lcd - Stream HAL data to an LCD screen


loadrt lcd fmt_strings=""Plain Text %4.4f\nAnd So on|Second Page, Next Inst""


lcd (requires a floating-point thread).

All LCD instances are updated by the same function.


lcd.NN.out (u32) out

The output byte stream is sent via this pin. One character is sent every thread invocation. There in no handshaking provided. (float/s32/u32/bit) in

The input pins have types matched to the format string specifiers.

lcd.NN.page_num (u32) in

Selects the page number. Multiple layouts may be defined, and this pin switches between them.

lcd.NN.contrast (float) in

Attempts to set the contrast of the LCD screen using the byte sequence ESC C and then a value from 0x20 to 0xBF (matching the Mesa 7I73). The value should be between 0 and 1.


lcd.NN.decimal-separator (u32) rw

Sets the decimal separator used for floating point numbers. The default value is 46 (0x2E) which corresponds to ".". If a comma is required then set this parameter to 44 (0x2C).


lcd takes format strings much like those used in C and many other languages in the printf and scanf functions and their variants.

The component was written specifically to support the Mesa 7I73 pendant controller, however, it may be of use streaming data to other character devices and, as the output format mimics the ADM3 terminal format, it could be used to stream data to a serial device. Perhaps even a genuine ADM3. The strings contain a mixture of text values (which are displayed directly), "escaped" formatting codes and numerical format descriptors. For a detailed description of formatting codes see: .

The component can be configured to display an unlimited number of differently-formatted pages, which may be selected with a HAL pin.
Escaped codes

\n Inserts a clear-to-end, carriage return and line feed character. This will still linefeed and clear even if an automatic wrap has occurred (lcd has no knowledge of the width of the lcd display). To print in the rightmost column it is necessary to allow the format to wrap and omit the \n code.

\t Inserts a tab (actually 4 spaces in the current version rather than a true tab.)

\NN inserts the character defined by the hexadecimal code NN.
As the ’,’ character is used in the format string to separate LCD instances it must be represented by \2C in the format string (the decimal separator is handled differently).

\\ Inserts a literal \.

Numerical formats

lcd differs slightly from the standard printf conventions. One significant difference is that width limits are strictly enforced to prevent the LCD display wrapping and spoiling the layout. The field width includes the sign character so that negative numbers will often have a smaller valid range than positive. Numbers that do not fit in the specified width are displayed as a line of asterisks (********).

Each format begins with a "%" symbol. (For a literal % use "%%"). Immediately after the % the following modifiers may be used:

" " (space) Pad the number to the specified width with spaces. This is the default and is not strictly necessary.

"0" Pad the number to the specified width with the numeral 0.

"+" Force display of a + symbol before positive numbers. This (like the - sign) will appear immediately to the left of the digits for a space-padded number and in the extreme left position for a 0-padded number.

"1234567890" A numerical entry (other than the leading 0 above) defines the total number of characters to display including the decimal separator and the sign. Whilst this number can be as many digits as required, the maximum field width is 20 characters. The inherent precision of the "double" data type means that more than 14 digits will tend to show errors in the least significant digits. The integer data types will never fill more than 10 decimal digits.

Following the width specifier should be the decimal specifier. This can only be a full-stop character (.) as the comma (,) is used as the instance separator. Currently lcd does not access the locale information to determine the correct separator but the decimal-separator HAL parameter can be used to choose any desired separator.

Following the decimal separator should be a number that determines how many places of decimals to display. This entry is ignored in the case of integer formats.

All the above modifiers are optional, but to specify a decimal precision the decimal point must precede the precision, e.g., as in "%.3f". The default decimal precision is 4.

The numerical formats supported are:

%f %F (for example, %+09.3f) These create a floating-point type HAL pin. The example would be displayed in a 9-character field, with 3 places of decimals, as a decimal separator, padded to the left with 0s and with a sign displayed for both positive and negative. Conversely a plain %f would be 6 digits of decimal, variable format width, with a sign only shown for negative numbers. Both %f and %F create exactly the same format.

%i %d (For example %+ 4d) Creates a signed (s32) HAL pin. The example would display the value at a fixed 4 characters, space padded, width including the "+" giving a range of +999 to -999. %i and %d create identical output.

%u (for example %08u) Creates an unsigned (u32) HAL pin. The example would be a fixed 8 characters wide, padded with zeros.

%x, %X Creates an unsigned (u32) HAL pin and displays the value in Hexadecimal. Both %x and %X display capital letters for digits ABCDEF. A width may be specified, though the u32 HAL type is only 8 hex digits wide.

%o Creates an unsigned (u32) pin and displays the value in octal representation.

%c Creates a u32 HAL pin and displays the character corresponding to the value of the pin. Values less than 32 (space) are suppressed. A width specifier may be used, for example %20c might be used to create a complete line of one character.

%b This specifier has no equivalent in printf. It creates a bit (boolean) type HAL pin. The b should be followed by two characters and the display will show the first of these when the pin is true, and the second when false. Note that the characters follow, not precede the "b", unlike the case with other formats. The characters may be "escaped" Hex values. For example "%b\FF " will display a solid black block if true, and a space if false and "%b\7F\7E" would display right-arrow for false and left-arrow for true. An unexpected value of ’E’ indicates a formatting error.

Pages The page separator is the "|" (pipe) character (if the actual character is needed then \7C may be used). A "Page" in this context refers to a separate format which may be displayed on the same display.

Instances The instance separator is the comma. This creates a completely separate lcd instance, for example to drive a second lcd display on the second 7I73. The use of comma to separate instances is built in to the modparam reading code so not even escaped commas "\," can be used. A comma may be displayed by using the \2C sequence.


Andy Pugh