Support board "modbus_relay8"

[TG9541]

A MODBUS board with the name "modbus_relay8 v1.2" arrived a few days ago:

It has an STM8S103K3T6C, an LM2596-5V switching power supply (7..30V, 2-3A), 8 relays and 8 insulated inputs. The usual price is at $15.

I made a Gist with Forth code for I/O based on SWIMCOM. GPIOs for I/O are documented in the code.

Other GPIOs traced so far are:

GPIO	usage
PA1	Q (crystal not populated)
PA2	Q (crystal not populated)
PB6	S2 (key)
PB7	LED (not populated)
PD7	RS485 direction

[TG9541]

This works with the latest deferred BUSCTRL:

\ STM8EF-MODBUS eForth RS485 bus control for RS485 board RelayX8 

\res MCU: STM8S103
\res export PD_ODR PD_DDR PD_CR1

#require ]B!

NVM
  \ Set RS485 Driver to "RX"
  : rx ( -- )
    [ 0 PD_ODR 7 ]B!
  ;

  \ Set RS485 Driver to "TX"
  : tx ( -- )
    [ 1 PD_ODR 7 ]B!
  ;

  \ Initialize GPIO and RS485 Driver
  : CTRL ( -- )
    BUSrx
    [ 1 PD_DDR 7 ]B!
    [ 1 PD_CR1 7 ]B!
  ;

  ' rx is BUSrx
  ' tx is BUStx
  ' ctrl is BUSctrl
RAM