"Ghetto radio" solutions

[jonas-schievink]

The nRF51 board I'm using is already very affordable and there's not much wrong with it, but for experimentation I want to see if it's possible to implement everything except the bare radio in software. To do that, we need a radio chip that can do the following:

• Packet buffer size of at least 47 Bytes (max. Link-Layer packet size)
• GFSK modulation in the 2.4 GHz band
  • BT=0.5
  • Modulation index 0.45-0.55
• "BTLE needs us to be able to hop quickly - 150us or faster."

If a device like this can be made to work with a normal PC it would simplify development quite a bit, since we could use less restricted debugging and logging methods, so I'm also looking for comparable devices with USB support. Of course, it's also possible to hook a radio to an MCU with USB support and hook that up to a PC (possibly even implementing Linux' Software-defined radio interface and then implementing Transmitter for all SDRs that support the requirements).

Contenders:

• nRF24L01+
  • Lots of cheap breakouts available
  • Speaks SPI
  • Only seems to have 32 Byte FIFOs
  • See https://dmitry.gr/index.php?r=05.Projects&proj=11.%20Bluetooth%20LE%20fakery
• CC2500
  • Also has lots of cheap breakouts available
  • https://github.com/mcauser/CC2500-Breakout
  • https://www.aliexpress.com/item/2-4G-wireless-module-24TRGC2-wireless-module-GC-02-module/32817296334.html
  • Also speaks SPI
  • FIFO size of 64 Bytes
  • Unfortunately, this claims that it's not modulation-compatible with BLE - which seems odd, given that it supports GFSK with configurable deviation?
  • Update: The difference here is that the CC2500 uses a gaussian filter with BT=1, while BLE mandates BT=0.5
• A7125
  • Claims FSK support, but no GFSK (it could possibly still work I think?)
  • SPI
  • 64 Byte FIFOs
• ???

[jonas-schievink]

Closing since this is not really relevant to rubble anymore.