Merge pull request #104 from diijkstra/i2c_gpio

Advanced I2C SFP pins definition

Makefile

@@ -21,7 +21,7 @@ all: create_build_dir $(VERSION_HEADER) $(SUBDIRS) $(BUILDDIR)rtlplayground.bin
 create_build_dir:
 	mkdir -p $(BUILDDIR)
 
-SRCS = rtlplayground.c rtl837x_flash.c rtl837x_phy.c rtl837x_port.c cmd_parser.c html_data.c rtl837x_igmp.c rtl837x_stp.c dhcp.c  machine.c
+SRCS = rtlplayground.c rtl837x_flash.c rtl837x_phy.c rtl837x_port.c cmd_parser.c html_data.c rtl837x_igmp.c rtl837x_stp.c rtl837x_pins.c dhcp.c machine.c
 OBJS = ${SRCS:%.c=$(BUILDDIR)%.rel}
 OBJS += uip/$(BUILDDIR)/timer.rel uip/$(BUILDDIR)/uip-fw.rel uip/$(BUILDDIR)/uip-neighbor.rel uip/$(BUILDDIR)/uip-split.rel uip/$(BUILDDIR)/uip.rel uip/$(BUILDDIR)/uip_arp.rel uip/$(BUILDDIR)/uiplib.rel httpd/$(BUILDDIR)/httpd.rel httpd/$(BUILDDIR)/page_impl.rel
 

httpd/page_impl.c

@@ -5,6 +5,7 @@
 #include "rtl837x_regs.h"
 #include "rtl837x_port.h"
 #include "rtl837x_flash.h"
+#include "rtl837x_pins.h"
 #include "uip.h"
 #include "html_data.h"
 #include <stdint.h>
@@ -178,7 +179,7 @@ void sfp_send_data(uint8_t slot, uint8_t reg, uint8_t len)
 	}
 
 	reg_read_m(RTL837X_REG_I2C_CTRL);
-	sfr_mask_data(1, 0xfc, machine.sfp_port[slot].i2c == 0 ? SCL_PIN << 5 | SDA_PIN_0 << 2 : SCL_PIN << 5 | SDA_PIN_1 << 2 );
+	sfr_mask_data(1, 0xfc, i2c_bus_from_scl_pin(machine.sfp_port[slot].i2c.scl) << 5 | i2c_bus_from_sda_pin(machine.sfp_port[slot].i2c.sda) << 2);
 	reg_write_m(RTL837X_REG_I2C_CTRL);
 
 	REG_WRITE(RTL837X_REG_I2C_IN, 0, 0, 0, reg);

machine.c

@@ -1,4 +1,5 @@
 #include "machine.h"
+#include "rtl837x_pins.h"
 
 #ifdef MACHINE_KP_9000_6XHML_X2
 __code const struct machine machine = {
@@ -10,15 +11,17 @@ __code const struct machine machine = {
 	.log_to_phys_port = {0, 0, 0, 5, 1, 2, 3, 4, 6},
 	.phys_to_log_port = {4, 5, 6, 7, 3, 8, 0, 0, 0},
 	.is_sfp = {0, 0, 0, 2, 0, 0, 0, 0, 1},
-	.sfp_port[0].pin_detect = 50,
+	.sfp_port[0].pin_detect = GPIO50_I2C_SCL2_UART1_TX,
-	.sfp_port[0].pin_los = 10,
+	.sfp_port[0].pin_los = GPIO10_LED10,
+	.sfp_port[0].pin_tx_disable = GPIO_NA,
 	.sfp_port[0].sds = 1,
-	.sfp_port[0].i2c = 1,
+	.sfp_port[0].i2c = { .sda = GPIO41_I2C_SDA3_MDIO1, .scl = GPIO40_I2C_SCL3_MDC1 },
-	.sfp_port[1].pin_detect = 30,
+	.sfp_port[1].pin_detect = GPIO30_ACL_BIT3_EN,
-	.sfp_port[1].pin_los = 37,
+	.sfp_port[1].pin_los = GPIO37,
+	.sfp_port[1].pin_tx_disable = GPIO_NA,
 	.sfp_port[1].sds = 0,
-	.sfp_port[1].i2c = 0,
+	.sfp_port[1].i2c = { .sda = GPIO39_I2C_SDA4, .scl = GPIO40_I2C_SCL3_MDC1 },
-	.reset_pin = 46,
+	.reset_pin = GPIO46_I2C_SCL0,
 };
 #elif defined MACHINE_KP_9000_6XH_X
 __code const struct machine machine = {
@@ -30,10 +33,12 @@ __code const struct machine machine = {
 	.log_to_phys_port = {0, 0, 0, 5, 1, 2, 3, 4, 6},
 	.phys_to_log_port = {4, 5, 6, 7, 3, 8, 0, 0, 0},
 	.is_sfp = {0, 0, 0, 0, 0, 0, 0, 0, 1},
-	.sfp_port[0].pin_detect = 30,
+	.sfp_port[0].pin_detect = GPIO30_ACL_BIT3_EN,
-	.sfp_port[0].pin_los = 37,
+	.sfp_port[0].pin_los = GPIO37,
+	.sfp_port[0].pin_tx_disable = GPIO_NA,
 	.sfp_port[0].sds = 1,
-	.sfp_port[0].i2c = 0,
+	.sfp_port[0].i2c = { .sda = GPIO39_I2C_SDA4, .scl = GPIO40_I2C_SCL3_MDC1 },
+	.reset_pin = GPIO_NA,
 };
 #elif defined MACHINE_KP_9000_9XH_X_EU
 __code const struct machine machine = {
@@ -45,11 +50,14 @@ __code const struct machine machine = {
 	.log_to_phys_port = {1, 2, 3, 4, 5, 6, 7, 8, 9},
 	.phys_to_log_port = {0, 1, 2, 3, 4, 5, 6, 7, 8},
 	.is_sfp = {0, 0, 0, 0, 0, 0, 0, 0, 1},
-	.sfp_port[0].pin_detect = 30,
+	.sfp_port[0].pin_detect = GPIO30_ACL_BIT3_EN,
-	.sfp_port[0].pin_los = 37,
+	.sfp_port[0].pin_los = GPIO37,
+	.sfp_port[0].pin_tx_disable = GPIO_NA,
 	.sfp_port[0].sds = 1,
-	.sfp_port[0].i2c = 0,
+	.sfp_port[0].i2c = { .sda = GPIO39_I2C_SDA4, .scl = GPIO40_I2C_SCL3_MDC1 },
+	.reset_pin = GPIO_NA,
 };
+
 #elif defined MACHINE_SWGT024_V2_0
 __code const struct machine machine = {
 	.machine_name = "SWGT024 V2.0",
@@ -61,17 +69,20 @@ __code const struct machine machine = {
 	.phys_to_log_port = {4, 5, 6, 7, 8, 3, 0, 0, 0},
 	.is_sfp= {0, 0, 0, 2, 0, 0, 0, 0, 1},
 	// Left SFP port (J4)
-	.sfp_port[0].pin_detect = 30,
+	.sfp_port[0].pin_detect = GPIO30_ACL_BIT3_EN,
-	.sfp_port[0].pin_los = 37,
+	.sfp_port[0].pin_los = GPIO37,
+	.sfp_port[0].pin_tx_disable = GPIO_NA,
 	.sfp_port[0].sds = 1,
-	.sfp_port[0].i2c = 0, /* GPIO 39 */
+	.sfp_port[0].i2c = { .sda = GPIO39_I2C_SDA4, .scl = GPIO40_I2C_SCL3_MDC1 }, /* GPIO 39 */
 	// Right SFP port (J2)
-	.sfp_port[1].pin_detect = 50,
+	.sfp_port[1].pin_detect = GPIO50_I2C_SCL2_UART1_TX,
-	.sfp_port[1].pin_los = 51,
+	.sfp_port[1].pin_los = GPIO51_I2C_SDA2_UART1_RX,
+	.sfp_port[1].pin_tx_disable = GPIO_NA,
 	.sfp_port[1].sds = 0,
-	.sfp_port[1].i2c = 1, /* GPIO 40 */
+	.sfp_port[1].i2c = { .sda = GPIO41_I2C_SDA3_MDIO1, .scl = GPIO40_I2C_SCL3_MDC1 }, /* GPIO 40 */
-	.reset_pin = 36,
+	.reset_pin = GPIO36_PWM_OUT,
 };
+
 #elif defined DEFAULT_8C_1SFP
 __code const struct machine machine = {
 	.machine_name = "8+1 SFP Port Switch",
@@ -82,10 +93,11 @@ __code const struct machine machine = {
 	.log_to_phys_port = {1, 2, 3, 4, 5, 6, 7, 8, 9},
 	.phys_to_log_port = {0, 1, 2, 3, 4, 5, 6, 7, 8},
 	.is_sfp = {0, 0, 0, 0, 0, 0, 0, 0, 1},
-	.sfp_port[0].pin_detect = 30,
+	.sfp_port[0].pin_detect = GPIO30_ACL_BIT3_EN,
-	.sfp_port[0].pin_los = 37,
+	.sfp_port[0].pin_los = GPIO37,
+	.sfp_port[0].pin_tx_disable = GPIO_NA,
 	.sfp_port[0].sds = 1,
-	.sfp_port[0].i2c = 0,
+	.sfp_port[0].i2c = { .sda = GPIO39_I2C_SDA4, .scl = GPIO40_I2C_SCL3_MDC1 },
+	.reset_pin = GPIO_NA,
 };
-
 #endif

machine.h

@@ -16,12 +16,19 @@
 
 // #define DEFAULT_5C_1SFP
 
+typedef struct {
+	// GPIO pins for SDA/SCL
+	uint8_t sda; 
+	uint8_t scl;
+} i2c_bus_t;
+
 struct sfp_port
 {
 	uint8_t pin_detect; // gpio number 0-63, 0xFF = don't have it?
 	uint8_t pin_los; // gpio number 0-63, 0xFF = don't have it?
+	uint8_t pin_tx_disable; // gpio number 0-63, 0xFF = not present
 	uint8_t sds;
-	uint8_t i2c;
+	i2c_bus_t i2c;
 };
 
 typedef struct machine {

rtl837x_common.h

@@ -7,11 +7,6 @@
 
 #define SYS_TICK_HZ 200
 
-// SCL and SDA pin numbers for SFP cage 0 and SFP cage 1
-#define SCL_PIN		3
-#define SDA_PIN_0	4
-#define SDA_PIN_1	3
-
 #define CPU_PORT        9
 
 // Define Port-masks for 9-port devices and 6-port devices

rtl837x_pins.c

@@ -0,0 +1,120 @@
+#include "rtl837x_pins.h"
+#include "rtl837x_common.h"
+#include "rtl837x_regs.h"
+
+uint8_t i2c_bus_from_sda_pin(uint8_t sda_pin) {
+	switch (sda_pin) {
+		case GPIO47_I2C_SDA0:
+			return 0;
+		case GPIO49_I2C_SDA1:
+			return 1;
+		case GPIO51_I2C_SDA2_UART1_RX:
+			return 2;
+		case GPIO41_I2C_SDA3_MDIO1:
+			return 3;
+		case GPIO39_I2C_SDA4:
+			return 4;
+		default:
+			return 0xFF;
+	}
+}
+
+uint8_t i2c_bus_from_scl_pin(uint8_t scl_pin) {
+	switch (scl_pin) {
+		case GPIO46_I2C_SCL0:
+			return 0;
+		case GPIO48_I2C_SCL1:
+			return 1;
+		case GPIO50_I2C_SCL2_UART1_TX:
+			return 2;
+		case GPIO40_I2C_SCL3_MDC1:
+			return 3;
+		default:
+			return 0xFF;
+	}
+}
+
+/* Returns RTL837X_REG_GPIO_XX_OUTPUT register address */
+static uint16_t gpio_output_reg(uint8_t pin) {
+	return pin < 32 ? RTL837X_REG_GPIO_00_31_OUTPUT : RTL837X_REG_GPIO_32_63_OUTPUT;
+} 
+
+/* Returns RTL837X_REG_GPIO_XX_DIRECTION register address */
+static uint16_t gpio_direction_reg(uint8_t pin) {
+	return pin < 32 ? RTL837X_REG_GPIO_00_31_DIRECTION : RTL837X_REG_GPIO_32_63_DIRECTION;
+} 
+
+
+/* Enable GPIO functions for pin */
+static void gpio_mux_setup(uint8_t pin)
+{
+	// Some GPIOs require setting MUX registers to enable GPIO
+	switch (pin) {
+		case GPIO10_LED10:
+			reg_bit_clear(RTL837X_PIN_MUX_0, 10);
+			break;
+		case GPIO30_ACL_BIT3_EN:
+			reg_bit_clear(RTL837X_PIN_MUX_2, 3);
+			break;
+		case GPIO36_PWM_OUT:
+			reg_bit_set(RTL837X_PIN_MUX_1, 30);
+			break;
+		case GPIO37:
+		case GPIO38:
+			// Intentionally empty, always GPIO
+			break;
+		case GPIO46_I2C_SCL0:
+			// Bit 7-8 0b00 -> GPIO
+			reg_read_m(RTL837X_PIN_MUX_1);
+			sfr_mask_data(0, 0x80, 0x00);
+			sfr_mask_data(1, 0x01, 0x00);
+			reg_write_m(RTL837X_PIN_MUX_1);	
+			break;
+		case GPIO50_I2C_SCL2_UART1_TX:
+			// Bit 15-16 0b00 -> GPIO
+			reg_read_m(RTL837X_PIN_MUX_1);
+			sfr_mask_data(1, 0x80, 0x00);
+			sfr_mask_data(2, 0x01, 0x00);
+			reg_write_m(RTL837X_PIN_MUX_1);	
+			break;
+		case GPIO51_I2C_SDA2_UART1_RX:
+			// Bit 17-18 0b00 -> GPIO
+			reg_read_m(RTL837X_PIN_MUX_1);
+			sfr_mask_data(2, 0x06, 0x00);
+			reg_write_m(RTL837X_PIN_MUX_1);
+			break;
+		case GPIO54_ACL_BIT2_EN:
+			reg_bit_clear(RTL837X_PIN_MUX_2, 2);
+			break;
+		case GPIO_NA:
+			print_string("Attemped to assign GPIO function to N/A pin!");
+			break;
+		default:
+			print_string("GPIO MUX setup not implemented for pin="); print_byte(pin); print_string("\n");
+	}
+}
+
+void gpio_input_setup(uint8_t pin) {
+	if (pin == GPIO_NA) { 
+		return;
+	}
+
+	gpio_mux_setup(pin);
+	reg_bit_clear(gpio_direction_reg(pin), (pin % 32));
+}
+
+void gpio_output_setup(uint8_t pin, __xdata uint8_t initial_val) {
+	if (pin == GPIO_NA) { 
+		return;
+	}
+	gpio_mux_setup(pin);
+
+	// We need to setup value before enabling output on PIN
+	if (initial_val) {
+		reg_bit_set(gpio_output_reg(pin), (pin % 32));
+	} else {
+		reg_bit_clear(gpio_output_reg(pin), (pin % 32));
+	}
+
+	reg_bit_set(gpio_direction_reg(pin), (pin % 32));
+}

rtl837x_pins.h

@@ -0,0 +1,93 @@
+#ifndef _RTL837X_PINS_H_
+#define _RTL837X_PINS_H_
+
+#include <stdint.h>
+
+#define GPIO0_LED0                0
+#define GPIO1_LED1                1
+#define GPIO2_LED2                2
+#define GPIO3_LED3                3
+#define GPIO4_LED4                4
+#define GPIO5_LED5                5
+#define GPIO6_LED6                6
+#define GPIO7_LED7                7
+#define GPIO8_LED8                8
+#define GPIO9_LED9                9
+#define GPIO10_LED10              10
+#define GPIO11_LED11              11
+#define GPIO12_LED12              12
+#define GPIO13_LED13              13
+#define GPIO14_LED14              14
+#define GPIO15_LED15              15
+#define GPIO16_LED16              16
+#define GPIO17_LED17              17
+#define GPIO18_LED18              18
+#define GPIO19_LED19              19
+#define GPIO20_LED20              20
+#define GPIO21_LED21              21
+#define GPIO22_LED22              22
+#define GPIO23_LED23              23
+#define GPIO24_LED24              24
+#define GPIO25_LED25              25
+#define GPIO26_LED26              26
+#define GPIO27_LED27              27
+#define GPIO28_SYS_LED            28
+#define GPIO29_GLB_RLDP_LED_EN    29
+#define GPIO30_ACL_BIT3_EN        30
+#define GPIO31_UART0_TX           31
+#define GPIO32_UART0_RX           32
+#define GPIO33_INT                33
+#define GPIO34_MDC0               34
+#define GPIO35_MDIO0              35
+#define GPIO36_PWM_OUT            36
+#define GPIO37                    37
+#define GPIO38                    38
+#define GPIO39_I2C_SDA4           39
+#define GPIO40_I2C_SCL3_MDC1      40
+#define GPIO41_I2C_SDA3_MDIO1     41
+#define GPIO42_SPI                42
+#define GPIO43_SPI                43
+#define GPIO44_SPI                44
+#define GPIO45_SPI                45
+#define GPIO46_I2C_SCL0           46
+#define GPIO47_I2C_SDA0           47
+#define GPIO48_I2C_SCL1           48
+#define GPIO49_I2C_SDA1           49
+#define GPIO50_I2C_SCL2_UART1_TX  50
+#define GPIO51_I2C_SDA2_UART1_RX  51
+#define GPIO52_ACL_BIT0_EN        52
+#define GPIO53_ACL_BIT1_EN        53
+#define GPIO54_ACL_BIT2_EN        54
+#define GPIO55_PTP_CLK_IN         55
+#define GPIO56_PTP_CLK_OUT        56
+#define GPIO57_PTP_TOD_OUT        57
+#define GPIO58_PTP_PPS_OUT        58
+#define GPIO59_PTP_TOD_IN         59
+#define GPIO60_PTP_PPS_IN         60
+#define GPIO61_SYNCELOCK0         61
+#define GPIO62_SYNCELOCK1         62
+#define GPIO63_MDIO               63
+
+/* Not available GPIO */
+#define GPIO_NA                   0xFF
+
+/* Convert SDA PIN GPIO to I2C bus number */
+uint8_t i2c_bus_from_sda_pin(uint8_t sda_pin);
+
+/* Convert SCL PIN GPIO to I2C bus number */
+uint8_t i2c_bus_from_scl_pin(uint8_t scl_pin);
+
+/*
+ * Setup a GPIO pin as input
+ * pin: GPIO pin number 0-63
+ */
+void gpio_input_setup(uint8_t pin);
+
+/*
+ * Setup a GPIO pin as output
+ * pin: GPIO pin number 0-63
+ * initial_val: 1 for bit set in RTL837X_REG_GPIO_xx_OUTPUT, 0 for bit not set
+ */
+void gpio_output_setup(uint8_t pin, __xdata uint8_t initial_val);
+
+#endif

rtl837x_port.c

@@ -356,20 +356,10 @@ void port_stats_print(void) __banked
 			else
 				print_string("Off\t");
 		} else {  // An SFP Module
-			if (i != 3) {
+			if (!gpio_pin_test(machine.sfp_port[machine.is_sfp[i]-1].pin_detect)) {
-				reg_read_m(RTL837X_REG_GPIO_00_31_INPUT);
+				print_string("SFP IN\t");
-				if (!(sfr_data[0] & 0x40)) {
-					print_string("SFP OK\t");
-				} else {
-					print_string("NO SFP\t");
-				}
 			} else {
-				reg_read_m(RTL837X_REG_GPIO_32_63_INPUT);
+				print_string("NO SFP\t");
-				if (!(sfr_data[1] & 0x04)) {
-					print_string("SFP OK\t");
-				} else {
-					print_string("NO SFP\t");
-				}
 			}
 		}
 

rtlplayground.c

@@ -8,6 +8,7 @@
 #include "rtl837x_regs.h"
 #include "rtl837x_common.h"
 #include "rtl837x_flash.h"
+#include "rtl837x_pins.h"
 #include "rtl837x_phy.h"
 #include "rtl837x_port.h"
 #include "rtl837x_stp.h"
@@ -807,7 +808,7 @@ uint8_t sfp_read_reg(uint8_t slot, uint8_t reg)
 	}
 
 	reg_read_m(RTL837X_REG_I2C_CTRL);
-	sfr_mask_data(1, 0xfc, machine.sfp_port[slot].i2c == 0 ? SCL_PIN << 5 | SDA_PIN_0 << 2 : SCL_PIN << 5 | SDA_PIN_1 << 2 );
+	sfr_mask_data(1, 0xfc, i2c_bus_from_scl_pin(machine.sfp_port[slot].i2c.scl) << 5 | i2c_bus_from_sda_pin(machine.sfp_port[slot].i2c.sda) << 2);
 	reg_write_m(RTL837X_REG_I2C_CTRL);
 
 	REG_WRITE(RTL837X_REG_I2C_IN, 0, 0, 0, reg);
@@ -1009,6 +1010,15 @@ bool gpio_pin_test(uint8_t pin)
 	return sfr_data[3-((pin >> 3) & 3)] & (1 << (pin & 7));
 }
 
+/* Inititalize SFP GPIOs */
+void setup_sfp_gpio(void)
+{
+	for (uint8_t sfp = 0; sfp < machine.n_sfp; sfp++) {
+		gpio_input_setup(machine.sfp_port[sfp].pin_detect);
+		gpio_input_setup(machine.sfp_port[sfp].pin_los);
+		gpio_output_setup(machine.sfp_port[sfp].pin_tx_disable, 0);
+	}
+}
 
 void handle_sfp(void)
 {
@@ -1538,7 +1548,6 @@ void led_config(void)
 	reg_write_m(RTL837X_REG_LED3_0_SET1);
 }
 
-
 void rtl8373_revision(void)
 {
 	reg_read_m(RTL837X_REG_CHIP_INFO);
@@ -1811,10 +1820,60 @@ void setup_i2c(void)
 
 	REG_SET(RTL837X_REG_I2C_CTRL2, 0);
 
-	// HW Control register, enable I2C?
+	// HW Control register, enable I2C depending on PIN configuration
 	reg_read_m(RTL837X_PIN_MUX_1);
-	sfr_mask_data(3, 0x20, 0x00); // Clear bit 29
+	for (uint8_t sfp = 0; sfp < machine.n_sfp; sfp++) {
-	sfr_mask_data(0, 0x60, 0x40); // Set bits 5-6 to 0b10
+		const uint8_t scl_bus = i2c_bus_from_scl_pin(machine.sfp_port[sfp].i2c.scl);
+		const uint8_t sda_bus = i2c_bus_from_sda_pin(machine.sfp_port[sfp].i2c.sda);
+		print_string("Configuring I2C for SFP idx="); print_byte(sfp); print_string(" SCL="); print_byte(scl_bus); print_string(", SDA="); print_byte(sda_bus); write_char('\n');
+		switch (scl_bus) {
+			case 3:
+				// Bit 5-6 0b10 -> SCL (implies enabled SDA on bus 3)
+				sfr_mask_data(0, 0x60, 0x40);
+				break;
+			case 2: 
+				// Bit 15-16 0b01 -> SCL
+				sfr_mask_data(1, 0x80, 0x80);
+				sfr_mask_data(2, 0x01, 0x00);
+				break;
+			case 1:
+				// Bit 11-12 0b01 -> SCL
+				sfr_mask_data(1, 0x18, 0x08);
+				break;
+			case 0:
+				// Bit 7-8 0b01 -> SCL
+				sfr_mask_data(0, 0x80, 0x80);
+				sfr_mask_data(1, 0x01, 0x00);
+				break;
+			default:
+				print_string("Invalid SCL bus number: "); print_byte(scl_bus); write_char('\n');
+		}
+
+		switch (sda_bus) {
+			case 4:
+				// Bit 29 0b0 -> SDA
+				sfr_mask_data(3, 0x20, 0x00);
+				break;
+			case 3:
+				// Bit 5-6 0b10 -> SDA (implies enabled SCL on bus 3)
+				sfr_mask_data(0, 0x60, 0x40);
+				break;
+			case 2:
+				// Bit 17-18 0b01 -> SDA
+				sfr_mask_data(2, 0x06, 0x02);
+				break;
+			case 1:
+				// Bit 13-14 0b01 -> SDA
+				sfr_mask_data(1, 0x60, 0x20);
+				break;
+			case 0:
+				// Bit 9-10 0b01 -> SDA
+				sfr_mask_data(1, 0x06, 0x02);
+				break;
+			default:
+				print_string("Invalid SDA bus number: "); print_byte(sda_bus); write_char('\n');
+		}
+	}
 	reg_write_m(RTL837X_PIN_MUX_1);	
 }
 

uip/uip_arp.c

@@ -142,7 +142,7 @@ static __xdata u8_t tmpage;
 void
 uip_arp_init(void) __banked
 {
-  print_string("uip_arp_init called");
+  print_string("uip_arp_init called\n");
   for(uint8_t i = 0; i < UIP_ARPTAB_SIZE; ++i) {
     memset(arp_table[i].ipaddr, 0, 4);
   }