[1];
+    i2c_send(data, data_len);
+}
+DECL_COMMAND(command_i2c_send, "i2c_send data=%*s");