Setting up USB -> Modbus (CH340) for VFD control

lsusb

bridgeport@bridgeport-H81M-S2PH ~ $ lsusb
Bus 002 Device 002: ID 8087:8000 Intel Corp. 
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 8087:8008 Intel Corp. 
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 003 Device 006: ID 148f:5370 Ralink Technology, Corp. RT5370 Wireless Adapter
Bus 003 Device 005: ID 222a:0045  
Bus 003 Device 004: ID 1a86:7523 QinHeng Electronics HL-340 USB-Serial adapter
Bus 003 Device 003: ID 10ce:eb70 Silicon Labs 
Bus 003 Device 002: ID 1c4f:0034 SiGma Micro 
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

Bus 003 Device 004: ID 1a86:7523 QinHeng Electronics HL-340 USB-Serial adapter

[MB2HAL_INIT]
INIT_DEBUG=0
.
HAL_MODULE_NAME=mb2hal
SLOWDOWN=0.0
TOTAL_TRANSACTIONS=3

# Set Run Status
[TRANSACTION_00]
LINK_TYPE=serial
SERIAL_PORT=/dev/ttyS0
SERIAL_BAUD=9600
SERIAL_BITS=8
SERIAL_PARITY=none
SERIAL_STOP=1
SERIAL_DELAY_MS=3
MB_SLAVE_ID=1

FIRST_ELEMENT=7680
NELEMENTS=1
MB_TX_CODE=fnct_16_write_multiple_registers 
HAL_TX_NAME=run
MAX_UPDATE_RATE=0.0
DEBUG=3

# Set Frequency
[TRANSACTION_01] 
MB_TX_CODE=fnct_16_write_multiple_registers 
FIRST_ELEMENT=7681
NELEMENTS=1 
HAL_TX_NAME=frequency 
MAX_UPDATE_RATE=0.0 
DEBUG=3

# VFD Status
[TRANSACTION_02] 
MB_TX_CODE=fnct_02_read_discrete_inputs
FIRST_ELEMENT=0 
NELEMENTS=16 
HAL_TX_NAME=is-running 
MAX_UPDATE_RATE=0.0 
DEBUG=3

 #REQUIRED: Modbus transaction function code (see www.modbus.org specifications).
 #    fnct_02_read_discrete_inputs     (02 = 0x02)
 #    fnct_03_read_holding_registers   (03 = 0x03)
 #    fnct_04_read_input_registers     (04 = 0x04)
 #    fnct_15_write_multiple_coils     (15 = 0x0F)
 #    fnct_16_write_multiple_registers (16 = 0x10)
 #fnct_02_read_discrete_inputs: creates boolean output HAL pins.
 #fnct_03_read_holding_registers: creates a floating point output HAL pins.
 #                           also creates a u32 output HAL pins.
 #fnct_04_read_input_registers: creates a floating point output HAL pins.
 #                         also creates a u32 output HAL pins.
 #fnct_15_write_multiple_coils: creates boolean input HAL pins.
 #fnct_16_write_multiple_registers: creates a floating point input HAL pins.
 #The pins are named based on component name, transaction number and order number.
 #Example: mb2hal.00.01 (transaction=00, second register=01 (00 is the first one))