Why I Use the CC2500 in My Projects

CC2500 RF transceiver module

The CC2500 is a 2.4 GHz transceiver by Texas Instruments. I mostly use it as a receiver for my prototypes. I work with different frequency bands in my hardware experiments, but the 2.4 GHz band is particularly convenient for fast prototyping — unlicensed ISM band, compact antennas, and stable modules. The CC2500 chip fits this workflow perfectly thanks to its flexibility and direct register control.

Key Specs (from the Datasheet)

CC2500 block diagram (datasheet image)

CC2500 vs nRF24L01

Comparison of 2.4 GHz transceivers
Feature CC2500 nRF24L01
Type2.4 GHz transceiver (multi-modulation)2.4 GHz transceiver (packet-based)
Modulation2-FSK / GFSK / MSK / OOKGFSK only
RSSI readoutYes (real-time RSSI per channel)No (not exposed)
Channel scanningEasy sweeping & logging RSSILimited to active link channels
Integration levelLow-level & flexibleHigh-level link-focused
Best useSpectrum experiments, analysisSimple MCU-to-MCU links

I use the CC2500 mainly because it exposes a reliable RSSI register. That enables simple spectrum analyzers, real-time signal visualization, and channel activity detection — something the nRF24L01 cannot do. For prototyping and testing, that single feature is decisive.

Setup Frequency

The CC2500 determines its actual RF output or reception frequency as: 

fRF = fbase + CHANNR × CHANSPC

In other words, the total frequency is built from three components:

So, for every channel the CC2500 tunes to: 

f_RF = (FREQ × f_XOSC / 2¹⁶) + CHANNR × (f_XOSC / 2¹⁸ × (256 + MDMCFG0) × 2MDMCFG1[1:0])

These parameters together fully define the synthesizer configuration. Adjusting FREQ2:0 changes the entire frequency band; CHANNR moves across channels within that band; MDMCFG1:0 controls how far apart those channels are.

#ifndef MDMCFG0 #define MDMCFG0 0x14 #define MDMCFG1 0x13 #define FREQ2 0x0D #define FREQ1 0x0E #define FREQ0 0x0F #define CHANNR 0x0A #endif static const double FXOSC = 26e6; // 26 MHz crystal // Channel spacing (CHANSPC) in Hz double cc2500_getChanSpc_Hz() { uint8_t mdmcfg1 = cc2500_readReg(MDMCFG1); uint8_t mdmcfg0 = cc2500_readReg(MDMCFG0); uint8_t CHANSPC_E = mdmcfg1 & 0x03; // [1:0] uint8_t CHANSPC_M = mdmcfg0; // [7:0] // TI: CHANSPC = fXOSC / 2^18 * (256 + M) * 2^E double base = FXOSC / 262144.0; // 2^18 return base * (256.0 + CHANSPC_M) * (1 << CHANSPC_E); } // Actual RF (with CHANNR), in Hz double cc2500_getRF_Hz() { uint8_t f2 = cc2500_readReg(FREQ2); uint8_t f1 = cc2500_readReg(FREQ1); uint8_t f0 = cc2500_readReg(FREQ0); uint32_t FREQ = ((uint32_t)f2 << 16) | ((uint32_t)f1 << 8) | f0; double f_base = (double)FREQ * FXOSC / 65536.0; uint8_t ch = cc2500_readReg(CHANNR); double chspc = cc2500_getChanSpc_Hz(); return f_base + ch * chspc; } void cc2500_printWhereWeAre() { double chspc = cc2500_getChanSpc_Hz(); double rf = cc2500_getRF_Hz(); uint8_t ch = cc2500_readReg(CHANNR); uint8_t f2 = cc2500_readReg(FREQ2), f1 = cc2500_readReg(FREQ1), f0 = cc2500_readReg(FREQ0); Serial.print(F("FREQ2:0 = ")); Serial.print(f2,HEX); Serial.print(' '); Serial.print(f1,HEX); Serial.print(' '); Serial.println(f0,HEX); Serial.print(F("CHANNR = ")); Serial.println(ch); Serial.print(F("CHANSPC ≈ ")); Serial.print(chspc/1e3,1); Serial.println(F(" kHz")); Serial.print(F("RF ≈ ")); Serial.print(rf/1e6,3); Serial.println(F(" MHz")); }

Tip: in a sweep, program FREQ2:0, MDMCFG1:0, CHANNR, do SCAL (or enable MCSM0.FS_AUTOCAL), enter RX, read RSSI, then move to the next channel.

How the Real Prototype Works

CC2500-based prototype photo
My custom CC2500 board: SMA connector, 26 MHz crystal, and matching network for 2.4 GHz.
Scrolling spectrogram GIF from the prototype
Live RSSI sweep from CC2500

Prototype overview: