3 files changed, 54 insertions, 29 deletions

diff --git a/docs/feature_rgb_matrix.md b/docs/feature_rgb_matrix.md
index be763ee02..f3e25f2f1 100644
--- a/docs/feature_rgb_matrix.md
+++ b/docs/feature_rgb_matrix.md
@@ -145,9 +145,22 @@ There is basic support for addressable RGB matrix lighting with the I2C IS31FL37
 RGB_MATRIX_ENABLE = yes
 RGB_MATRIX_DRIVER = IS31FL3737
 ```
+You can use between 1 and 2 IS31FL3737 IC's. Do not specify `DRIVER_ADDR_2` define for second IC if not present on your keyboard.
 
 Configure the hardware via your `config.h`:
 
+| Variable | Description | Default |
+|----------|-------------|---------|
+| `ISSI_TIMEOUT` | (Optional) How long to wait for i2c messages, in milliseconds | 100 |
+| `ISSI_PERSISTENCE` | (Optional) Retry failed messages this many times | 0 |
+| `DRIVER_COUNT` | (Required) How many RGB driver IC's are present | |
+| `DRIVER_LED_TOTAL` | (Required) How many RGB lights are present across all drivers | |
+| `DRIVER_ADDR_1` | (Required) Address for the first RGB driver | |
+| `DRIVER_ADDR_2` | (Optional) Address for the second RGB driver | |
+
+
+Here is an example using 2 drivers.
+
 ```c
 // This is a 7-bit address, that gets left-shifted and bit 0
 // set to 0 for write, 1 for read (as per I2C protocol)
@@ -159,14 +172,16 @@ Configure the hardware via your `config.h`:
 // ADDR represents A3:A0 of the 7-bit address.
 // The result is: 0b101(ADDR)
 #define DRIVER_ADDR_1 0b1010000
-#define DRIVER_ADDR_2 0b1010000 // this is here for compliancy reasons.
+#define DRIVER_ADDR_2 0b1010001
 
 #define DRIVER_COUNT 2
-#define DRIVER_1_LED_TOTAL 64
-#define DRIVER_LED_TOTAL DRIVER_1_LED_TOTAL
+#define DRIVER_1_LED_TOTAL 30
+#define DRIVER_2_LED_TOTAL 36
+#define DRIVER_LED_TOTAL (DRIVER_1_LED_TOTAL + DRIVER_2_LED_TOTAL)
 ```
+!> Note the parentheses, this is so when `DRIVER_LED_TOTAL` is used in code and expanded, the values are added together before any additional math is applied to them. As an example, `rand() % (DRIVER_1_LED_TOTAL + DRIVER_2_LED_TOTAL)` will give very different results than `rand() % DRIVER_1_LED_TOTAL + DRIVER_2_LED_TOTAL`.
 
-Currently only a single drivers is supported, but it would be trivial to support all 4 combinations. For now define `DRIVER_ADDR_2` as `DRIVER_ADDR_1`
+Currently only 2 drivers are supported, but it would be trivial to support all 4 combinations. 
 
 Define these arrays listing all the LEDs in your `<keyboard>.c`:
 
@@ -183,7 +198,7 @@ const is31_led PROGMEM g_is31_leds[DRIVER_LED_TOTAL] = {
 }
 ```
 
-Where `X_Y` is the location of the LED in the matrix defined by [the datasheet](https://www.issi.com/WW/pdf/31FL3737.pdf) and the header file `drivers/issi/is31fl3737.h`. The `driver` is the index of the driver you defined in your `config.h` (Only `0` right now).
+Where `X_Y` is the location of the LED in the matrix defined by [the datasheet](https://www.issi.com/WW/pdf/31FL3737.pdf) and the header file `drivers/issi/is31fl3737.h`. The `driver` is the index of the driver you defined in your `config.h` (Only `0`, `1` for now).
 
 ---
 
diff --git a/drivers/issi/is31fl3737.c b/drivers/issi/is31fl3737.c
index e40bfa0d7..30906b484 100644
--- a/drivers/issi/is31fl3737.c
+++ b/drivers/issi/is31fl3737.c
@@ -66,11 +66,12 @@ uint8_t g_twi_transfer_buffer[20];
 // We could optimize this and take out the unused registers from these
 // buffers and the transfers in IS31FL3737_write_pwm_buffer() but it's
 // probably not worth the extra complexity.
+
 uint8_t g_pwm_buffer[DRIVER_COUNT][192];
-bool    g_pwm_buffer_update_required = false;
+bool    g_pwm_buffer_update_required[DRIVER_COUNT] = {false};
 
-uint8_t g_led_control_registers[DRIVER_COUNT][24] = {{0}};
-bool    g_led_control_registers_update_required   = false;
+uint8_t g_led_control_registers[DRIVER_COUNT][24]             = {0};
+bool    g_led_control_registers_update_required[DRIVER_COUNT] = {false};
 
 void IS31FL3737_write_register(uint8_t addr, uint8_t reg, uint8_t data) {
     g_twi_transfer_buffer[0] = reg;
@@ -158,10 +159,10 @@ void IS31FL3737_set_color(int index, uint8_t red, uint8_t green, uint8_t blue) {
         is31_led led;
         memcpy_P(&led, (&g_is31_leds[index]), sizeof(led));
 
-        g_pwm_buffer[led.driver][led.r] = red;
-        g_pwm_buffer[led.driver][led.g] = green;
-        g_pwm_buffer[led.driver][led.b] = blue;
-        g_pwm_buffer_update_required    = true;
+        g_pwm_buffer[led.driver][led.r]          = red;
+        g_pwm_buffer[led.driver][led.g]          = green;
+        g_pwm_buffer[led.driver][led.b]          = blue;
+        g_pwm_buffer_update_required[led.driver] = true;
     }
 }
 
@@ -199,30 +200,28 @@ void IS31FL3737_set_led_control_register(uint8_t index, bool red, bool green, bo
         g_led_control_registers[led.driver][control_register_b] &= ~(1 << bit_b);
     }
 
-    g_led_control_registers_update_required = true;
+    g_led_control_registers_update_required[led.driver] = true;
 }
 
-void IS31FL3737_update_pwm_buffers(uint8_t addr1, uint8_t addr2) {
-    if (g_pwm_buffer_update_required) {
+void IS31FL3737_update_pwm_buffers(uint8_t addr, uint8_t index) {
+    if (g_pwm_buffer_update_required[index]) {
         // Firstly we need to unlock the command register and select PG1
-        IS31FL3737_write_register(addr1, ISSI_COMMANDREGISTER_WRITELOCK, 0xC5);
-        IS31FL3737_write_register(addr1, ISSI_COMMANDREGISTER, ISSI_PAGE_PWM);
+        IS31FL3737_write_register(addr, ISSI_COMMANDREGISTER_WRITELOCK, 0xC5);
+        IS31FL3737_write_register(addr, ISSI_COMMANDREGISTER, ISSI_PAGE_PWM);
 
-        IS31FL3737_write_pwm_buffer(addr1, g_pwm_buffer[0]);
-        // IS31FL3737_write_pwm_buffer(addr2, g_pwm_buffer[1]);
+        IS31FL3737_write_pwm_buffer(addr, g_pwm_buffer[index]);
     }
-    g_pwm_buffer_update_required = false;
+    g_pwm_buffer_update_required[index] = false;
 }
 
-void IS31FL3737_update_led_control_registers(uint8_t addr1, uint8_t addr2) {
-    if (g_led_control_registers_update_required) {
+void IS31FL3737_update_led_control_registers(uint8_t addr, uint8_t index) {
+    if (g_led_control_registers_update_required[index]) {
         // Firstly we need to unlock the command register and select PG0
-        IS31FL3737_write_register(addr1, ISSI_COMMANDREGISTER_WRITELOCK, 0xC5);
-        IS31FL3737_write_register(addr1, ISSI_COMMANDREGISTER, ISSI_PAGE_LEDCONTROL);
+        IS31FL3737_write_register(addr, ISSI_COMMANDREGISTER_WRITELOCK, 0xC5);
+        IS31FL3737_write_register(addr, ISSI_COMMANDREGISTER, ISSI_PAGE_LEDCONTROL);
         for (int i = 0; i < 24; i++) {
-            IS31FL3737_write_register(addr1, i, g_led_control_registers[0][i]);
-            // IS31FL3737_write_register(addr2, i, g_led_control_registers[1][i]);
+            IS31FL3737_write_register(addr, i, g_led_control_registers[index][i]);
         }
-        g_led_control_registers_update_required = false;
     }
+    g_led_control_registers_update_required[index] = false;
 }
diff --git a/quantum/rgb_matrix/rgb_matrix_drivers.c b/quantum/rgb_matrix/rgb_matrix_drivers.c
index 6a11d4791..dfdf45219 100644
--- a/quantum/rgb_matrix/rgb_matrix_drivers.c
+++ b/quantum/rgb_matrix/rgb_matrix_drivers.c
@@ -65,6 +65,9 @@ static void init(void) {
 #        endif
 #    elif defined(IS31FL3737)
     IS31FL3737_init(DRIVER_ADDR_1);
+#        if defined(DRIVER_ADDR_2) && (DRIVER_ADDR_2 != DRIVER_ADDR_1)  // provides backward compatibility
+    IS31FL3737_init(DRIVER_ADDR_2);
+#        endif
 #    else
     IS31FL3741_init(DRIVER_ADDR_1);
 #    endif
@@ -105,7 +108,10 @@ static void init(void) {
     IS31FL3733_update_led_control_registers(DRIVER_ADDR_4, 3);
 #        endif
 #    elif defined(IS31FL3737)
-    IS31FL3737_update_led_control_registers(DRIVER_ADDR_1, DRIVER_ADDR_2);
+    IS31FL3737_update_led_control_registers(DRIVER_ADDR_1, 0);
+#        if defined(DRIVER_ADDR_2) && (DRIVER_ADDR_2 != DRIVER_ADDR_1)  // provides backward compatibility
+    IS31FL3737_update_led_control_registers(DRIVER_ADDR_2, 1);
+#        endif
 #    else
     IS31FL3741_update_led_control_registers(DRIVER_ADDR_1, 0);
 #    endif
@@ -152,7 +158,12 @@ const rgb_matrix_driver_t rgb_matrix_driver = {
     .set_color_all = IS31FL3733_set_color_all,
 };
 #    elif defined(IS31FL3737)
-static void flush(void) { IS31FL3737_update_pwm_buffers(DRIVER_ADDR_1, DRIVER_ADDR_2); }
+static void flush(void) {
+    IS31FL3737_update_pwm_buffers(DRIVER_ADDR_1, 0);
+#        if defined(DRIVER_ADDR_2) && (DRIVER_ADDR_2 != DRIVER_ADDR_1)  // provides backward compatibility
+    IS31FL3737_update_pwm_buffers(DRIVER_ADDR_2, 1);
+#        endif
+}
 
 const rgb_matrix_driver_t rgb_matrix_driver = {
     .init = init,