Here's my reply:Then one other question about a malfunctioning EB012. A customer wanted to connect the EB012 unit to his PDA, but discovered the on board MCP2150 failed to come in to a defined state after power up or after pressing the RESET button. He told us both LEDs seemed to light up randomly. Also, he tested optically (with a camera) if the IR LED blinked. It didn’t.
After some research he discovered that the MCP2150 manual <DS21655B.PDF> says that the DTR pin needs to be hardwired to Vss or Vcc. On the EB012 it isn’t connected at all. He solved his problems by connecting the DTR pin (pin 11) to GND of the DSR LED.
The way he explains, it seems to me this might be a small design flaw. Could you comment on this?
Thanks for the info regarding the IrDA board (EB012). Delving into the datasheet further, it seems that the initial state of both the RTS line and the DTR line are important. If RTS is low and DTR is high, then the MCP2150 will enter "Device ID programming mode".
Obviously in our hardware design, the state of DTR is undefined. If the initial state of the RTS line is also undefined (or set low), then the device could possibly enter this alternate mode and thus not behave appropriately.
I guess that every time we have used this in the past the state of RTS is set high, and this is why we have not seen this problem previously.
Anyway, it is a good spot by your customer - please pass on our thanks! And we will look into fixing it in a future revision of the board. We have also modified all of our existing stock, so this should not be a problem in the future.