co2minimon

commit f215c8bfb3234cf083fb492cf27b8cbf8fd8fe4e
Author: amin <dev@aminmesbah.com>
Date:   Tue, 28 Dec 2021 02:54:53 +0000

Get data from the co2mini through the hidraw api

But we fail to decode it. It looks [1] like they may have changed the
encryption system in the version of the hardware I have. I may need to
follow Henryk's steps and reverse engineer the new version.

[1]: https://hackaday.io/project/5301-reverse-engineering-a-low-cost-usb-co-monitor/discussion-168652

FossilOrigin-Name: ab94b787d128884e2f7c73cc082f6350256cb644d5dcede2e1e201af80f0e781
Diffstat:
A
.gitignore
 | 
1
+
A
99-co2mini.rules
 | 
5
+++++
A
README.md
 | 
5
+++++
A
main.c
 | 
101
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

4 files changed, 112 insertions(+), 0 deletions(-)
diff --git a/.gitignore b/.gitignore
@@ -0,0 +1 @@
+a.out
diff --git a/99-co2mini.rules b/99-co2mini.rules
@@ -0,0 +1,5 @@
+ACTION=="remove", GOTO="co2mini_end"
+
+SUBSYSTEMS=="usb", KERNEL=="hidraw*", ATTRS{idVendor}=="04d9", ATTRS{idProduct}=="a052", GROUP="wheel", MODE="0660", SYMLINK+="co2mini%n", GOTO="co2mini_end"
+
+LABEL="co2mini_end"
diff --git a/README.md b/README.md
@@ -0,0 +1,5 @@
+Put the udev rules in /etc/udev/rules.d/, then reload the rules with:
+
+```
+# udevadm control --reload-rules && udevadm trigger
+```
diff --git a/main.c b/main.c
@@ -0,0 +1,101 @@
+#include <assert.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdint.h>
+
+#include <fcntl.h>     // open()
+#include <sys/ioctl.h> // ioctl()
+#include <unistd.h>    // close()
+
+#include <linux/hidraw.h>
+
+typedef uint8_t buffer[8];
+
+// Made possible by Henryk Plötz' excellent work:
+// https://hackaday.io/project/5301-reverse-engineering-a-low-cost-usb-co-monitor
+
+// references
+// https://www.kernel.org/doc/Documentation/hid/hidraw.txt
+int main(void) {
+    // NOTE: Included udev rules create this symlink to the appropriate hidraw
+    // entry.
+    int device_handle = open("/dev/co2mini0", O_RDWR);
+    if (device_handle < 0) {
+        printf("ERROR: Failed to open hid\n");
+        return 1;
+    }
+
+    buffer key = {0};
+    int result = ioctl(device_handle, HIDIOCSFEATURE(sizeof(key)), key);
+    if (result < 0 || result != sizeof(buffer)) {
+        printf("ERROR: Failed to send feature report\n");
+        return 1;
+    }
+
+    while (true) {
+        buffer data = {0};
+        int bytes_read = read(device_handle, &data, sizeof(buffer));
+        if (bytes_read < 0 && (errno == EAGAIN || errno == EINPROGRESS)) {
+            bytes_read = 0;
+        } else {
+            assert(bytes_read == sizeof(buffer));
+        }
+
+        if (bytes_read == sizeof(buffer)) {
+            buffer decoded = {0};
+            {
+                {
+                    uint8_t tmp;
+                    tmp = data[0]; data[0] = data[2]; data[2] = tmp;
+                    tmp = data[1]; data[1] = data[4]; data[4] = tmp;
+                    tmp = data[3]; data[3] = data[7]; data[7] = tmp;
+                    tmp = data[5]; data[5] = data[6]; data[6] = tmp;
+                }
+
+                for (int i = 0; i < sizeof(buffer); ++i) {
+                    data[i] ^= key[i];
+                }
+
+                {
+                    uint8_t tmp = (data[7] << 5);
+                    decoded[7] = (data[6] << 5) | (data[7] >> 3);
+                    decoded[6] = (data[5] << 5) | (data[6] >> 3);
+                    decoded[5] = (data[4] << 5) | (data[5] >> 3);
+                    decoded[4] = (data[3] << 5) | (data[4] >> 3);
+                    decoded[3] = (data[2] << 5) | (data[3] >> 3);
+                    decoded[2] = (data[1] << 5) | (data[2] >> 3);
+                    decoded[1] = (data[0] << 5) | (data[1] >> 3);
+                    decoded[0] = tmp | (data[0] >> 3);
+                }
+
+                buffer dumb_proprietary_bullshit_secret_word = "Htemp99e";
+                for (int i = 0; i < sizeof(buffer); ++i)
+                {
+                    decoded[i] -= (dumb_proprietary_bullshit_secret_word[i] << 4) | (dumb_proprietary_bullshit_secret_word[i] >> 4);
+                }
+            }
+
+            if (decoded[4] != 0x0d) {
+                printf("BAD DATA: ");
+            } else {
+                switch(decoded[0]) {
+                    case 0x42:
+                        printf("Temperature: ");
+                    break; case 0x50:
+                        printf("CO2:         ");
+                    break;
+                }
+            }
+
+            for (int i = 0; i < sizeof(buffer); i++) {
+                printf("[%i]: %X ", i, decoded[i]);
+            }
+
+            printf("\n");
+        }
+    }
+
+    close(device_handle);
+    return 0;
+}