Has anyone taken a look at the ARTIK 030 module from Samsung? It's a Cortex-M4 based (SiLabs EFR32MG1 SoC) module with 256 kB flash and 32 kB SRAM, a cryto processor, and 802.15.4 radio.
In the US they're available from Digikey and Mouser for $7.30 in single unit quantities; I'm not sure who distributes them in the UK.
webpage: https://www.artik.io/modules/artik-030/ datasheet: https://developer.artik.io/downloads/1101cbd8-2ddf-404f-ac79-26488417c8cb/download
MCU Features
* ARM Cortex-M4 @ 40 MHz * Silicon Labs EFR32MG1 SoC * Low Active Mode Current: 63 μA/MHz * 256 kB flash, 32 kB SRAM * Hardware cryptography engine with support for AES-128/256, ECC, SHA-1, SHA-256, and a Random Number Generator * 8 Channel DMA Controller
Digital Peripherals
* 2 × USART (UART, SPI, IrDA, I²S) * Low Energy UART • I²C peripheral interface (address recognition down to EM3) * Timers: RTCC, Low Energy Timer, Pulse Counter * 12-channel Peripheral Reflex System (PRS) * Up to 25 GPIO with interrupts
Analog Peripherals
* ADC (12-bit, 1 Msps, 326 μA) * Current-mode Digital to Analog Converter (IDAC) * 2 × Analog Comparator (ACMP)
Low Power Modes
* Energy Mode 2 (Deep Sleep) Current: 2.5 μA (Full RAM retention and RTCC running from LXFO) * Ultra-fast wake up: 3 μS down to EM3 * Wide Supply Voltage range of 1.85 to 3.8 V Radio Features * 2.4 GHz with integrated balun * IEEE 802.15.4 * Data Rate / Modulation: 250 kbps DSSS-OQPSK * +10 dBm Programmable TX Power * -99 dBm RX Sensitivity * 9.8 mA RX current * 8.2 mA TX current (at +0 dBm) * Support for wireless mesh networking (ZigBee/Thread) * Integrated PA (up to +10 dBm TX power) * Packet Trace Interface (PTI) for non-intrusive packet trace with Simplicity Studio development tools * Antenna interface: integrated high-performance chip antennaor u.FL variant for external antenna
Misc. Features
* Support for SoC and Network Co-Processor (NCP) architectures with SPI/UART host support * Serial and Over-The-Air (OTA) bootloaders