You are not connecting to a proper ground point, that trace is the antenna. Second, the reason for the transistor circuit is that MFB is edge triggered. So when you connect your PSU (3.3V, Vbat) and MFB at the same time there is a chance the BT module misses the rising edge. The proper way of operation is using the transistor circuit and tie it to a 3.3V supply that starts up when the car starts up. If you only have a 3.3V supply that is always on, you could remove the transistor circuit and connect the MFB pin to some other 3.3V signal on the board that goes high when the system starts up.
Thanks for the reply! For testing purposes that antenna is a decent ground I'd say Hmmm, okay, but - so, you're saying that if there's no rising edge on the MFB, the chip doesn't turn on??? There also seems to be an internal pullup on that pin as well ... It seems kind of an odd requirement to need such attention to start the chip up
Is the antenna the same as ground? I thought it would be a seperate signal, but maybe its fine. I also dont know why they didnt just make it level triggered, this stuff only makes it more complicated. From the datasheet of the CSRA64215: "A rising edge on VREGENABLE (MFB) or VCHG is required to power on CSRA64215 QFN" I did a PCB design with the BTM625 where the 3.3V supply is always on and the MFB pin is controlled by a microcontroller. If you want your module to power on when the 3.3V is enabled, you need to use the delay circuit to ensure proper turn on.
You are not connecting to a proper ground point, that trace is the antenna. Second, the reason for the transistor circuit is that MFB is edge triggered. So when you connect your PSU (3.3V, Vbat) and MFB at the same time there is a chance the BT module misses the rising edge. The proper way of operation is using the transistor circuit and tie it to a 3.3V supply that starts up when the car starts up. If you only have a 3.3V supply that is always on, you could remove the transistor circuit and connect the MFB pin to some other 3.3V signal on the board that goes high when the system starts up.
Thanks for the reply! For testing purposes that antenna is a decent ground I'd say
Hmmm, okay, but - so, you're saying that if there's no rising edge on the MFB, the chip doesn't turn on???
There also seems to be an internal pullup on that pin as well ...
It seems kind of an odd requirement to need such attention to start the chip up
Also, if it's edge triggered, then it's RISING for turn-on and FALLING for sleep ... but ... is it really driven that way ?
Is the antenna the same as ground? I thought it would be a seperate signal, but maybe its fine. I also dont know why they didnt just make it level triggered, this stuff only makes it more complicated. From the datasheet of the CSRA64215: "A rising edge on VREGENABLE (MFB) or VCHG is required to power on CSRA64215 QFN"
I did a PCB design with the BTM625 where the 3.3V supply is always on and the MFB pin is controlled by a microcontroller. If you want your module to power on when the 3.3V is enabled, you need to use the delay circuit to ensure proper turn on.
Very interesting, thanks!
Yeah, antenna is ground, radio voodoo shit I know! But it does have many vias right to ground, have a closer look
I've commented on one of your videos