Using BlueSmirfs with UART pins

Wireless & IoT
1

Hi all-

I want to use the BlueSmirfs (only two I/O pins!), but also want to use the UART pins (Rx/Tx) on the same device.

If I put the BlueSmirf on the Tx/Rx pins, can I also upload stuff serially with a max232-type device, or is it recommended that I put the transceiver on different pins?

Thanks,

Jeff

2

Jeff,

Worry about bus contention. The MAX232 chip has a output pin and an input pin. It will try to drive the output pin (max232 TX to PIC rx) to whatever level it wants. If the BlueSMiRF is also attached to this line, the BlueSMiRF will also try controlling this line (BSM to PIC rx). Who wins? Not good.

The PIC tx to multiple devices is not too much of a problem as most devices will happily listen with high input impedences.

-Nathan

3

Nathan-

Thanks for responding; good point. If I totally eliminate the max232-type device (i.e. USB-to-RS232 chip or MAX232) and only use the bluesmrf, can i just use that for serial comms? … i.e. bootloading and communication? I wouldn’t have a hardware connection directly, but i’m fine with that if I can reliably use the blue guys for comms.

Thanks,

Jeff

4

Yes - getting rid of one or the other is ideal. We usually have two headers on all our proto designs. One for BlueSMiRF, one is a debug header that we can plug a shifter board on if we need a wired solution.

-Nathan