July 18, 2019

GPIO port for Raspberry Pi

As part of the R&D work on port! datatype in port-type branch, we have implemented a GPIO driver for Raspberry Pi boards, as a gpio:// scheme (no third-party library needed). This work helped define the low-level API for ports written in purely Red/System or a mix of Red and Red/System.

The Raspberry Pi is a very popular board with millions of units sold, so this is a market where Red could be potentially helpful to developers. We could run Red on such boards for years but did not have proper GPIO support, so this is now fixed!

The current features supported by the GPIO port are:
  • auto-detecting the Raspberry Pi board type
  • uses /dev/mem or/dev/gpiomem for direct and fast access.
  • reading a GPIO pin state.
  • writing to a GPIO pin state.
  • hardware PWM output support (on capable pins).
  • a simple DSL for sending commands.

Planned (but not scheduled) future features include:
  • generating events when a pin state changes.
  • software PWM on all GPIO pins.
  • a higher-level reactive object layer for a API-less interface.
  • various drivers for common peripherals.

The source code for the gpio:// scheme can be found there.

In the short video below, you can find a little pet project meant for testing some of the features. It implements a simple joypad with 4 directions support, a red LED indicating when the pad is active and a green one for notifying when a level is completed. The game is the Red port contributed by Huang Yongzhao of Rebox!, my old clone of BoxWorld written in Rebol. In the video below, it is running on a Raspberry Pi 3 using our work-in-progress red/GTK backend for Red (contributed by Rcqls), locally merged with the red/port-type development branch (EDIT: that branch has been merged into master now).

You can find the breadboard layout below made using Fritzing. Sorry for the messy wiring, it is my first try with such kind of tool. If you have the skills to improve it, here is the sketch file. The buttons rely on the internal pull-down resistors. Note that in the video, the board is reversed.

The source code of Redbox has been modified to add GPIO support, you can find the modified code here. The GPIO-related code is enclosed in a context:

    joypad: context [
        mapping: [
            16 down  20 up
            17 left  21 right

        row: [(id) state: #[false] direction: (direction)]
        table: collect [
            foreach [id direction] mapping [keep compose row]

        pins: extract table length? row
        port: none

        acquire: has [pin][
            port: open gpio://
            foreach pin pins [
                insert port [
                    set-mode  pin in
                    pull-down pin

            insert port [
                set-mode 18 out
                set-mode  4 out
                set 4 on

        pressed?: function [][
            foreach pin pins [
                entry: find table pin
                old: entry/state

                insert port [get pin]
                entry/state: make logic! port/data

                ;-- detect 0-to-1 transitions only, to avoid auto-firing
                if all [not old entry/state][return entry/direction]

        show-win: does [insert port [set 18 on]]

        release: does [
            insert port [
                set  4 off
                set 18 off
            close port

The GPIO port has a simple API:

  • opening: port: open gpio://
  • sending commands: insert port [...commands...]
  • closing: close port

The sent commands form a small DSL:
Set the working mode for a given pin:
    set-mode <pin> <mode>

    <pin> : pin number (integer!)
    <mode>: in, out, pwm

Write a value on a pin: 
    set <pin> <value>
    <pin>  : pin number (integer!)
    <value>: true, false, on, off, yes, no, 0, 1

Read a value from a pin (the returned value is in port/data):

    get <pin>

    <pin>: pin number (integer!)    

Manage pull-up/down resistors:

   pull-off <pin>    ;-- disable any pull previously set
   pull-down <pin>   ;-- activate pull-down on the given pin
   pull-up <pin>     ;-- activate pull-up on the given pin   

Write a PWM value on a pin:

   set-pwm <pin> <value>
   <pin>  : pin number (integer!)
   <value>: an integer between 0 and 1024, or a percentage for duty cycle.

Fade in/out values on a PWM pin:

   fade <pin> from <start> to <end> <delay>   

   <pin>  : pin number (integer!)
   <start>: starting value (0-1024)
   <end>  : ending value (0-1024)
   <delay>: duration of the whole fading (time!)

Wait for a given duration:

   pause <delay>

   <delay>: integer => pause in miliseconds, float => pause in seconds.

Important notes
  • Only BCM numbering for GPIO pins is supported.
  • A word, or path or paren expression containing regular Red code can be used in place of any numeric value.
  • A single command block can contain an arbitrary number of commands.
  • The get command can be used multiple times, a block of corresponding results will then be returned in port/data.
  • Use sudo when running your GPIO code if it involves PWM!
  • An example of using fade and other commands is available here.
  • The PWM range is currently preset to 1024, though, the DSL can be trivially extended to allow a user-provided range value.

Happy hardware hacking! ;-)

July 9, 2019

RED Wallet 0.4.0

We are releasing today the version 0.4.0 of the RED Wallet with several major new features. As a reminder, the RED Wallet aims to be a simple and very secure wallet for the major cryptocurrencies (BTC, ETH, and ERC-20 tokens). Safety is enforced through the mandatory use of a hardware key (Ledger or Trezor keys), which protects against any failure of the wallet app (being it a bug or an attacker). The RED Wallet code is fully written in Red (using the Red/System DSL for USB drivers implementation) and open source.

BTC support

The RED Wallet now supports the bitcoin network. The main features are:
  • retrieval of address balances.
  • sending transactions (with follow-up on an online block explorer).
  • support both SegWit and Legacy addresses.
  • support both mainnet and testnet.

The balance retrieval can be quite slow on the bitcoin network, so be patient.

ERC-20 tokens support

ERC-20 tokens are supported since version 0.3.0. Though, Ledger removed the ERC-20 tokens list from the embedded Ethereum app since version 1.2.6, leaving it to the wallet app to manage the tokens list. This release now incorporates that list in the RED Wallet binary directly, resulting in a significantly bigger binary (about 100 KB bigger than 0.3.0). The Nano keys will still check the validity of the tokens addresses internally for extra safety. Another consequence of Ledger's recent firmware updates is noticeably slower addresses retrieval when plugging the key. That's an internal change in the Ledger key, so we cannot do anything to bring back the fast speed we could achieve with older firmware.

As a reminder, BIP44 address derivation support is present in the wallet since 0.3.0. If you are using a key initialized in an older Ledger Live version, the derivation path would be different and in order to make the wallet recognize your key, you need to click on the "(Legacy)" label (we will improve that UI in further versions).

Batch transactions were introduced in 0.2.0, they now work for any ERC-20 tokens in addition to ETH. They can be accessed from a contextual menu using a right click on an ETH account.


The RED Wallet has updated the firmware support:

  • Wallet v0.3.0: Compatibility with firmware 1.7.1+
  • Wallet v0.4.0: Support for the latest firmware of the Trezor key. 1.8

TREZOR model T is fully supported on macOS. On Windows 7, if the key is not recognized, you need to install the TREZOR bridge first.

Bug fixes

  • FIX: Ledger key does not work on Windows in some cases.
  • FIX: crashes in some cases when using Ledger key on Windows.
  • FIX: only ledger key is usable when plugging both ledger key and trezor key.
  • FIX: trezor-driver context name is wrong.

Download the RED Wallet 0.4.0

Just click on the executable to run it (extract the .app file first on macOS), no installation or setup process required. Plug in your Ledger or TREZOR key and enjoy a smooth and simple experience!

If you want to check if your RED Wallet binary has been tampered with in any way, you can simply drag'n drop the wallet executable on our binary checking service. If it's legit, the screen will turn green. If it turns red with a warning message, please notify us on Gitter or Twitter at once.

Only download the RED Wallet app from this page, do not trust any other website for that.


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