ZMK firmware

README.md

@@ -10,4 +10,35 @@ Compared to the original Egret, besides having two thumb buttons per side, the R
 
 ![Re-gret Underglow](images/IMG_0812.jpeg)
 
+## Build guide
+
 Check the docs for a [PCB Build Guide](docs/pcb_build_guide.md) and [Case Build Guide](docs/case_build_guide.md).
+
+## RGB Underglow
+
+I powered the RGB underglow directly from the USB 5v, so it will automagically turn itself off when in wireless bluetooth mode. There's no need for ZMK's [External Power Control](https://zmk.dev/docs/behaviors/power#external-power-control) because you physically can't run the LEDs from battery power even if you wanted to. There's a [clever trick](https://hackaday.com/2017/01/20/cheating-at-5v-ws2812-control-to-use-a-3-3v-data-line/) using a diode that allows the 5v LEDs to be controlled by the Xiao's 3.3v logic. 
+
+## Firmware
+
+### ZMK
+
+Copy the contents of `firmware/zmk/config/boards/shields/regret/` into `[your-zmk-config]/config/boards/shields/regret/`
+
+Be advised that right now the underglow only works on the XIAO nRF52840 board, and does not work on the XIAO RP2040 (although it [might in the future](https://github.com/zmkfirmware/zmk/issues/1085)). The original XIAO SAMD21 should work but I haven't tested it.
+
+| Board                 | Chip     | USB Wired          | Bluetooth Wireless | RGB Underglow      | Comments                                                     |
+| --------------------- | -------- | ------------------ | ------------------ | ------------------ | ------------------------------------------------------------ |
+| XIAO                  | SAMD21   | :white_check_mark: | :x:                | :x:                | Should work but untested                                     |
+| Adafruit Qt PY        | SAMD21   | :white_check_mark: | :x:                | :x:                | Should work but untested                                     |
+| XIAO BLE              | nRF52840 | :white_check_mark: | :white_check_mark: | :white_check_mark: |                                                              |
+| XIAO RP2040           | RP2040   | :white_check_mark: | :x:                | :x: for now        | Underglow [maybe someday](https://github.com/zmkfirmware/zmk/issues/1085) |
+| Adafruit Qt PY RP2040 | RP2040   | :white_check_mark: | :x:                | :x: for now        | Should work but untested                                     |
+
+### QMK
+
+I have not written QMK firmware yet, but maybe I will for the RP2040.
+
+## Related
+
+* I cribbed the Xiao footprint, pogo pin idea, and battery from the [revxlp](https://gitlab.com/lpgalaxy/revxlp)
+* My original 36 key [Egret](https://github.com/rschenk/egret) was the starting point

firmware/zmk/config/boards/shields/regret/Kconfig.defconfig

@@ -0,0 +1,6 @@
+if SHIELD_REGRET
+
+config ZMK_KEYBOARD_NAME
+    default "Re-gret"
+
+endif

firmware/zmk/config/boards/shields/regret/Kconfig.shield

@@ -0,0 +1,3 @@
+config SHIELD_REGRET
+    def_bool $(shields_list_contains,regret)
+    select SPI

firmware/zmk/config/boards/shields/regret/boards/seeeduino_xiao.conf

@@ -0,0 +1,2 @@
+CONFIG_SPI=y
+CONFIG_ZMK_KSCAN_MATRIX_POLLING=y

firmware/zmk/config/boards/shields/regret/boards/seeeduino_xiao_ble.conf

@@ -0,0 +1 @@
+CONFIG_SPI=y

firmware/zmk/config/boards/shields/regret/boards/seeeduino_xiao_ble.overlay

@@ -0,0 +1,66 @@
+/* Shift register */
+
+&spi2_default {
+    group1 {
+        psels = <NRF_PSEL(SPIM_SCK, 1, 13)>,
+            <NRF_PSEL(SPIM_MOSI, 1, 15)>;
+    };
+};
+
+&spi2_sleep {
+    group1 {
+        psels = <NRF_PSEL(SPIM_SCK, 1, 13)>,
+            <NRF_PSEL(SPIM_MOSI, 1, 15)>;
+    };
+};
+
+
+/* LED underglow */
+
+#include <dt-bindings/led/led.h>
+
+&pinctrl {
+    spi3_default: spi3_default {
+        group1 {
+            psels = <NRF_PSEL(SPIM_MOSI, 0, 2)>;
+        };
+    };
+
+    spi3_sleep: spi3_sleep {
+        group1 {
+            psels = <NRF_PSEL(SPIM_MOSI, 0, 2)>;
+            low-power-enable;
+        };
+    };
+};
+
+&spi3 {
+  compatible = "nordic,nrf-spim";
+  status = "okay";
+
+  pinctrl-0 = <&spi3_default>;
+  pinctrl-1 = <&spi3_sleep>;
+  pinctrl-names = "default", "sleep";
+
+  led_strip: ws2812@0 {
+    compatible = "worldsemi,ws2812-spi";
+
+    /* SPI */
+    reg = <0>; /* ignored, but necessary for SPI bindings */
+    spi-max-frequency = <4000000>;
+
+    /* WS2812 */
+    chain-length = <11>; /* number of LEDs */
+    spi-one-frame = <0x70>;
+    spi-zero-frame = <0x40>;
+    color-mapping = <LED_COLOR_ID_GREEN
+                          LED_COLOR_ID_RED
+                          LED_COLOR_ID_BLUE>;
+  };
+};
+
+/ {
+    chosen {
+        zmk,underglow = &led_strip;
+    };
+};

firmware/zmk/config/boards/shields/regret/regret.conf

@@ -0,0 +1,6 @@
+# Uncomment the following lines to enable RGB underglow
+# CONFIG_ZMK_RGB_UNDERGLOW=y
+CONFIG_WS2812_STRIP=y
+CONFIG_ZMK_RGB_UNDERGLOW_EXT_POWER=n
+CONFIG_ZMK_RGB_UNDERGLOW_AUTO_OFF_USB=y
+

firmware/zmk/config/boards/shields/regret/regret.keymap

@@ -0,0 +1,22 @@
+#include <behaviors.dtsi>
+#include <dt-bindings/zmk/keys.h>
+
+/ {
+    keymap {
+        compatible = "zmk,keymap";
+
+        default_layer {
+// ------------------------------------------------------------------------------------------------------
+// |    Q    |    W    |    E    |    R    |    T    |    Y    |    U    |    I    |    O    |    P    |
+// |    A    |    S    |    D    |    F    |    G    |    H    |    J    |    K    |    L    |    ;    |
+// |    Z    |    X    |    C    |    V    |    B    |    N    |    M    |    ,    |    .    |    /    |
+//                               |   ESC   |  SPACE  | RETURN  |   BSPC  |
+            bindings = <
+    &kp Q    &kp W     &kp E     &kp R     &kp T     &kp Y     &kp U     &kp I     &kp O     &kp P
+    &kp A    &kp S     &kp D     &kp F     &kp G     &kp H     &kp J     &kp K     &kp L     &kp SEMI
+    &kp Z    &kp X     &kp C     &kp V     &kp B     &kp N     &kp M     &kp COMMA &kp DOT   &kp FSLH
+                                 &kp ESC   &kp SPACE &kp RET   &kp BSPC
+            >;
+        };
+    };
+};

firmware/zmk/config/boards/shields/regret/regret.overlay

@@ -0,0 +1,61 @@
+#include <dt-bindings/zmk/matrix_transform.h>
+
+&xiao_serial { status = "disabled"; };
+
+&xiao_spi {
+    status = "okay";
+    cs-gpios = <&xiao_d 9 GPIO_ACTIVE_LOW>;
+    shifter: 595@0 {
+        compatible = "zmk,gpio-595";
+        status = "okay";
+        gpio-controller;
+        spi-max-frequency = <200000>;
+        reg = <0>;
+        #gpio-cells = <2>;
+        ngpios = <8>;
+    };
+};
+
+/ {
+    chosen {
+        zmk,kscan = &kscan0;
+        zmk,matrix_transform = &default_transform;
+    };
+
+    default_transform: keymap_transform_0 {
+        compatible = "zmk,matrix-transform";
+        columns = <5>;
+        rows = <8>;
+        map = <
+RC(0,0) RC(0,1) RC(0,2) RC(0,3) RC(0,4) RC(4,4) RC(4,3) RC(4,2) RC(4,1) RC(4,0)
+RC(1,0) RC(1,1) RC(1,2) RC(1,3) RC(1,4) RC(5,4) RC(5,3) RC(5,2) RC(5,1) RC(5,0)
+RC(2,0) RC(2,1) RC(2,2) RC(2,3) RC(2,4) RC(6,4) RC(6,3) RC(6,2) RC(6,1) RC(6,0)
+                        RC(3,3) RC(3,4) RC(7,4) RC(7,3)
+        >;
+    };
+
+    kscan0: kscan_0 {
+        compatible = "zmk,kscan-gpio-matrix";
+        diode-direction = "row2col";
+        wakeup-source;
+
+        col-gpios
+            = <&xiao_d 1 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)>
+            , <&xiao_d 2 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)>
+            , <&xiao_d 3 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)>
+            , <&xiao_d 4 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)>
+            , <&xiao_d 5 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)>
+            ;
+
+        row-gpios
+            = <&shifter 7 GPIO_ACTIVE_HIGH>
+            , <&shifter 6 GPIO_ACTIVE_HIGH>
+            , <&shifter 5 GPIO_ACTIVE_HIGH>
+            , <&shifter 4 GPIO_ACTIVE_HIGH>
+            , <&shifter 0 GPIO_ACTIVE_HIGH>
+            , <&shifter 1 GPIO_ACTIVE_HIGH>
+            , <&shifter 2 GPIO_ACTIVE_HIGH>
+            , <&shifter 3 GPIO_ACTIVE_HIGH>
+            ;
+    };
+};

firmware/zmk/config/boards/shields/regret/regret.zmk.yml

@@ -0,0 +1,8 @@
+file_format: "1"
+id: regret
+name: Re-gret
+type: shield
+url: https://github.com/rschenk/regret
+requires: [seeed_xiao]
+features:
+  - keys