HydraFW GPIO guide

HydraFW GPIO (General Purpose Input/Output)

This guide is updated towards firmware release HydraFW v0.9 Beta and later

Input type:  0 to 5V

Output type: 3.3volt normal, or open drain
(pull up/pull down resistors integrated in MCU or external).
Pull-up/down resistors Integrated in MCU: Between 30 to 50K (Typical 40K).
Maximum voltage: 5.5volts (5volt safe).

Output type - open drain/open collector (high=Hi-Z, low=ground),
 normal (high=3.3volts, low=ground).
Use open drain/open collector output types with pull-up resistors
for multi-voltage interfacing.

GPIO configuration syntax description:

Configuration: gpio <"PA0-15", "PB0-11", "PC0-15", "PA*"> <mode (in/out/open-drain)> [pull (up/down/floating)]

Interaction: gpio <"PA0-15", "PB0-11", "PC0-15", "PA*"> [period (nb ms)] <read/continuous> or <on/off>

Syntax:

• <string> One or more GPIO pins "PA0-15", "PB0-11", "PC0-15", "PA*"

• mode with parameter in, out or open-drain

• pull with parameter up or down or floating to choose internal MCU pull up/down or no pull/external

• read read GPIO value(s)

• continuous read continuously

• on Set GPIO pin (work only for GPIO configured as out or open-drain)

• off Clear GPIO pin (work only for GPIO configured as out or open-drain)

GPIO configuration & interaction example:

Configuration & interaction on HydraNFC GPIO:

Since HydraFW v0.9 Beta commit 19c2fbd it is possible to skip the spaces between tokens we also call that Compressed mode but it is also mandatory to add quotes for each <string> so now it is mandatory to add quotes like that:

> gpio "pa3" "pb11" mode out off
Clearing PA3 PB11

> gpio "pa2" "pc0-1" mode out on
Setting PA2 PC0 PC1

> gpio "pb11" mode out on
Setting PB11

> gpio "pa2-3" "pc0-1" "pb11" r
PA2     1
PA3     0
PB11    1
PC0     1
PC1     1

Warning with PA9 in open-drain with internal pull up on

> gpio "pa9" mode open-drain pull up on
If we measure the PA9 we should think it output +3v3 but in fact the output is +1.1V
It seems linked to the fact this pin is special like defined in datasheet https://www.st.com/resource/en/datasheet/stm32f415rg.pdf 
see Table 58. USB OTG FS DC electrical characteristics => it seems linked to RPD / RPU for PA9 to be confirmed