Good evening all. I've managed to build a 4Pro transmitter PCB which basically works. I can't say soldering SMD devices is easy, but with a headband magnifier and a good work vice it is manageable. Just be careful not to sneeze or the components will disappear 
However there seems to be a problem with the I2C bus. On startup, the transmit LED only flashes 5 times then hangs. Looking at the serial monitor it fails to read or send the temperature/humidity data (SHT31). If I disable the T0 and T1 options in config options the system continues sending all the other data, and the test i2c detect sketch does not find any devices. If I fit the same arduino nano to an old Pro 2 Tx board with the same SHT31 it works perfectly, even with just the USB input as power.
On the 4Pro board the SCLOCK bus is high at 5v but the SDAT is only around 3 volts. Looking at the schematic, I would expect SDAT to be normally high 5V. I've checked the 4K7 pullup R6 and it is correct. Could the problem be one or more faulty I2C bus extender chips (IC3/4)perhaps? It's obviously not a dead short. Any other ideas before I start trying to isolate the SDA input pins on the bus extenders? Thank you.
Devon Sun
However there seems to be a problem with the I2C bus. On startup, the transmit LED only flashes 5 times then hangs. Looking at the serial monitor it fails to read or send the temperature/humidity data (SHT31). If I disable the T0 and T1 options in config options the system continues sending all the other data, and the test i2c detect sketch does not find any devices. If I fit the same arduino nano to an old Pro 2 Tx board with the same SHT31 it works perfectly, even with just the USB input as power.
On the 4Pro board the SCLOCK bus is high at 5v but the SDAT is only around 3 volts. Looking at the schematic, I would expect SDAT to be normally high 5V. I've checked the 4K7 pullup R6 and it is correct. Could the problem be one or more faulty I2C bus extender chips (IC3/4)perhaps? It's obviously not a dead short. Any other ideas before I start trying to isolate the SDA input pins on the bus extenders? Thank you.
Devon Sun
