Add config options to enable onboard i2c pull-ups

* CIRCUITPY_BUSIO_I2C_INTERNAL_PULLUPS config option to enable/use internal i2c pull-ups.
* CIRCUITPY_BUSIO_I2C_INTERNAL_PULLUPS_AVAILABLE to indicate availability of internal pull-up resistors.
* Add a check to ensure onboard pullups are available when requested.
* Enable onboard pullups for pimoroni_keybow2040
* Indicate onboard pullups are available on Pico
* NB: Onboard pullups are weak and not ideal

Author: Gadgetoid

ports/raspberrypi/boards/pimoroni_keybow2040/mpconfigboard.h

@@ -39,3 +39,4 @@
 #define IGNORE_PIN_GPIO27   1
 #define IGNORE_PIN_GPIO28   1
 #define IGNORE_PIN_GPIO29   1
+

ports/raspberrypi/boards/pimoroni_keybow2040/mpconfigboard.mk

@@ -9,3 +9,6 @@ CHIP_FAMILY = rp2
 INTERNAL_FLASH_FILESYSTEM = 1
 
 CIRCUITPY__EVE = 1
+
+CIRCUITPY_REQUIRE_I2C_PULLUPS ?= 0
+CIRCUITPY_BUSIO_I2C_INTERNAL_PULLUPS ?= 1

ports/raspberrypi/common-hal/busio/I2C.c

@@ -108,8 +108,10 @@ void common_hal_busio_i2c_construct(busio_i2c_obj_t *self,
     // set up as GPIO by the bitbangio.I2C object.
     //
     // Sets pins to open drain, high, and input.
+#ifndef CIRCUITPY_BUSIO_I2C_INTERNAL_PULLUPS
     shared_module_bitbangio_i2c_construct(&self->bitbangio_i2c, scl, sda,
-        frequency, timeout);
+                                          frequency, timeout);
+#endif
 
     self->baudrate = i2c_init(self->peripheral, frequency);
 
@@ -120,6 +122,11 @@ void common_hal_busio_i2c_construct(busio_i2c_obj_t *self,
 
     gpio_set_function(self->scl_pin, GPIO_FUNC_I2C);
     gpio_set_function(self->sda_pin, GPIO_FUNC_I2C);
+
+#if CIRCUITPY_BUSIO_I2C_INTERNAL_PULLUPS
+    gpio_set_pulls(self->scl_pin, true, false);
+    gpio_set_pulls(self->sda_pin, true, false);
+#endif
 }
 
 bool common_hal_busio_i2c_deinited(busio_i2c_obj_t *self) {
@@ -163,6 +170,8 @@ void common_hal_busio_i2c_unlock(busio_i2c_obj_t *self) {
 
 uint8_t common_hal_busio_i2c_write(busio_i2c_obj_t *self, uint16_t addr,
                                    const uint8_t *data, size_t len, bool transmit_stop_bit) {
+
+#ifndef CIRCUITPY_BUSIO_I2C_INTERNAL_PULLUPS
     if (len == 0) {
         // The RP2040 I2C peripheral will not perform 0 byte writes.
         // So use bitbangio.I2C to do the write.
@@ -184,6 +193,7 @@ uint8_t common_hal_busio_i2c_write(busio_i2c_obj_t *self, uint16_t addr,
 
         return status;
     }
+#endif
 
     int result = i2c_write_timeout_us(self->peripheral, addr, data, len, !transmit_stop_bit, BUS_TIMEOUT_US);
     if (result == len) {

ports/raspberrypi/mpconfigport.mk

@@ -23,6 +23,8 @@ else
 CIRCUITPY_NEOPIXEL_WRITE = 0
 endif
 
+CIRCUITPY_BUSIO_I2C_INTERNAL_PULLUPS_AVAILABLE ?= 1
+
 CIRCUITPY_FRAMEBUFFERIO = 1
 CIRCUITPY_FULL_BUILD = 1
 CIRCUITPY_AUDIOMP3 ?= 1

py/circuitpy_mpconfig.h

@@ -314,6 +314,11 @@ extern const struct _mp_obj_module_t bitmaptools_module;
 #define BITMAPTOOLS_MODULE
 #endif
 
+#if CIRCUITPY_BUSIO_I2C_INTERNAL_PULLUPS && !CIRCUITPY_BUSIO_I2C_INTERNAL_PULLUPS_AVAILABLE
+#error "CIRCUITPY_BUSIO_I2C_INTERNAL_PULLUPS requires onboard pullups." \
+       "Ensure board supports these and set CIRCUITPY_BUSIO_I2C_INTERNAL_PULLUPS_AVAILABLE = 1"
+#endif
+
 #if CIRCUITPY_BITOPS
 extern const struct _mp_obj_module_t bitops_module;
 #define BITOPS_MODULE        { MP_OBJ_NEW_QSTR(MP_QSTR_bitops),(mp_obj_t)&bitops_module },

py/circuitpy_mpconfig.mk

@@ -121,6 +121,12 @@ CFLAGS += -DCIRCUITPY_BUILTINS_POW3=$(CIRCUITPY_BUILTINS_POW3)
 CIRCUITPY_BUSIO ?= 1
 CFLAGS += -DCIRCUITPY_BUSIO=$(CIRCUITPY_BUSIO)
 
+CIRCUITPY_BUSIO_I2C_INTERNAL_PULLUPS ?= 0
+CFLAGS += -DCIRCUITPY_BUSIO_I2C_INTERNAL_PULLUPS=$(CIRCUITPY_BUSIO_I2C_INTERNAL_PULLUPS)
+
+CIRCUITPY_BUSIO_I2C_INTERNAL_PULLUPS_AVAILABLE ?= 0
+CFLAGS += -DCIRCUITPY_BUSIO_I2C_INTERNAL_PULLUPS_AVAILABLE=$(CIRCUITPY_BUSIO_I2C_INTERNAL_PULLUPS_AVAILABLE)
+
 CIRCUITPY_CAMERA ?= 0
 CFLAGS += -DCIRCUITPY_CAMERA=$(CIRCUITPY_CAMERA)