My Venus GPS-09133 is a Rock

GPS/GNSS Development Boards
1

I am getting absolutely nothing out of my Venus GPS-09133.

The situation:

The SPI pins are all floating (unconnected).

I have 3.3V verified on the board pins 3V3 and VBAT, as well as across the filter cap on the board.

I left IO1, IO2, and IO20 floating.

There is an LED on the board that is glowing exceedingly dimly (barely visible). The board seems to be drawing very little power according to my power supply (maybe 10-20 mA).

I am using the TTL-level serial connection, set on my end to 9600 baud. The TX line from my UART is connected to the RX input on the board, and vice-versa.

I have tried sending the board commands, but I get no ACK or NAK. I get no output from the board either.

I see no activity on the device’s TX pin. Both TX and RX are always 3.3V.

Am I doing something obviously wrong here?

2

Found it. This might be of interest to others:

The Venus has a 1 pulse-per-second output signal. Apparently, if this signal is not floating when the Venus gets powered up, the entire venus chip hangs in the fashion that I described.

This odd behavior is a bit tricky when connecting to an ARM, since the reset default for an ARM is to enable GPIO pins as inputs (that’s OK), but with their port pullups enabled (apparently not OK for the Venus).

The only way I was able to make this work was to have the ARM disable its port pullup on the 1PPS signal as one of the very first instructions to be executed after reset. Any later than that, and the Venus would hang.