{"id":16732,"date":"2021-06-02T22:18:14","date_gmt":"2021-06-03T02:18:14","guid":{"rendered":"https:\/\/scruss.com\/blog\/?p=16732"},"modified":"2021-06-02T22:18:17","modified_gmt":"2021-06-03T02:18:17","slug":"cardkb-mini-keyboard-with-micropython","status":"publish","type":"post","link":"https:\/\/scruss.com\/blog\/2021\/06\/02\/cardkb-mini-keyboard-with-micropython\/","title":{"rendered":"CardKB mini keyboard with MicroPython"},"content":{"rendered":"\n
\"small
it really is the size of a credit card
(running with a SeeedStudio Wio Terminal<\/a>)<\/figcaption><\/figure>\n\n\n\n

I got one of these CardKB Mini Keyboard<\/a>s to see if I could use it for small interactives with MicroPython devices. It’s very small, and objectively not great as a mass data entry tool. “Better than a Pocket C.H.I.P. keyboard<\/em>” is how I’d describe the feel. It’s also pretty reliable.<\/p>\n\n\n\n

It’s got an I\u00c2\u00b2C Grove<\/a> connector, and its brains are an ATMega chip just like an Arduino. It’s strictly an ASCII keyboard: that is, it sends the 8-bit ASCII code of the key combination you pressed. It doesn’t send scan codes like a PC keyboard. The driver source is in the CardKB m5-docs<\/a>, so if you really felt ambitious you could write a scan code-like firmware for yourself.<\/p>\n\n\n\n

The device appears at I\u00c2\u00b2C peripheral address 95, and returns a single byte when polled. That byte’s either 0 if no key was pressed, or the character code of what was pressed. The Esc<\/kbd> key returns chr(27), and Enter<\/kbd> returns CR. If you poll the keyboard too fast it seems to lose the plot a little, so a tiny delay seems to help<\/p>\n\n\n\n

Here’s a small demo for MicroPython that acts as the world’s worst typewriter:<\/p>\n\n\n

\n# M5Stack CardKB tiny keyboard - scruss, 2021-06\n# MicroPython - Raspberry Pi Pico\n\nfrom machine import Pin, I2C\nfrom time import sleep_ms\n\ni2c = I2C(1, scl=Pin(7), sda=Pin(6))\ncardkb = i2c.scan()[0]  # should return 95\nif cardkb != 95:\n    print("!!! Check I2C config: " + str(i2c))\n    print("!!! CardKB not found. I2C device", cardkb,\n          "found instead.")\n    exit(1)\n\nESC = chr(27)\nNUL = '\\x00'\nCR = "\\r"\nLF = "\\n"\nc = ''\n\nprint("*** APPALLING TYPEWRITER ***")\nprint("** Type stuff, Esc to end **")\n\nwhile (c != ESC):\n    # returns NUL char if no character read\n    c = i2c.readfrom(cardkb, 1).decode()\n    if c == CR:\n        # convert CR return key to LF\n        c = LF\n    if c != NUL or c != ESC:\n        print(c, end='')\n    sleep_ms(5)\n<\/pre><\/div>\n\n\n
And here’s the CircuitPython version. It has annoying tiny differences. It won’t let me use the I\u00c2\u00b2C Grove connector on the Wio Terminal for some reason, but it does work much the same:<\/p>\n\n\n
\n# M5Stack CardKB tiny keyboard - scruss, 2021-06\n# CircuitPython - SeeedStudio Wio Terminal\n# NB: can't use Grove connector under CPY because CPY\n\nimport time\nimport board\nimport busio\n\ni2c = busio.I2C(board.SCL, board.SDA)\n\nwhile not i2c.try_lock():\n    pass\n\ncardkb = i2c.scan()[0]  # should return 95\nif cardkb != 95:\n    print("!!! Check I2C config: " + str(i2c))\n    print("!!! CardKB not found. I2C device", cardkb,\n          "found instead.")\n    exit(1)\n\nESC = chr(27)\nNUL = '\\x00'\nCR = "\\r"\nLF = "\\n"\nc = ''\nb = bytearray(1)\n\n# can't really clear screen, so this will do\nfor i in range(12):\n    print()\nprint("*** APPALLING TYPEWRITER ***")\nprint("** Type stuff, Esc to end **")\nfor i in range(8):\n    print()\n\nwhile (c != ESC):\n    # returns NUL char if no character read\n    i2c.readfrom_into(cardkb, b)\n    c = b.decode()\n    if c == CR:\n        # convert CR return key to LF\n        c = LF\n    if c != NUL or c != ESC:\n        print(c, end='')\n    time.sleep(0.005)\n\n# be nice, clean up\ni2c.unlock()\n<\/pre><\/div>\n\n\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
I got one of these CardKB Mini Keyboards to see if I could use it for small interactives with MicroPython devices. It’s very small, and objectively not great as a mass data entry tool. “Better than a Pocket C.H.I.P. keyboard” is how I’d describe the feel. It’s also pretty reliable. It’s got an I\u00c2\u00b2C Grove […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[7],"tags":[3105,2208,3165,3094],"class_list":["post-16732","post","type-post","status-publish","format-standard","hentry","category-computers-suck","tag-circuitpython","tag-electronics","tag-keyboard","tag-micropython"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/pQNZZ-4lS","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/scruss.com\/blog\/wp-json\/wp\/v2\/posts\/16732","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/scruss.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/scruss.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/scruss.com\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/scruss.com\/blog\/wp-json\/wp\/v2\/comments?post=16732"}],"version-history":[{"count":5,"href":"https:\/\/scruss.com\/blog\/wp-json\/wp\/v2\/posts\/16732\/revisions"}],"predecessor-version":[{"id":16739,"href":"https:\/\/scruss.com\/blog\/wp-json\/wp\/v2\/posts\/16732\/revisions\/16739"}],"wp:attachment":[{"href":"https:\/\/scruss.com\/blog\/wp-json\/wp\/v2\/media?parent=16732"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/scruss.com\/blog\/wp-json\/wp\/v2\/categories?post=16732"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/scruss.com\/blog\/wp-json\/wp\/v2\/tags?post=16732"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}