Updated README

updated README to add some instructions for connecting to the PicoCalc using minicom. Mostly I find instructions for windows users, so hopefully this will be helpful to someone.

Author: aefarrell

README.md

@@ -9,3 +9,92 @@ The structure is like this:
 - `art\` BASIC code for generating cool visualizations and art
 - `utils\` useful utilities
 - `toys\` little toy programs
+
+## Transferring with the PicoCalc
+
+The fastest way to transfer files, in bulk, is via the SD card -- if you have an SD card reader. Alternatively you can connect to the PicoCalc via the serial connection. First turn on the PicoCalc and connect to your computer via the USB-C port on the PicoCalc.
+
+I use linux at home, and use [minicom](https://salsa.debian.org/minicom-team/minicom) to connect via the terminal. The first steps are to determine which device the PicoCalc has connected as, and add the appropriate permissions for the user to connect.
+
+### Identifying the PicoCalc serial device
+
+To find the device the PicoCalc has been mapped to
+
+~~~bash
+
+dmesg | grep -i uart
+
+~~~
+
+Scrolling through the output I find the following
+
+~~~
+[ 1053.104717] ch341 1-1:1.0: ch341-uart converter detected
+[ 1053.105166] usb 1-1: ch341-uart converter now attached to ttyUSB0
+~~~
+
+> [!TIP]
+> I use popOS at home and I found initially that the PicoCalc would connect, attach to ttyUSB0, and immediately disconnect. The solution was to uninstall `brltty`.
+
+Which is the PicoCalc being detected and attached to `/dev/ttyUSB0`. The user requires read-write permission to connect to the device, which can be accomplished by adding it to the group the device is in with `ls`.
+
+~~~bash
+
+ls -lah /dev/ttyUSB0
+
+~~~
+
+
+On my machine it is in the group `dialout`
+
+~~~
+crw-rw---- 1 root dialout 188, 0 Dec  3 19:06 /dev/ttyUSB0
+~~~
+
+After the user has been added to the group (and possibly after logging out and back in), the PicoCalc can be connected to without having to use `sudo`.
+
+### Configuring minicom
+
+Minicom will look for a config file in `$HOME` when given an appropriate name, and if one isn't found it will create it, e.g. this creates a config file named 'picocalc'
+
+~~~bash
+
+minicom picocalc
+
+~~~
+
+From within minicom hit `Ctrl-A` followed by `o` to open the configuration menu and adjust the default settings to the PicoCalc. This will save a `.minirc.picocalc` in `$HOME`, mine looks like this:
+
+~~~
+# Machine-generated file - use setup menu in minicom to change parameters.
+pu port             /dev/ttyUSB0
+pu rtscts           No 
+~~~
+
+### Connecting to the PicoCalc
+
+Once minicom is configured, a serial connection can be opened by simply calling the config file
+
+~~~bash
+
+minicom picocalc
+
+~~~
+
+This opens a terminal and any keystrokes are mirrored on the PicoCalc. To send a file from the computer to the PicoCalc, first enter the following into the PicoCalc
+
+~~~
+xmodem receive "your/directory/and/file"
+~~~
+
+Then hit `Ctrl-A` followed by `s` in minicom and select the file you wish to send. Since minicom is connected as a terminal this all be done in the same terminal window.
+
+To do the reverse, first enter the following into the PicoCalc
+
+~~~
+xmodem send "your/directory/and/file"
+~~~
+
+Then hit `Ctrl-A` followed by `r` in minicom and give the filename to be saved locally. Again, with minicom connected as a terminal this can all be done in the same window.
+
+Transferring programs and text files with [xmodem](https://en.wikipedia.org/wiki/XMODEM) is relatively fast, but anything large like an image file or music, is fairly slow and is probably worth transferring back and forth via the SD card.