Pi 400 KB

README.md

Raspberry Pi 400 as a USB HID Keyboard

⚠️ This gist has been deprecated. See this repo instead: https://github.com/Gadgetoid/pi400kb

Hook your Pi 400 up to your PC somehow, using a USB Type-C cable into the power port. Anker make good ones- I used a 3m white one for my tests.

Setup

Add dtoverlay=dwc2 to /boot/config.txt

Reboot!

Run sudo modprobe libcomposite

RUn wget https://gist.github.com/Gadgetoid/5a8ceb714de8e630059d30612503653f/raw/35fde8da7fcd88e7ccd3913c729f2b14bbd4a0a7/pi400kb

Run sudo ./pi400kb

YOUR PI 400 IS NOW A FREAKING KEYBOARD FOR YOUR PC WHAAAAT!?

Your keyboard input will be detached from your Pi while it's forwarded to your host computer.

Press Ctrl + Raspberry to exit and restore your keyboard on the Pi.

gadget-hid.c

#include "gadget-hid.h"
#include <errno.h>
#include <stdio.h>
#include <linux/usb/ch9.h>
#include <usbg/usbg.h>
#include <usbg/function/hid.h>
#include <usbg/function/midi.h>

static char report_desc[] = {
	0x05, 0x01,
	0x09, 0x06,
	0xA1, 0x01,
	0x05, 0x07,
	0x19, 0xe0,
	0x29, 0xe7,
	0x15, 0x00,
	0x25, 0x01,

	0x75, 0x01,
	0x95, 0x08,
	0x81, 0x02,
	0x95, 0x01,
	0x75, 0x08,
	0x81, 0x01,
	0x95, 0x03,
	0x75, 0x01,

	0x05, 0x08,
	0x19, 0x01,
	0x29, 0x03,
	0x91, 0x02,
	0x95, 0x05,
	0x75, 0x01,
	0x91, 0x01,
	0x95, 0x06,

	0x75, 0x08,
	0x15, 0x00,
	0x26, 0xff,
	0x00, 0x05,
	0x07, 0x19,
	0x00, 0x2a,
	0xff, 0x00,
	0x81, 0x00, // Input (Data, Array, Abs)
	0xc0 // End collection
};

int initUSB() {
    int ret = -EINVAL;
    int usbg_ret;

    struct usbg_gadget_attrs g_attrs = {
        .bcdUSB = 0x0200,
        .bDeviceClass = USB_CLASS_PER_INTERFACE,
        .bDeviceSubClass = 0x00,
        .bDeviceProtocol = 0x00,
        .bMaxPacketSize0 = 64, /* Max allowed ep0 packet size */
        .idVendor = VENDOR,
        .idProduct = PRODUCT,
        .bcdDevice = 0x0001, /* Verson of device */
    };

    struct usbg_gadget_strs g_strs = {
        .serial = "0123456789", /* Serial number */
        .manufacturer = "Pimoroni", /* Manufacturer */
        .product = "Keybow" /* Product string */
    };

    struct usbg_config_strs c_strs = {
        .configuration = "1xHID"
    };

    struct usbg_f_midi_attrs midi_attrs = {
        .index = 1,
        .id = "usb1",
        .buflen = 128,
        .qlen = 16,
        .in_ports = 1,
        .out_ports = 1
    };

    struct usbg_f_hid_attrs f_attrs = {
        .protocol = 1,
        .report_desc = {
            .desc = report_desc,
            .len = sizeof(report_desc),
        },
        .report_length = 16,
        .subclass = 0,
    };

    usbg_ret = usbg_init("/sys/kernel/config", &s);
    if (usbg_ret != USBG_SUCCESS) {
        fprintf(stderr, "Error on usbg init\n");
        fprintf(stderr, "Error: %s : %s\n", usbg_error_name(usbg_ret),
                usbg_strerror(usbg_ret));
        goto out1;
    }

    usbg_ret = usbg_create_gadget(s, "g1", &g_attrs, &g_strs, &g);
    if (usbg_ret != USBG_SUCCESS) {
        fprintf(stderr, "Error creating gadget\n");
        fprintf(stderr, "Error: %s : %s\n", usbg_error_name(usbg_ret),
                usbg_strerror(usbg_ret));
        goto out2;
    }

    usbg_ret = usbg_create_function(g, USBG_F_HID, "usb0", &f_attrs, &f_hid);
    if (usbg_ret != USBG_SUCCESS) {
        fprintf(stderr, "Error creating function: USBG_F_HID\n");
        fprintf(stderr, "Error: %s : %s\n", usbg_error_name(usbg_ret),
                usbg_strerror(usbg_ret));
        goto out2;
    }

    usbg_ret = usbg_create_config(g, 1, "config", NULL, &c_strs, &c);
    if (usbg_ret != USBG_SUCCESS) {
        fprintf(stderr, "Error creating config\n");
        fprintf(stderr, "Error: %s : %s\n", usbg_error_name(usbg_ret),
                usbg_strerror(usbg_ret));
        goto out2;
    }

    usbg_ret = usbg_add_config_function(c, "keyboard", f_hid);
    if (usbg_ret != USBG_SUCCESS) {
        fprintf(stderr, "Error adding function: keyboard\n");
        fprintf(stderr, "Error: %s : %s\n", usbg_error_name(usbg_ret),
                usbg_strerror(usbg_ret));
        goto out2;
    }

    usbg_ret = usbg_enable_gadget(g, DEFAULT_UDC);
    if (usbg_ret != USBG_SUCCESS) {
        fprintf(stderr, "Error enabling gadget\n");
        fprintf(stderr, "Error: %s : %s\n", usbg_error_name(usbg_ret),
                usbg_strerror(usbg_ret));
        goto out2;
    }

    ret = 0;

out2:
    usbg_cleanup(s);
    s = NULL;

out1:
    return ret;
}

int cleanupUSB(){
    if(g){
        usbg_disable_gadget(g);
        usbg_rm_gadget(g, USBG_RM_RECURSE);
    }
    if(s){
        usbg_cleanup(s);
    }
    return 0;
}

gadget-hid.h

#include <linux/usb/ch9.h>
#include <usbg/usbg.h>
#include <usbg/function/hid.h>

#define VENDOR          0x04d9
#define PRODUCT         0x0007
#define HID_REPORT_SIZE 8

usbg_state *s;
usbg_gadget *g;
usbg_config *c;
usbg_function *f_hid;

int initUSB();
int cleanupUSB();

Makefile

CFLAGS_ALL=-I../libusbgx/build/include -I../bcm2835-1.68/build/include -L../bcm2835-1.68/build/lib -I../lua-5.4.0/src -L../libusbgx/build/lib -L../libserialport/build/lib -L../lua-5.4.0/src -lpng -lz -lpthread -llua -lm -lbcm2835 -ldl

pi400: CFLAGS+=-static $(CFLAGS_ALL) -lusbgx -lconfig -DPI400_USB
pi400: pi400.c gadget-hid.c
	$(CC)  $^ $(CFLAGS) -o $@


pi400test: CFLAGS+=-static $(CFLAGS_ALL) -lusbgx -lconfig
pi400test: pi400.c gadget-hid.c
	$(CC)  $^ $(CFLAGS) -o $@


clean:
	-rm pi400
	-rm pi400test

pi400.c

#include "pi400.h"

#include "gadget-hid.h"

#include <sys/ioctl.h>
#include <linux/hidraw.h>
#include <linux/input.h>
#include <signal.h>
#include <errno.h>
#include <stdio.h>
#include <fcntl.h>
#include <stdio.h>
#include <lua.h>
#include <lualib.h>
#include <lauxlib.h>
#include <unistd.h>


#define KEYBOARD_DEV "/dev/input/by-id/usb-_Raspberry_Pi_Internal_Keyboard-event-kbd"

#define HID_REPORT_SIZE 8
#define GRAB 1
#define UNGRAB 0

int hid_output;
volatile int running = 0;
int key_index = 0;

void signal_handler(int dummy) {
    running = 0;
}

int find_hidraw_device() {
    int fd;
    int ret;
    struct hidraw_devinfo hidinfo;
    char path[20];

    for(int x = 0; x < 16; x++){
	sprintf(path, "/dev/hidraw%d", x);
        if ((fd = open(path, O_RDWR | O_NONBLOCK)) == -1) {
            continue;
        }

        ret = ioctl(fd, HIDIOCGRAWINFO, &hidinfo);

        if(hidinfo.vendor == VENDOR && hidinfo.product == PRODUCT) {
	    printf("Found keyboard at: %s\n", path);
	    return fd;
        }

	close(fd);
    }

    return -1;
}

int main() {
    int ret;
    int fd;
    int uinput_fd;
    unsigned char buf[HID_REPORT_SIZE];

    fd = find_hidraw_device();
    if(fd == -1) {
	printf("Failed to open keyboard device\n");
	return 1;
    }
    ret = initUSB();

    uinput_fd = open(KEYBOARD_DEV, O_RDONLY);
    ioctl(uinput_fd, EVIOCGRAB, UNGRAB);
    usleep(500000);
    ioctl(uinput_fd, EVIOCGRAB, GRAB);

    do {
        hid_output = open("/dev/hidg0", O_WRONLY | O_NDELAY);
    } while (hid_output == -1 && errno == EINTR);
    if (hid_output == -1){
        printf("Error opening /dev/hidg0 for writing.\n");
        return 1;
    }

    printf("Running...\n");
    running = 1;
    signal(SIGINT, signal_handler);

    while (running){
	int c = read(fd, buf, HID_REPORT_SIZE);
	if(c != HID_REPORT_SIZE){
		continue;
	}
	for(int x = 0; x < HID_REPORT_SIZE; x++)
	{
		printf("%x ", buf[x]);
	}
	printf("\n");
	write(hid_output, buf, HID_REPORT_SIZE);
        usleep(1000);

	if(buf[0] == 0x09){
	    running = 0;
	    break;
	}
    } 

    for(int x = 0; x < HID_REPORT_SIZE; x++){
	buf[x] = 0;
    };

    write(hid_output, buf, HID_REPORT_SIZE);

    ioctl(uinput_fd, EVIOCGRAB, UNGRAB);
    close(uinput_fd);

    printf("Cleanup USB\n");
    cleanupUSB();

    return 0;
}

pi400.h

#include <bcm2835.h>
#include <pthread.h>

int initUSB();
int main();
void sendHIDReport();

pi400kb

@Gadgetoid
Move to git repo from gist is a good move.
I followed instruction and was able to build, and it works.
Created new issue on two warnings:
Gadgetoid/pi400kb#5

Hopefully I'll find the time to address some of the roadmap issues I've set up and make it easier to get other mice/keyboards working. Pretty sure a Pi 4 could also run this?

I've searched for hours, and haven't yet found a single project that allows me to use the Pi4 400 keyboard as an actual keyboard for any device, including this frequently recommended repository, unfortunately. A very simple use case is plugging the 400 into an actual Raspberry Pi4 and using it as a keyboard for that device. Having to carry two keyboards seems silly, no?

Having to power up the Pi4 400 (eg: "boot" it) is not a workable solution, since it requires a monitor to be attached, then a console, then a login, and running the binary. Yes, you could roll that into the bootup and make it headless, but then... you're still booting the RPi4 OS just to redirect keys. You can't just plug the 400 into a machine and get a working keyboard, that's the catch here, and why this, and dozens of other hacks, bodges and workarounds fall apart.

Why can't the physical hardware itself, be presented to the USB bus of the client system, as a HID device? It's already presented as a HID device to the underlying OS itself, when booting natively on the 400. IOW, USB-A (400 side) to USB-A (client machine), should present itself as a HID device to the receiving machine. No need to power it up, boot it or run an OS on the device itself.

Why is this a hurdle nobody has crossed yet?

Because a Pi400 is not intended to be used as a keyboard, additional software is needed.
You outlined the solution already, headless and hook into boutup.
My Pi400 always boots as KVM switch directly into loptop it is connected to:
https://forums.raspberrypi.com/viewtopic.php?f=140&t=321840

Why not use 18$ Raspberry keyboard for your needs?
https://www.raspberrypi.com/products/raspberry-pi-keyboard-and-hub/

Why can't the physical hardware itself, be presented to the USB bus of the client system, as a HID device? It's already presented as a HID device to the underlying OS itself, when booting natively on the 400. IOW, USB-A (400 side) to USB-A (client machine), should present itself as a HID device to the receiving machine. No need to power it up, boot it or run an OS on the device itself.

Is this a joke?