"""Program 4-7: Example of querying the user for an input
           Connect the GP21 pin and the GP20 pin to a PC through
           a USB-to-Serial Converter
"""

from machine import UART, Pin

uart1 = UART(1, baudrate = 9600, rx = Pin(21), tx = Pin(20))

def uart1_get_char():
    """This is a blocking function to get a character from UART1"""
    while True:
        char = uart1.read(1)
        if char is not None:
            print(char)   # for debugging only
            return char

def uart1_get_line():
    """Read a line ending with a carriage return character ('\r')"""
    s = bytearray()                    # instatiate an empty byte array

    while True:
        c = uart1_get_char()           # get a character from UART1

        if c == b'\r':                 # if enter key was hit
            print('eol')               # for debugging only
            return s                   # return the bytearray

        if c == b'\b':                 # for backspace
            if len(s) > 0:             # do nothing if the bytearray is empty
                s = s[:-1]             # otherwise, trim the last character entered
                uart1.write(b'\b \b')  # echo backspace-space-backspace
        else:
            uart1.write(c)             # echo the character
            print(s, c)                # for debugging only
            s = s + c                  # append the new character to the end of s

def uart1_get_number():
    """Read a string from UART1 and convert it to a float number"""
    s = uart1_get_line()
    print(s, type(s))          # for debugging only
    f = float(s)               # convert bytearray to a floating-point number
    print(f, type(f))          # for debugging only
    return f


uart1.write('\r\nPlease enter a number: ') # give user a prompt
n = uart1_get_number()                     # get a number from user input
print(n, type(n))                          # for debugging only
sn = str(n)                                # convert to a string for UART write
print(sn, type(sn))                        # for debugging only
uart1.write('\r\nYou have entered a number ' + sn + '\r\n')