CAN echo systest

4 files changed, 150 insertions, 27 deletions

diff --git a/fw/can.c b/fw/can.c
index 6518f91..b3f41f9 100644
--- a/fw/can.c
+++ b/fw/can.c
@@ -113,7 +113,7 @@ enum {
 	// TXBnDLC
 	RTR = 0x40,
 
-	EXIDE = 0x08, // extended identifier enable bit in SIDL registers
+	IDE = 0x08, // extended identifier flag bit of SIDL registers
 };
 
 // Instructions
@@ -236,29 +236,65 @@ canIE(bool enable) {
 	}
 }
 
+// Pack ID register values into a struct.
 static void
-readRxbnData(U8 n, U8 data[8u]) {
+packId(CanId *id, U8 sidh, U8 sidl, U8 eid8, U8 eid0) {
+	if (sidl & IDE) { // extended ID
+		id->type = CAN_ID_EXT;
+		id->eid[0] = (U8)(sidh << 3u) | (U8)(sidl >> 5u); // sid[7:0]
+		id->eid[1] = (U8)(eid0 << 3u) | (U8)(sidh >> 5u); //eid[4:0], sid[10:8]
+		id->eid[2] = (U8)(eid8 << 3u) | (U8)(eid0 >> 5u); // eid[12:5]
+		id->eid[3] = (U8)((sidl & 0x3) << 3u) | (U8)(eid8 >> 5u); // eid[17:13]
+	} else { // standard ID
+		id->type = CAN_ID_STD;
+		id->sid.lo = (U8)(sidh << 3u) | (U8)(sidl >> 5u); // sid[7:0]
+		id->sid.hi = sidh >> 5u; // sid[10:8]
+	}
+}
+
+static void
+readRxbn(U8 n, CanFrame *frame) {
+	U8 sidh, sidl, eid8, eid0;
+
 	CAN_CS = 0;
-	n &= 0x01; // n in {0,1}
-	(void)spiTx(CMD_READ_RX | (U8)(n << 2u) | 0x02); // start at RXBnD0
-	for (n = 0u; n < 8u; n++) {
-		data[n] = spiTx(0x00);
+
+	// Start reading at RXBnSIDH
+	(void)spiTx(CMD_READ_RX | (U8)((n & 1u) << 2u));
+
+	// Read ID
+	sidh = spiTx(0u);
+	sidl = spiTx(0u);
+	eid8 = spiTx(0u);
+	eid0 = spiTx(0u);
+	packId(&frame->id, sidh, sidl, eid8, eid0);
+
+	// Read RTR and DLC
+	frame->dlc = spiTx(0u);
+	frame->rtr = frame->dlc & RTR;
+	frame->dlc &= 0xF;
+
+	// Read data
+	for (n = 0u; n < frame->dlc; n++) {
+		frame->data[n] = spiTx(0u);
 	}
+
 	CAN_CS = 1;
 }
 
 void
-canReadRxb0Data(U8 data[8u]) {
-	readRxbnData(0u, data);
+canReadRxb0(CanFrame *frame) {
+	readRxbn(0u, frame);
 }
 
 void
-canReadRxb1Data(U8 data[8u]) {
-	readRxbnData(1u, data);
+canReadRxb1(CanFrame *frame) {
+	readRxbn(1u, frame);
 }
 
+// Write an ID to a set of {xSIDH, xSIDL, xEID8, xEID0} registers,
+// e.g., RXMnSIDH etc.
 static void
-writeIdToRegs(const CanId *id, Reg sidh, Reg sidl, Reg eid8, Reg eid0) {
+writeId(const CanId *id, Reg sidh, Reg sidl, Reg eid8, Reg eid0) {
 	switch (id->type) {
 	case CAN_ID_STD: // standard ID
 		write(sidh, (U8)(id->sid.hi << 5u) | (U8)(id->sid.lo >> 3u));
@@ -268,7 +304,7 @@ writeIdToRegs(const CanId *id, Reg sidh, Reg sidl, Reg eid8, Reg eid0) {
 		break;
 	case CAN_ID_EXT: // extended ID
 		write(sidh, (U8)(id->eid[1] << 5u) | (U8)(id->eid[0] >> 3u)); // sid[10:3]
-		write(sidl, (U8)(id->eid[0] << 5u) | EXIDE | (U8)((id->eid[3] >> 3u) & 0x03)); // sid[2:0], exide, eid[28:27]
+		write(sidl, (U8)(id->eid[0] << 5u) | IDE | (U8)((id->eid[3] >> 3u) & 0x03)); // sid[2:0], exide, eid[28:27]
 		write(eid8, (U8)(id->eid[3] << 5u) | (U8)(id->eid[2] >> 3u)); // eid[26:19]
 		write(eid0, (U8)(id->eid[2] << 5u) | (U8)(id->eid[1] >> 3u)); // eid[18:11]
 		break;
@@ -280,7 +316,7 @@ canTx(const CanFrame *frame) {
 	U8 k, ctrl;
 
 	// Set ID, DLC, and RTR
-	writeIdToRegs(&frame->id, REG_TXB0SIDH, REG_TXB0SIDL, REG_TXB0EID8, REG_TXB0EID0);
+	writeId(&frame->id, REG_TXB0SIDH, REG_TXB0SIDL, REG_TXB0EID8, REG_TXB0EID0);
 	write(REG_TXB0DLC, (frame->dlc & 0x0F) | ((frame->rtr) ? RTR : 0));
 
 	// Copy data to registers
@@ -305,40 +341,40 @@ canTx(const CanFrame *frame) {
 
 void
 canSetMask0(const CanId *mask) {
-	writeIdToRegs(mask, REG_RXM0SIDH, REG_RXM0SIDL, REG_RXM0EID8, REG_RXM0EID0);
+	writeId(mask, REG_RXM0SIDH, REG_RXM0SIDL, REG_RXM0EID8, REG_RXM0EID0);
 }
 
 void
 canSetMask1(const CanId *mask) {
-	writeIdToRegs(mask, REG_RXM1SIDH, REG_RXM1SIDL, REG_RXM1EID8, REG_RXM1EID0);
+	writeId(mask, REG_RXM1SIDH, REG_RXM1SIDL, REG_RXM1EID8, REG_RXM1EID0);
 }
 
 void
 canSetFilter0(const CanId *filter) {
-	writeIdToRegs(filter, REG_RXF0SIDH, REG_RXF0SIDL, REG_RXF0EID8, REG_RXF0EID0);
+	writeId(filter, REG_RXF0SIDH, REG_RXF0SIDL, REG_RXF0EID8, REG_RXF0EID0);
 }
 
 void
 canSetFilter1(const CanId *filter) {
-	writeIdToRegs(filter, REG_RXF1SIDH, REG_RXF1SIDL, REG_RXF1EID8, REG_RXF1EID0);
+	writeId(filter, REG_RXF1SIDH, REG_RXF1SIDL, REG_RXF1EID8, REG_RXF1EID0);
 }
 
 void
 canSetFilter2(const CanId *filter) {
-	writeIdToRegs(filter, REG_RXF2SIDH, REG_RXF2SIDL, REG_RXF2EID8, REG_RXF2EID0);
+	writeId(filter, REG_RXF2SIDH, REG_RXF2SIDL, REG_RXF2EID8, REG_RXF2EID0);
 }
 
 void
 canSetFilter3(const CanId *filter) {
-	writeIdToRegs(filter, REG_RXF3SIDH, REG_RXF3SIDL, REG_RXF3EID8, REG_RXF3EID0);
+	writeId(filter, REG_RXF3SIDH, REG_RXF3SIDL, REG_RXF3EID8, REG_RXF3EID0);
 }
 
 void
 canSetFilter4(const CanId *filter) {
-	writeIdToRegs(filter, REG_RXF4SIDH, REG_RXF4SIDL, REG_RXF4EID8, REG_RXF4EID0);
+	writeId(filter, REG_RXF4SIDH, REG_RXF4SIDL, REG_RXF4EID8, REG_RXF4EID0);
 }
 
 void
 canSetFilter5(const CanId *filter) {
-	writeIdToRegs(filter, REG_RXF5SIDH, REG_RXF5SIDL, REG_RXF5EID8, REG_RXF5EID0);
+	writeId(filter, REG_RXF5SIDH, REG_RXF5SIDL, REG_RXF5EID8, REG_RXF5EID0);
 }
diff --git a/fw/can.h b/fw/can.h
index 8e0cfff..9ac1cfe 100644
--- a/fw/can.h
+++ b/fw/can.h
@@ -52,9 +52,9 @@ typedef struct {
 // CAN frame
 typedef struct {
 	CanId id;
+	bool rtr; // remote transmission request
 	U8 dlc; // data length code
 	U8 data[8];
-	bool rtr; // remote transmission request
 } CanFrame;
 
 // Initialize the MCP2515.
@@ -75,11 +75,11 @@ void canIE(bool enable);
 // Read RX status with RX STATUS instruction.
 U8 canRxStatus(void);
 
-// Read the DATA field of RXB0.
-void canReadRxb0Data(U8 data[8u]);
+// Read the frame in RXB0.
+void canReadRxb0(CanFrame *frame);
 
-// Read the DATA field of RXB1.
-void canReadRxb1Data(U8 data[8u]);
+// Read the frame in RXB1.
+void canReadRxb1(CanFrame *frame);
 
 // Transmit a frame to the CAN bus
 Status canTx(const CanFrame *frame);
diff --git a/fw/tests/system/can_echo_systest.c b/fw/tests/system/can_echo_systest.c
new file mode 100644
index 0000000..798e45f
--- /dev/null
+++ b/fw/tests/system/can_echo_systest.c
@@ -0,0 +1,85 @@
+/* Listen for a standard DATA FRAME with ID 123h;
+ * echo it back with each byte of the DATA FIELD incremented by 1.
+ */
+
+#include <xc.h>
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include "system.h"
+#include "types.h"
+#include "spi.h"
+#include "can.h"
+
+void
+main(void) {
+	sysInit();
+	spiInit();
+	canInit();
+
+	// Setup MCP2515 CAN controller
+	canSetBitTiming(CAN_TIMING_10K);
+	CanId id = {
+		.type=CAN_ID_STD,
+		.sid = {0xFF, 0xFF},
+	};
+	canSetMask0(&id); // set masks
+	canSetMask1(&id);
+	canSetFilter1(&id); // set unused filters
+	canSetFilter2(&id);
+	canSetFilter3(&id);
+	canSetFilter4(&id);
+	canSetFilter5(&id);
+	id.sid = (U16){0x01, 0x23}; // listen for message on filter 0
+	canSetFilter0(&id);
+	canIE(true); // enable interrupts on INT pin
+	canSetMode(CAN_MODE_NORMAL);
+	
+	// Enable interrupts
+	INTCON = 0x00; // clear flags
+	OPTION_REGbits.INTEDG = 0; // interrupt on falling edge
+	INTCONbits.INTE = 1; // enable INT pin
+	INTCONbits.PEIE = 1; // enable peripheral interrupts
+	INTCONbits.GIE = 1; // enable global interrupts
+
+	for (;;) {
+
+	}
+}
+
+// Add 1 to each data byte of a CAN frame and transmit it to the bus.
+static void
+echo(CanFrame *frame) {
+	U8 k;
+
+	for (k = 0u; k < frame->dlc; k++) {
+		frame->data[k]++;
+	}
+
+	canTx(frame);
+}
+
+void
+__interrupt() isr(void) {
+	U8 status;
+	CanFrame frame;
+
+	if (INTCONbits.INTF) {
+		status = canRxStatus();
+		switch (status & 0x7) { // check filter match
+		case 0u: // RXF0
+			canReadRxb0(&frame);
+			echo(&frame);
+			break;
+		case 1u: // RXF1
+			canReadRxb0(&frame); // clear interrupt flag
+			break;
+		default:
+			// Message in RXB1
+			canReadRxb1(&frame); // clear interrupt flag
+		}
+
+		INTCONbits.INTF = 0;
+	}
+}
diff --git a/fw/tests/system/can_tx_systest.c b/fw/tests/system/can_tx_systest.c
index b1dec17..ef1d7b0 100644
--- a/fw/tests/system/can_tx_systest.c
+++ b/fw/tests/system/can_tx_systest.c
@@ -1,3 +1,5 @@
+/* Periodically transmit a frame to the CAN bus. */
+
 #include <xc.h>
 
 #include <stdbool.h>
@@ -14,9 +16,9 @@ static const CanFrame frame = {
 		.type = CAN_ID_STD,
 		.sid = {0x01, 0x23},
 	},
+	.rtr = false,
 	.dlc = 8u,
 	.data = {0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77},
-	.rtr = false,
 };
 
 static U8 ctr = 0u; // timer