GM: change brake pressed signal (#1089)

* Match openpilot brake check

* comment

* simple

* Update test

* doesn't take an int

* msg varies in size by platform

* 2 extra bytes of zeros on Escalade

* label platforms

* space

board/safety/safety_gm.h

@@ -33,7 +33,9 @@ AddrCheckStruct gm_addr_checks[] = {
   {.msg = {{388, 0, 8, .expected_timestep = 100000U}, { 0 }, { 0 }}},
   {.msg = {{842, 0, 5, .expected_timestep = 100000U}, { 0 }, { 0 }}},
   {.msg = {{481, 0, 7, .expected_timestep = 100000U}, { 0 }, { 0 }}},
-  {.msg = {{241, 0, 6, .expected_timestep = 100000U}, { 0 }, { 0 }}},
+  {.msg = {{190, 0, 6, .expected_timestep = 100000U},    // Volt, Silverado, Acadia Denali
+           {190, 0, 7, .expected_timestep = 100000U},    // Bolt EUV
+           {190, 0, 8, .expected_timestep = 100000U}}},  // Escalade
   {.msg = {{452, 0, 8, .expected_timestep = 100000U}, { 0 }, { 0 }}},
 };
 #define GM_RX_CHECK_LEN (sizeof(gm_addr_checks) / sizeof(gm_addr_checks[0]))
@@ -89,10 +91,10 @@ static int gm_rx_hook(CANPacket_t *to_push) {
       cruise_button_prev = button;
     }
 
-    if (addr == 241) {
-      // Brake pedal's potentiometer returns near-zero reading
-      // even when pedal is not pressed
-      brake_pressed = GET_BYTE(to_push, 1) >= 10U;
+    if (addr == 190) {
+      // Reference for signal and threshold:
+      // https://github.com/commaai/openpilot/blob/master/selfdrive/car/gm/carstate.py
+      brake_pressed = GET_BYTE(to_push, 1) >= 8U;
     }
 
     if (addr == 452) {

tests/safety/test_gm.py

@@ -54,9 +54,9 @@ def _speed_msg(self, speed):
     return self.packer.make_can_msg_panda("EBCMWheelSpdRear", 0, values)
 
   def _user_brake_msg(self, brake):
-    # GM safety has a brake threshold of 10
-    values = {"BrakePedalPosition": 10 if brake else 0}
-    return self.packer.make_can_msg_panda("EBCMBrakePedalPosition", 0, values)
+    # GM safety has a brake threshold of 8
+    values = {"BrakePedalPos": 8 if brake else 0}
+    return self.packer.make_can_msg_panda("ECMAcceleratorPos", 0, values)
 
   def _user_regen_msg(self, regen):
     values = {"RegenPaddle": 2 if regen else 0}
@@ -109,7 +109,7 @@ def test_tx_hook_on_pedal_pressed(self):
       if pedal == 'brake':
         # brake_pressed_prev and vehicle_moving
         self._rx(self._speed_msg(100))
-        self._rx(self._user_brake_msg(MAX_BRAKE))
+        self._rx(self._user_brake_msg(1))
       elif pedal == 'gas':
         # gas_pressed_prev
         self._rx(self._user_gas_msg(MAX_GAS))
@@ -135,7 +135,7 @@ def test_tx_hook_on_pedal_pressed_on_alternative_gas_experience(self):
       if pedal == 'brake':
         # brake_pressed_prev and vehicle_moving
         self._rx(self._speed_msg(100))
-        self._rx(self._user_brake_msg(MAX_BRAKE))
+        self._rx(self._user_brake_msg(1))
         allow_ctrl = False
       elif pedal == 'gas':
         # gas_pressed_prev