WIP write multiple registers

fw/Core/Inc/modbus.h

@@ -107,6 +107,7 @@ typedef enum {
 typedef enum {
 	MODBUS_EXCEPTION_ILLEGAL_FUNCTION = 1,
 	MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS = 2,
+	MODBUS_EXCEPTION_ILLEGAL_REGISTER_QUANTITY = 2,
 	MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE = 3,
 	MODBUS_EXCEPTION_SLAVE_DEVICE_FAILURE = 4,
 	MODBUS_EXCEPTION_ACKNOWLEDGE = 5,

fw/Core/Src/main.c

@@ -291,6 +291,10 @@ int main(void)
 		  /* TODO: Process data and light a desired color of LED */
 		  /* TODO: Add hystheresis */
 
+		  /* Reset the TIM21 Elapsed Period Flag */
+		  tim21_elapsed_period = 0;
+	  }
+	  /* TEST END */
 	  if (sensor_config.led_on) {
 			  if (CO2 <= sensor_config.led_co2_alert_limit1) {
 				  /* CO2 is OK -> GREEN */
@@ -315,11 +319,6 @@ int main(void)
 			  LL_GPIO_SetOutputPin(LED_G_GPIO_Port, LED_G_Pin);
 			  LL_GPIO_SetOutputPin(LED_B_GPIO_Port, LED_B_Pin);
 		  }
-
-		  /* Reset the TIM21 Elapsed Period Flag */
-		  tim21_elapsed_period = 0;
-	  }
-	  /* TEST END */
     /* USER CODE END WHILE */
 
     /* USER CODE BEGIN 3 */

fw/Core/Src/modbus.c

@@ -58,6 +58,7 @@ int8_t modbus_copy_reply_to_buffer(uint8_t *buffer, uint8_t *msg_len, modbus_tra
 	uint16_t crc16;
 	uint8_t byte_count;
 
+	// TODO use relative indices (increments) instead of absolute
 	buffer[0] = modbus_slave_address;
 	buffer[1] = transaction->function_code;
 	*msg_len = 5;
@@ -86,6 +87,13 @@ int8_t modbus_copy_reply_to_buffer(uint8_t *buffer, uint8_t *msg_len, modbus_tra
 				buffer[5] = (uint8_t) transaction->holding_registers[0];
 				*msg_len = 8;
 				break;
+			case MODBUS_WRITE_MULTIPLE_REGISTERS:
+				buffer[2] = (uint8_t) (transaction->register_address >> 8);
+				buffer[3] = (uint8_t) transaction->register_address;
+				buffer[4] = (uint8_t) (transaction->register_count >> 8);
+				buffer[5] = (uint8_t) transaction->register_count;
+				*msg_len = 8;
+
 		}
 	}
 	crc16 = modbus_CRC16(buffer, *msg_len - 2); /* last two bytes is the checksum itself */
@@ -109,11 +117,18 @@ int8_t modbus_slave_set_address(uint8_t address)
 
 int8_t modbus_slave_process_msg(const uint8_t *buffer, int len)
 {
+	/*
+	 * TODO list:
+	 *
+	 * 1) check that errors and exceptions are handled according to Modbus_Application_Protocol_V1_1b.pdf
+	 * 2) buffer overflow prevention: for each function code, check that buffer is long enough
+	 */
 	/* transaction holds message context and content:
 	 * it wraps all necessary buffers and variables */
 	modbus_transaction_t transaction;
 	int8_t callback_result;
 	uint8_t buffer_pos = 0;
+	uint8_t byte_count;
 
 	if (len < MODBUS_MINIMAL_FRAME_LEN) {
 		/* frame too short; return error */
@@ -188,11 +203,22 @@ int8_t modbus_slave_process_msg(const uint8_t *buffer, int len)
 			return MODBUS_ERROR;
 		}
 		transaction.register_address = (buffer[buffer_pos++] << 8) | buffer[buffer_pos++];
+		// TODO check length!
 		if (flags & MODBUS_FLAG_WRITE) {
 			if (flags & MODBUS_FLAG_SINGLE) {
 				transaction.holding_registers[0] = (buffer[buffer_pos++] << 8) | buffer[buffer_pos++];
 			} else {
-				// write multiple register - TODO
+				/* Write multiple registers */
+				transaction.register_count = (buffer[buffer_pos++] << 8) | buffer[buffer_pos++];
+				byte_count = buffer[buffer_pos++];
+				if (transaction.register_count > 123 || 2*transaction.register_count != byte_count) {
+					/* Max number of register is defined by Modbus_Application_Protocol_V1_1b, section 6.12 */
+					transaction.exception.exception_code = MODBUS_EXCEPTION_ILLEGAL_REGISTER_QUANTITY;
+				} else {
+					for (uint8_t i = 0; i < transaction.register_count; i++) {
+						transaction.holding_registers[i] = (buffer[buffer_pos++] << 8) | buffer[buffer_pos++];
+					}
+				}
 			}
 		} else {
 			transaction.register_count = (buffer[buffer_pos++] << 8) | buffer[buffer_pos++];

tests/write_multiple_holding_registers_test.py

@@ -0,0 +1,41 @@
+#!/usr/bin/env python3
+from time import sleep
+from sys import exit
+import minimalmodbus
+import serial
+
+slave_address = 254
+instrument = minimalmodbus.Instrument('/dev/ttyUSB0', slave_address, close_port_after_each_call=True)  # port name, slave address (in decimal)
+
+instrument.serial.baudrate = 19200
+instrument.serial.bytesize = 8
+instrument.serial.parity   = serial.PARITY_EVEN
+instrument.serial.stopbits = 1
+instrument.serial.timeout  = 0.05          # seconds
+instrument.mode = minimalmodbus.MODE_RTU   # rtu or ascii mode
+instrument.clear_buffers_before_each_transaction = True
+
+# holding register numbers
+LED_on_register = 0
+LED_brightness_register = 1
+LED_smooth_register = 2
+CO2_alert_limit_1_register = 3
+CO2_alert_limit_2_register = 4
+SCD4x_temperature_offset_register = 5
+MODBUS_address_register = 6
+baudrate_register = 7
+# values
+LED_on = 1
+LED_brightness = 100
+LED_smooth = 0
+CO2_alert_limit_1 = 1000
+CO2_alert_limit_2 = 2000
+SCD4x_temperature_offset = 0
+MODBUS_address = 254
+baudrate = 0
+registers = [LED_on, LED_brightness, LED_smooth, CO2_alert_limit_1, CO2_alert_limit_2, SCD4x_temperature_offset, MODBUS_address, baudrate]
+# write to holding registers
+print('---- Writing to multiple holding registers ----')
+instrument.write_registers(LED_on_register, registers)
+print('---- DONE ----')
+exit(0)