# HG changeset patch # User Mychaela Falconia # Date 1559938849 0 # Node ID c06cac606af33a5605a01da3da45d26fbbeecbdc # Parent d6b65114b82df03e193dd7f70ab499cdd982c886 gtm900/interface-signals: notes from connection tracing diff -r d6b65114b82d -r c06cac606af3 gtm900/interface-signals --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/gtm900/interface-signals Fri Jun 07 20:20:49 2019 +0000 @@ -0,0 +1,49 @@ +UART interfaces +=============== + +Both Calypso UARTs are brought out on the GTM900 module interface as follows: + +Pin Name in manual Connected Calypso ball +11 RXD2 TX_IRDA +12 TXD2 RX_IRDA +------------------------------- +16 UART_DSR GPIO1 +17 UART_RI GPIO0 +18 UART_RXD TX_MODEM +19 UART_TXD RX_MODEM +20 UART_CTS RTS_MODEM +21 UART_RTS CTS_MODEM +22 UART_DTR GPIO3 +23 UART_DCD GPIO2 + +The interface signal names in Huawei's manual are given from the host's +perspective (classic DTE-to-DCE paradigm), thus they are the opposite of the +connected Calypso signal names. For the MODEM UART a complete 8-signal +interface with full modem control is defined, but the Calypso only provides +TxD & RxD, RTS & CTS, thus the other 4 modem control signals are GPIOs. The +signals which are defined as DTR and DCD from the host's perspective are +connected to GPIOs 3 and 2, respectively, just like on TI's C-Sample and +D-Sample boards, whereas the choices of GPIOs for DSR and RI are Huawei's own +arbitrary picks, as TI's development boards did not provide these signals. + +Power control signals +===================== + +Interface pin 13 (called VDD in the manual) appears to be connected to the V-IO +rail inside. + +Interface pin 15 (PWON) is connected directly to Iota PWON as expected. + +Interface pin 31 (called RST in the manual) appears to be connected to Iota +nTESTRESET through the same transistor circuit as on TI's development boards, +i.e., the signal brought out on the module interface is not raw nTESTRESET, but +what we call XDS_RESET, originally meant to be driven by TI's XDS510 and XDS560 +"emulator" pods. + +Other signals +============= + +Interface pin 14 (called ADC in the manual) is connected to Iota ADIN1. + +Interface pin 32 (called LPG in the manual) is indeed connected to Calypso ball +DSR_MODEM/LPG, which Huawei's firmware configures to be the LPG output.