Update README to link to crates.io

README.md

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 # `tm4c129x-hal` and `tm4c123x-hal`
 
-> An [Embedded HAL] for the [TM4C129x] and [TM4C123x] families of microcontrollers from Texas Instruments.
+> An [Embedded HAL] (Hardware Abstraction Layer) for the [TM4C129x] and [TM4C123x] families of microcontrollers from Texas Instruments.
 
 [Embedded HAL]: https://crates.io/crates/embedded-hal
 [TM4C123x]: https://www.ti.com/product/TM4C123GH6PM
 [TM4C129x]: https://www.ti.com/product/TM4C1294NCPDT
 
+These microcontrollers are based on the Arm Cortex-M4F processor core and derived from the earlier TI/Luminary Micro LM4 and LM3 series MCUs. This HAL may work on an LM4F series MCU, but there are no guarantees. A full list of TM4C series microcontrollers is available from TI in [Document SPMT285D](https://www.ti.com/lit/sg/spmt285d/spmt285d.pdf).
+
+## Crates
+
+This repo comprises:
+
+* `tm4c123x-hal` [![tm4c123x-hal version](https://img.shields.io/crates/v/tm4c123x-hal.svg)](https://crates.io/crates/tm4c123x-hal/) - a HAL for the TM4C123GH6PM and related microcontrollers
+* `tm4c129x-hal` [![tm4c129x-hal version](https://img.shields.io/crates/v/tm4c129x-hal.svg)](https://crates.io/crates/tm4c129x-hal/) - a HAL for the TM4C1294NCPDT and related microcontrollers
+* `tm4c-hal` [![tm4c-hal version](https://img.shields.io/crates/v/tm4c-hal.svg)](https://crates.io/crates/tm4c-hal/) - drivers and HAL implementation that is common to both the above MCU families
+
 ## Example Hardware
 
 These crates are tested on the following Tiva-C Launchpad boards: