On some of my boards, ALFAT-OEM 1.3 are not working but ALFAT-OEM 1.2 are working. When the ALFAT-OEM 1.3 isn’t working, I am often getting ? sent to me by the ALFAT at 500,000baud instead of an echo. I am using the UART interface.
Leave all pins of ALFAT unconnected, except for TX, RX, 3.3V, GND.
Make sure that the Reset to high, you can connect to 3.3.
Open any PC software that support serial port, TeraTerm is one of great application for this.
In PC, set up that application 115200, 8 bit, Parity None, stop bit 1.
Now you can send few commands from that app and ALFAT should responds.
Once you get successful with this step, then we can talk next thing, right now I don’t know where your status are.
No, no, no. At 500000 baud there aren’t several characters mashed together. It’s one ? character at 500000 baud. I verified this with a scope. This fact seems to be ignored. This really seems to imply that the unit is in some kind of weird mode, and I would have thought it would have been a clue to the developers as to what that mode was.
I just got the schematic (had to wait until after the holidays to hear back from the hardware designer). The RESET pin is connected to my MCU’s GPIO via a diode, so my MCU can ground the reset pin. I verified with a scope that it pulls it down. The only glitch is that the voltage doesn’t get pulldown to a full 0V, I will check the datasheet to see if there is a minimum voltage needed and if I’m not getting that low.
I AM NOT USING A DIFFERENT BAUD RATE. I am using 115200 and getting a ? response at 500000 baud.
On the boards that didn’t work there was something (pull-up or pull-down, can’t remember) on the BOOT pin. It’s there on the old boards because they were originally designed for the USBWIZ version of the OEM board. However, with error on the BOOT pin they still worked with ALFAT-OEM 1.2 and not ALFAT-OEM 1.3.
I’m guessing the ? at 500000 was due to the unit being in bootloader mode.
I’m surprised that in a forum full of GHI employees and experts they couldn’t point out to me what the changes were from ALFAT-OEM 1.2 to ALFAT-OEM 1.3 -AND- that the bootloader puts out ? at 500000 baud.