Serial Terminal Firmware for RP2040 Boards
RPTerm will implement a serial terminal with the following features planed:
- VGA video output (30 lines of 80 characters, 256 colors)
- USB keyboard input
- Serial communication with UART on GPIO 12 & 13 (configurable baud rate)
- Support for VT-100 style commands
- Generates VT-100 style sequences for cursor keys
- Status Line
- Configuration screen
- SD Card interface, with send & receive files (TODO)
The following ASCII control codes are supported:
- BEL (0x07): sounds a beep in the buzzer
- BS (0x08): move cursor to the right (stops on the first column)
- HT (0x09): moves cursor to the next tab stop (9, 17, 25, 33, 41, 49, 57, 65, 73)
- LF (0A): moves cursor down a line, scrolls up screen if at last line
- CR (0x0D): moves cursor to the first column
- FF (0x0C): clears screen and moves cursor to home (fist column of first row)
- ESC (0x1B): start of a control sequence
The following ANSI sequences are supported:
- ESC[{n}A | Move the cursor up {n} lines
- ESC[{n}B | Move the cursor down {n} lines
- ESC[{n}C | Move the cursor forward {n} characters
- ESC[{n}D | Move the cursor backward {n} characters
- ESC[H | Move to home
- ESC[{Row};{Col}H | Move to {Col} column at {Row} row
- ESC[0K | Clear from cursor to the end of the line
- ESC[1K | Clear from the beginning of the current line to the cursor
- ESC[2K | Clear the whole line
- ESC[0J | clear screen from cursor
- ESC[1J | clear screen to cursor
- ESC[2J | Clear the screen and move the cursor to home
- ESC[3J | same as \ESC[2J
- ESC[{n}S | scroll screen up by {n} rows
- ESC[?25h | Cursor visible
- ESC[?25l | Cursor invisible
- ESC[0m | normal text (set foreground & background colors to normal)
- ESC[7m | reverse text (exchange foreground & background colors}
- ESC[{fcolor}m | Set foreground color 30=black, 31=red, 32=green, 33=yellow, 34=blue, 35=magenta, 36=cyan, 37=white)
- ESC[38;5;{color}m | Set foreground color to {color} (0 to 255)
- ESC[{bcolor}m | Set background color 40=black, 41=red, 42=green, 43=yellow, 44=blue, 45=magenta, 46=cyan, 47=white)
- ESC[48;5;{color}m | Set background color to {color} (0 to 255)
- ESC[s | Save the cursor position
- ESC[u | Move cursor to previously saved position
Sequence parameters are in decimal, if omitted zero is assumed. Where the parameter is a count {n}, zero is treated as 1. Columns and rows start at 1.
{color} is a number between 0 and 15, corresponding to black, red, green, yellow, blue, magenta, cyan, white)
These are the sequences generated for special keys:
- F1: ESC O P
- F2: ESC O Q
- F3: ESC O R
- F4: ESC O S
- F5: ESC O T
- F6: ESC O U
- F7: ESC O V
- F8: ESC O W
- F9: ESC O X
- F10: ESC O Y
- Home: ESC [ H
- End: ESC [ K
- Up: ESC [ A
- Down: ESC [ B
- Right: ESC [ C
- Left: ESC [ D
- Del: 0x7F
The following ALT letter combinations are used for local functions:
- ALT C: Enter configuration screen.
- ALT L: Changes between on-line mode and local mode (characters typed are treated as received characters).
- ALT R: Receive a file (TODO)
- ALT T: Transmit a file (TODO)
The configuration screen is entered by typing ALT C and left by typing ESC.
To navigate between fields, use the up and down arrows.
To change a field, use space or + to change to the next value and - to change to the previous value.
RPTerm is inspired and based on picoterm (https://github.com/RC2014Z80/picoterm) from Sheila Dixon (https://peacockmedia.software).
VGA output uses the wonderful picovga (http://www.breatharian.eu/hw/picovga/index_en.html) by Miroslav Nemecek.
Key sequences based on propeller-vt100 (https://github.com/maccasoft/propeller-vt100-terminal) by Marco Maccaferri.
The software was developed under Windows, with the standard Raspberry Pi Pico C/C++ SDK v2.0.0, with tinyusb v0.16.0.
It should compile under other operating systems supported by the SDK.
Testing was done with a RP2040-Zero, but it should not be hard to get it to work on other RP2040 boards with the following pins available:
- Eight contiguous GPIOs (I am using GP0 to GP7)
- One GPIO for Composite Sync (since v0.7 I am using GP27)
- One GPIO for the buzzer (if you want to support the BEL control code, I am using GP29)
- One GPIO for a status LED (optional, since v0.7 I am using GP28)
- UART pins (I am using UART0 at GPIO 12 & 13)
- SPI pins for SD Card (I am using GPIO8 to GPIO11, SPI1)
Hardware configuration is at the hwconfig.h file. The hardware directory has details for a few boards.
Hardware was slightly changed in version 0.7 to include SD Card support:
- Composite Sync was moved from GP8 to GPIO27
- LED was moved from GP11 to GPIO28.
Microcontroller projects must have a blinking LED, right?
The (optional) status LED blinks to indicate that the firmware is executing. It will blink more rapidly while receiving data.
This is (and will be for some time) a work in progress.
The basics are in place: vga, serial and keyboard support. Basic terminal emulation is working. I'm still revising/rewriting it and it needs a lot of testing.
Scrolling the screen is done by brute force. Having a table with line address will speed it up, but requires changing assembly code in pico_vga (and hoping I will not mess up the timing).
The configuration screen is working, but config is not saved yet.
Config will be stored in the SD card. Special keys will be used to send and receive text files from the SD.