I have problem getting any feedback from Wismo 228 connected through UART.
My layout is similar to one found on Rocketscream Tralog and uses all design examples and recommendations in Wismo’s technical application guide. I would like to emphasize that this is prototype board, so no GSM antenna is connected and power is supplied directly from laboratory DC power supply (GW INSTEK GPS-3303).
For UART communication a MAX3232 is used as level shifter. UART is connected through UART to serial cable and PC is communicating via Terminal application. MAX 3232 is powered by 2,9 V and is sending data to WISMO TXD pin. WISMO is operating in 2 - wire configuration (no flow control)
When I connect power supply to WISMO (3,6V Nom voltage) I receive WISMO READY signal (logical high), but when I send AT commands to WISMO, nothing is returned in reply… . I tried lowering RTS and DTR to logical low (gnd) but WISMO hasn’t stopped giving me “silence treatment” - RXD is not sending anything. All signal nominations (TXD, RXD, DTR, RTS) are same as in Wismo Technical Guide
Thank you in advance for your quick reply