ports/mega: Add bare i2c API to mega port

Get/put register values to any i2c device.

Signed-off-by: Keith Packard <keithp@keithp.com>

ports/mega/Makefile

@@ -23,6 +23,8 @@ SNEK_LOCAL_SRC = \
 	$(SNEK_ATMEGA_SRC) \
 	$(SNEK_ATMEGA_MATH_SRC) \
 	snek-input.c \
+	snek-i2c.c \
+	snek-atmega-i2c.c \
 	snek-mega.c
 
 SNEK_LOCAL_INC = \
@@ -34,6 +36,7 @@ SNEK_LOCAL_BUILTINS = \
 	$(SNEK_ATMEGA_MATH_BUILTINS) \
 	snek-math.builtin \
 	snek-input.builtin \
+	snek-i2c.builtin \
 	snek-mega.builtin
 
 include $(SNEK_ROOT)/snek-install.defs

snek-i2c.builtin

@@ -0,0 +1,17 @@
+#
+# Copyright © 2031 Keith Packard <keithp@keithp.com>
+#
+# 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 3 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.
+#
+# Low-level I2C functions
+#
+i2c.put, 3
+i2c.get, 2

snek-i2c.c

@@ -0,0 +1,47 @@
+/*
+ * Copyright © 2021 Keith Packard <keithp@keithp.com>
+ *
+ * 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 3 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.
+ */
+
+#include "snek.h"
+#include "snek-i2c.h"
+
+snek_poly_t
+snek_builtin_i2c_put(snek_poly_t addr, snek_poly_t reg, snek_poly_t val)
+{
+	uint8_t iaddr = snek_poly_get_soffset(addr);
+	uint8_t ireg = snek_poly_get_soffset(reg);
+	uint8_t ival = snek_poly_get_soffset(val);
+
+	if (snek_abort)
+		return SNEK_NULL;
+
+	snek_i2c_put(iaddr, ireg, ival);
+	return SNEK_NULL;
+}
+
+snek_poly_t
+snek_builtin_i2c_get(snek_poly_t addr, snek_poly_t reg)
+{
+	uint8_t iaddr = snek_poly_get_soffset(addr);
+	uint8_t ireg = snek_poly_get_soffset(reg);
+
+	if (snek_abort)
+		return SNEK_NULL;
+
+	uint8_t ival = snek_i2c_get(iaddr, ireg);
+	return snek_soffset_to_poly(ival);
+}