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Add I2C support to STM32 platform
Signed-off-by: Paul Guyot <pguyot@kallisys.net>
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‎.github/workflows/stm32-build.yaml‎

Lines changed: 25 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -57,6 +57,11 @@ jobs:
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max_size: 393216
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renode_platform: stm32f4.repl
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avm_address: "0x08060000"
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# Renode's STM32F4_I2C model has a bug: it never calls
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# FinishTransmission() on the I2C slave when a STOP condition
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# occurs, causing the BME280 sensor to get stuck in Reading
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# state and ignore subsequent writes.
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skip_i2c_test: true
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- device: stm32h743vit6
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max_size: 524288
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renode_platform: stm32h743.repl
@@ -79,6 +84,10 @@ jobs:
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max_size: 393216
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renode_platform: stm32l562.repl
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avm_address: "0x08060000"
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# Renode's built-in stm32l552.repl uses STM32F4_I2C (legacy I2C
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# register layout) but the L5 HAL uses the newer I2C registers
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# (TIMINGR, ISR, etc.), causing a complete register mismatch.
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skip_i2c_test: true
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- device: stm32f207zgt6
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max_size: 524288
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- device: stm32u375rgt6
@@ -149,7 +158,7 @@ jobs:
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mkdir build-host
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cd build-host
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cmake .. -G Ninja
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cmake --build . -t stm32_boot_test stm32_gpio_test
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cmake --build . -t stm32_boot_test stm32_gpio_test stm32_i2c_test
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- name: Install Renode
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if: matrix.renode_platform
@@ -190,3 +199,18 @@ jobs:
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--variable AVM:@$PWD/build-host/src/platforms/stm32/tests/test_erl_sources/stm32_gpio_test.avm \
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--variable AVM_ADDRESS:${{ matrix.avm_address }} \
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--variable PLATFORM:$PLATFORM
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- name: Run Renode I2C test
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if: matrix.renode_platform && !matrix.skip_i2c_test
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run: |
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LOCAL_REPL="src/platforms/stm32/tests/renode/${{ matrix.renode_platform }}"
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if [ -f "$LOCAL_REPL" ]; then
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PLATFORM="@$PWD/$LOCAL_REPL"
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else
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PLATFORM="@platforms/cpus/${{ matrix.renode_platform }}"
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fi
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renode-test src/platforms/stm32/tests/renode/stm32_i2c_test.robot \
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--variable ELF:@$PWD/src/platforms/stm32/build/AtomVM-${{ matrix.device }}.elf \
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--variable AVM:@$PWD/build-host/src/platforms/stm32/tests/test_erl_sources/stm32_i2c_test.avm \
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--variable AVM_ADDRESS:${{ matrix.avm_address }} \
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--variable PLATFORM:$PLATFORM

‎examples/erlang/stm32/CMakeLists.txt‎

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Original file line numberDiff line numberDiff line change
@@ -27,3 +27,4 @@ pack_runnable(blink_weact_studio_h562 blink_weact_studio_h562 eavmlib avm_stm32)
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pack_runnable(blink_weact_studio_h743 blink_weact_studio_h743 eavmlib avm_stm32)
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pack_runnable(blink_weact_studio_u585 blink_weact_studio_u585 eavmlib avm_stm32)
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pack_runnable(blink_weact_studio_wb55 blink_weact_studio_wb55 eavmlib avm_stm32)
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pack_runnable(stm32_lis3dh stm32_lis3dh eavmlib avm_stm32)

‎examples/erlang/stm32/stm32_lis3dh.erl‎

Lines changed: 122 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,122 @@
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%
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% This file is part of AtomVM.
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%
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% Copyright 2026 Paul Guyot <pguyot@kallisys.net>
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%
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% Licensed under the Apache License, Version 2.0 (the "License");
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% you may not use this file except in compliance with the License.
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% You may obtain a copy of the License at
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%
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% http://www.apache.org/licenses/LICENSE-2.0
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%
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% Unless required by applicable law or agreed to in writing, software
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% distributed under the License is distributed on an "AS IS" BASIS,
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% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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% See the License for the specific language governing permissions and
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% limitations under the License.
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%
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% SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later
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%
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%%-----------------------------------------------------------------------------
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%% @doc LIS3DH accelerometer example for STM32.
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%%
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%% Reads X, Y, Z acceleration from a LIS3DH connected via I2C and prints
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%% the values every second.
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%%
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%% Default wiring (I2C1 on most STM32 boards):
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%% SCL -> PB6
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%% SDA -> PB7
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%%
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%% The alternate function number defaults to 4, which is correct for I2C1
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%% on most STM32 families. Adjust `af' if your chip uses a different mapping.
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%% @end
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%%-----------------------------------------------------------------------------
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-module(stm32_lis3dh).
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-export([start/0]).
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%% I2C1 pins (PB6/PB7 are common I2C1 pins across STM32 families)
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-define(SCL_PIN, {b, 6}).
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-define(SDA_PIN, {b, 7}).
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%% LIS3DH I2C address (0x18 when SDO/SA0 is low, 0x19 when high)
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-define(LIS3DH_ADDR, 16#19).
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%% LIS3DH registers
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-define(WHO_AM_I, 16#0F).
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-define(CTRL_REG1, 16#20).
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-define(CTRL_REG4, 16#23).
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-define(OUT_X_L, 16#28).
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%% Expected WHO_AM_I response
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-define(LIS3DH_ID, 16#33).
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start() ->
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I2C = i2c:open([
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{scl, ?SCL_PIN},
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{sda, ?SDA_PIN},
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{clock_speed_hz, 400000},
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{peripheral, 1}
60+
]),
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case check_who_am_i(I2C) of
62+
ok ->
63+
configure(I2C),
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loop(I2C);
65+
{error, Reason} ->
66+
console:puts("LIS3DH not found: "),
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console:puts(erlang:atom_to_list(Reason)),
68+
console:puts("\n")
69+
end.
70+
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check_who_am_i(I2C) ->
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case i2c:read_bytes(I2C, ?LIS3DH_ADDR, ?WHO_AM_I, 1) of
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{ok, <<?LIS3DH_ID:8>>} ->
74+
console:puts("LIS3DH detected\n"),
75+
ok;
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{ok, <<Other:8>>} ->
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console:puts("Unexpected WHO_AM_I: "),
78+
console:puts(erlang:integer_to_list(Other, 16)),
79+
console:puts("\n"),
80+
{error, unexpected_id};
81+
{error, _} = Error ->
82+
Error
83+
end.
84+
85+
configure(I2C) ->
86+
%% CTRL_REG1: 50 Hz ODR, normal mode, X/Y/Z enabled
87+
%% Bits: ODR=0100 LPen=0 Zen=1 Yen=1 Xen=1 -> 0x47
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ok = i2c:write_bytes(I2C, ?LIS3DH_ADDR, ?CTRL_REG1, 16#47),
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%% CTRL_REG4: +/- 2g full scale, high resolution
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%% Bits: BDU=1 BLE=0 FS=00 HR=1 ST=00 SIM=0 -> 0x88
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ok = i2c:write_bytes(I2C, ?LIS3DH_ADDR, ?CTRL_REG4, 16#88).
92+
93+
loop(I2C) ->
94+
case read_acceleration(I2C) of
95+
{ok, {X, Y, Z}} ->
96+
console:puts("X="),
97+
console:puts(erlang:integer_to_list(X)),
98+
console:puts(" Y="),
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console:puts(erlang:integer_to_list(Y)),
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console:puts(" Z="),
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console:puts(erlang:integer_to_list(Z)),
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console:puts("\n");
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{error, Reason} ->
104+
console:puts("Read error: "),
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console:puts(erlang:atom_to_list(Reason)),
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console:puts("\n")
107+
end,
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timer:sleep(1000),
109+
loop(I2C).
110+
111+
read_acceleration(I2C) ->
112+
%% Read 6 bytes starting at OUT_X_L with auto-increment (bit 7 set)
113+
case i2c:read_bytes(I2C, ?LIS3DH_ADDR, ?OUT_X_L bor 16#80, 6) of
114+
{ok, <<XL:8, XH:8/signed, YL:8, YH:8/signed, ZL:8, ZH:8/signed>>} ->
115+
%% 12-bit left-justified in high-resolution mode: shift right by 4
116+
X = ((XH bsl 8) bor XL) bsr 4,
117+
Y = ((YH bsl 8) bor YL) bsr 4,
118+
Z = ((ZH bsl 8) bor ZL) bsr 4,
119+
{ok, {X, Y, Z}};
120+
{error, _} = Error ->
121+
Error
122+
end.

‎libs/avm_stm32/src/CMakeLists.txt‎

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Original file line numberDiff line numberDiff line change
@@ -24,6 +24,7 @@ include(BuildErlang)
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set(ERLANG_MODULES
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gpio
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i2c
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)
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pack_archive(avm_stm32 DEPENDS_ON eavmlib ERLC_FLAGS +warnings_as_errors MODULES ${ERLANG_MODULES})

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