Our cellular radio module works great, but while in the process of trying to design a board around it, I noticed that the schematics apparently have TXD wired to the Gadgeteer Tx pin, and RXD wired to the Gadgeteer Rx pin. According to the Gadgeteer docs, Gadgeteer Tx is data coming from the mainboard, to the module. From reading the SIM900 documentation, TXD is data sent from the SIM900 module, and RXD is data sent to the module.
Shouldn’t TXD be wired to Gadgeteer Rx, and RXD wired to Gadgeteer Tx? Which documentation is wrong? The Cellular Radio schematics? Or the SIM900 manual?