Proposed I2C driver and MOS API implementation

MOS.wsp

@@ -4,3 +4,5 @@ ptn_Child1=Frames
 [WorkState_v1_2.Frames]
 ptn_Child1=ChildFrames
 
+[WorkState_v1_2.Frames.ChildFrames]
+

MOS.zdsproj

@@ -30,6 +30,7 @@
 <file filter-key="">src\config.h</file>
 <file filter-key="">src\mos_api.inc</file>
 <file filter-key="">src\defines.h</file>
+<file filter-key="">src\i2c.c</file>
 </files>
 
 <!-- configuration information -->
@@ -284,4 +285,4 @@
 <breakpoints>
 </breakpoints>
 
-</project>
+</project>

main.c

@@ -42,6 +42,7 @@
 #include "ff.h"
 #include "clock.h"
 #include "mos.h"
+#include "i2c.h"
 
 #define		MOS_version		1
 #define		MOS_revision 	4
@@ -51,6 +52,7 @@ extern void *	set_vector(unsigned int vector, void(*handler)(void));
 
 extern void 	vblank_handler(void);
 extern void 	uart0_handler(void);
+extern void 	i2c_handler(void);
 
 extern char 			coldBoot;		// 1 = cold boot, 0 = warm boot
 extern volatile	char 	keycode;		// Keycode 
@@ -98,6 +100,7 @@ int wait_ESP32(UART * pUART, UINT24 baudRate) {
 void init_interrupts(void) {
 	set_vector(PORTB1_IVECT, vblank_handler); 	// 0x32
 	set_vector(UART0_IVECT, uart0_handler);		// 0x18
+	set_vector(I2C_IVECT, i2c_handler);			// 0x1C
 }
 
 // The main loop

src/i2c.c

@@ -0,0 +1,155 @@
+/*
+ * Title:			AGON MOS - I2C code
+ * Author:			Jeroen Venema
+ * Created:			07/11/2023
+ * Last Updated:	10/11/2023
+ * 
+ * Modinfo:
+ */
+
+#include <ez80.h>
+#include "i2c.h"
+#include <defines.h>
+#include "timer.h"
+
+// Set I2C clock and sampling frequency
+void I2C_setfrequency(UINT8 id) {
+	switch(id) {
+		case(I2C_SPEED_115200):
+			I2C_CCR = (0x01<<3) | 0x03;	// 115.2KHz fast-mode (400KHz max), sampling at 4.6MHz
+			break;
+		case(I2C_SPEED_230400):
+			I2C_CCR = (0x01<<3) | 0x02;	// 230.4KHz fast-mode (400KHz max), sampling at 2.3Mhz
+			break;
+		case(I2C_SPEED_57600):
+		default:
+			I2C_CCR = (0x01<<3) | 0x04;	// 57.6KHz default standard-mode (100KHz max), sampling at 1.15Mhz
+	}
+}
+
+// Initializes the I2C bus
+void init_I2C(void) {
+	i2c_msg_size = 0;
+	CLK_PPD1 = CLK_PPD_I2C_OFF;			// Power Down I2C block before enabling it, avoid locking bug
+	I2C_CTL = I2C_CTL_ENAB;				// Enable I2C block, don't enable interrupts yet
+	I2C_setfrequency(0);
+	CLK_PPD1 = 0x0;						// Power up I2C block
+}
+
+// Internal function
+void I2C_handletimeout(void) {
+	// reset the interface
+	I2C_CTL = 0;
+	init_I2C();
+}
+
+// Open the I2C bus, register the driver interrupt
+// Parameters: None
+// Returns: None
+void mos_I2C_OPEN(UINT8 frequency) {
+	init_I2C();
+	I2C_setfrequency(frequency);
+}
+
+// Close the I2C bus, deregister the driver interrupt
+// Parameters: None
+// Returns: None
+void mos_I2C_CLOSE(void) {
+	CLK_PPD1 = CLK_PPD_I2C_OFF;			// Power Down I2C block
+	I2C_CTL &= ~(I2C_CTL_ENAB);			// Disable I2C block
+}
+
+// Write a number of bytes to an address on the I2C bus
+// Parameters:
+// - i2c_address: I2C address of the slave device
+// - size: number of bytes to write
+// - buffer: pointer to the first byte to write
+// Returns:
+// - 0 on success, or errorcode
+UINT8 mos_I2C_WRITE(UINT8 i2c_address, UINT8 size, char * buffer) {
+
+	// send maximum of 32 bytes in a single I2C transaction
+	if(size > I2C_MAX_BUFFERLENGTH) size = I2C_MAX_BUFFERLENGTH;
+	if(i2c_address > 127) return RET_NORESPONSE;
+	// wait for IDLE status
+	init_timer0(1, 16, 0x00);  		// 1ms timer for delay
+	enable_timer0(1);
+	while(i2c_role) {
+		// anything but IDLE (00)
+		if(get_timer0() > I2C_TIMEOUTMS) {
+			I2C_handletimeout();
+			enable_timer0(0);		// Disable timer
+			return RET_ARB_LOST;
+		}
+	}
+	enable_timer0(0);
+
+	i2c_msg_ptr = buffer;
+	i2c_msg_size = size;
+	i2c_role = I2C_MTX;			// MTX - Master Transmit Mode
+	i2c_error = RET_OK;
+	i2c_slave_rw = i2c_address << 1;	// shift one bit left, 0 on bit 0 == write action on I2C
+
+	I2C_CTL = I2C_CTL_IEN | I2C_CTL_ENAB | I2C_CTL_STA; // send start condition
+
+	init_timer0(1, 16, 0x00);  		// 1ms timer for delay
+	enable_timer0(1);
+	while(i2c_role == I2C_MTX) {	// while MTX
+		if(get_timer0() > I2C_TIMEOUTMS) {
+			I2C_handletimeout();
+			enable_timer0(0);		// Disable timer
+			return RET_DATA_NACK;
+		}
+	}
+
+	enable_timer0(0);				// Disable timer
+	return i2c_error;
+}
+
+// Read a number of bytes from an i2c_address on the I2C bus
+// Parameters:
+// - i2c_address: I2C address of the slave device
+// - size: number of bytes to read
+// - buffer: pointer to the first byte to read
+// Returns:
+// - 0 on success, or errorcode
+UINT8 mos_I2C_READ(UINT8 i2c_address, UINT8 size, char* buffer)
+{
+	if(size == 0) return 0;
+	if(i2c_address > 127) return RET_NORESPONSE;
+	// receive maximum of 32 bytes in a single I2C transaction
+	if(size > I2C_MAX_BUFFERLENGTH) size = I2C_MAX_BUFFERLENGTH;
+
+	// wait for IDLE status
+	init_timer0(1, 16, 0x00);  		// 1ms timer for delay
+	enable_timer0(1);
+	while(i2c_role) {
+		// anything but IDLE (00)
+		if(get_timer0() > I2C_TIMEOUTMS) {
+			I2C_handletimeout();
+			enable_timer0(0);		// Disable timer
+			return RET_ARB_LOST;
+		}
+	}
+	enable_timer0(0);
+	i2c_msg_ptr = buffer;
+	i2c_msg_size = size;
+	i2c_role = I2C_MRX;			// MRX mode
+	i2c_error = RET_OK;
+	i2c_slave_rw = (1<<0);				// receive bit 0
+	i2c_slave_rw |= i2c_address << 1;	// shift 7-bit address one bit left
+
+	I2C_CTL = I2C_CTL_IEN | I2C_CTL_ENAB | I2C_CTL_STA; // send start condition
+
+	init_timer0(1, 16, 0x00);  		// 1ms timer for delay
+	enable_timer0(1);
+	while(i2c_role == I2C_MRX) {
+		if(get_timer0() > I2C_TIMEOUTMS) {
+			I2C_handletimeout();
+			enable_timer0(0);		// Disable timer
+			return RET_ARB_LOST;
+		}
+	}
+	enable_timer0(0);				// Disable timer
+	return i2c_error;
+}

src/i2c.h

@@ -0,0 +1,51 @@
+#ifndef _I2C_H_
+#define _I2C_H_
+
+#include <defines.h>
+
+
+extern volatile char	i2c_slave_rw;
+extern volatile char	i2c_error;
+extern volatile char	i2c_role;
+extern volatile UINT8	i2c_msg_size;
+extern volatile char *	i2c_msg_ptr;
+
+// I2C_CTL register bits
+#define I2C_CTL_IEN		(1<<7)
+#define I2C_CTL_ENAB	(1<<6)
+#define I2C_CTL_STA		(1<<5)
+#define I2C_CTL_STP		(1<<4)
+#define I2C_CTL_IFLG	(1<<3)
+#define I2C_CTL_AAK		(1<<2)
+
+// ez80 PPD register bits
+#define CLK_PPD_I2C_OFF	(1<<2)
+
+// I2C return codes to caller
+#define RET_OK			0x00
+#define RET_NORESPONSE	0x01
+#define RET_DATA_NACK	0x02
+#define RET_ARB_LOST	0x04
+#define RET_BUS_ERROR	0x08
+
+// I2C constants
+#define I2C_MAX_BUFFERLENGTH	32
+#define I2C_TIMEOUTMS			2000
+#define I2C_SPEED_57600			0x01
+#define I2C_SPEED_115200		0x02
+#define I2C_SPEED_230400		0x03
+
+// I2C role state
+#define I2C_IDLE				0x00
+#define I2C_MTX					0x01
+#define I2C_MRX					0x02
+#define I2C_SRX					0x04
+#define I2C_STX					0x08
+
+void init_I2C(void);
+void	mos_I2C_OPEN(UINT8 frequency);
+void	mos_I2C_CLOSE(void);
+UINT8	mos_I2C_WRITE(UINT8 i2c_address, UINT8 size, char * buffer);
+UINT8	mos_I2C_READ(UINT8 i2c_address, UINT8 size, char * buffer);
+
+#endif _I2C_H_

src/i2c.inc

@@ -0,0 +1,21 @@
+;* Return status codes to read/write caller
+RET_OK					.equ	00h	; ok - caller sets this at entry
+RET_NORESPONSE			.equ	01h	; address sent, nack received
+RET_DATA_NACK			.equ	02h ; data sent, nack received
+RET_ARB_LOST			.equ	04h ; arbitration lost
+RET_BUS_ERROR			.equ	08h ; Bus error
+
+;* I2C ROLE STATUS
+I2C_IDLE				.equ	00h
+I2C_MTX					.equ	01h
+I2C_MRX					.equ	02h
+I2C_SRX					.equ	04h
+I2C_STX					.equ	08h
+
+;* I2C_CTL bits
+I2C_CTL_IEN				.equ	10000000b
+I2C_CTL_ENAB			.equ	01000000b
+I2C_CTL_STA				.equ	00100000b
+I2C_CTL_STP				.equ	00010000b
+I2C_CTL_IFLG			.equ	00001000b
+I2C_CTL_AAK				.equ	00000100b