diff --git a/ports/stm32/README.md b/ports/stm32/README.md
index bb184e8db6..cf539691c8 100644
--- a/ports/stm32/README.md
+++ b/ports/stm32/README.md
@@ -1,9 +1,9 @@
 MicroPython port to STM32 MCUs
 ==============================
 
-This directory contains the port of MicroPython to ST's line of STM32Fxxx
-microcontrollers.  It is based on the STM32Cube HAL library and currently
-supports: STM32F401, STM32F405, STM32F411, STM32F429, STM32F746.
+This directory contains the port of MicroPython to ST's line of STM32
+microcontrollers.  Supported MCU series are: STM32F4, STM32F7 and STM32L4.
+Parts of the code here utilise the STM32Cube HAL library.
 
 The officially supported boards are the line of pyboards: PYBv1.0 and PYBv1.1
 (both with STM32F405), and PYBLITEv1.0 (with STM32F411).  See
@@ -14,6 +14,12 @@ Other boards that are supported include ST Discovery and Nucleo boards.
 See the boards/ subdirectory, which contains the configuration files used
 to build each individual board.
 
+The STM32H7 series has preliminary support: there is a working REPL via
+USB and UART, as well as very basic peripheral support, but some things do
+not work and none of the advanced features of the STM32H7 are yet supported,
+such as the clock tree.  At this point the STM32H7 should be considered as a
+fast version of the STM32F7.
+
 Build instructions
 ------------------