RDA microelectronics RDA58xx family

Quite similar to the Si4700 chips (even the same I2C? address), but with a different register map.

This chip is used in some Sansa Clip+ players. It is made by RDA Microelectronics and is remarkably similar to the Si4700, but with a different register layout.

This chip appears to have 32 registers of 16-bit each. Writes start at register 0x02, read start at register 0x0A (similar to si4700). The first 16 registers are shown below.

Radio chip detection

• Radio chip detection: Read 128 bytes from the chip, check if bytes[4] == 0x58. If this is the case, the chip has been detected. Now write 2 bytes (0x200) and wait a bit (10 ms), then check bytes[6] and compare against 0. If 0, write a set of 72 initialisation values, else write a set of 82 initialisation values.
• Mute radio: Set or clear the DMUTE bit, just like the si4700. Also set bits 9 and 10 of register 0x04 and the four lowest bits of register 5 (VOLUME).
• Force mono: Set or clear the MONO bit, just like the si4700.
• Set band: Write the 2-bit band code in BAND, similar to the si4700, but in a different location.The lowest bit of BAND indicates the start of the band as follows: 0 = 76 MHz, 1 = 87 MHz
• Power down: Write either 0 (powerdown) or 1 (powerup) to register 0x02. Set register bits 9 and 10 of register 0x04.
• Set soft-mute: On un-mute, clear bit 9 of register 0x04. On mute, set bits 9 and 10 of register 0x04.
• Set de-emphasis: Set or clear bit 11 of register 0x04, just like the si4700.
• Set channel spacing: Write the 2-bit channel space code in SPACE, similar to si4700, but in a different location.
• Set frequency: Calculate the channel code CHAN = (Fdesired - Flow) / 50 KHz, where Fdesired is the frequency to tune to and Flow is the lowest frequency in this band. Then write CHAN together with the TUNE bit set. Wait 70 ms, read 4 bytes status. Verify that READCHAN = CHAN and that STC is set, if so we're done, otherwise clear TUNE and try the whole procedure again up to 25 times.
• Read RSSI: Read 4 bytes from the radio chip. If AFCRL is set, assume 0, otherwise return RSSI bits.

Read 128 bytes from the chip, check if bytes[4] == 0x58. If this is the case, the chip has been detected. Now write 2 bytes (0x200) and wait a bit (10 ms), then check bytes[6] and compare against 0. If 0, write a set of 72 initialisation values, else write a set of 82 initialisation values.

Mute radio

Set or clear the DMUTE bit, just like the si4700. Also set bits 9 and 10 of register 0x04 and the four lowest bits of register 5 (VOLUME).

Force mono

Set or clear the MONO bit, just like the si4700.

Set band

Write the 2-bit band code in BAND, similar to the si4700, but in a different location.

The lowest bit of BAND indicates the start of the band as follows: 0 = 76 MHz, 1 = 87 MHz

Power down

Write either 0 (powerdown) or 1 (powerup) to register 0x02. Set register bits 9 and 10 of register 0x04.

Set soft-mute

On un-mute, clear bit 9 of register 0x04. On mute, set bits 9 and 10 of register 0x04.

Set de-emphasis

Set or clear bit 11 of register 0x04, just like the si4700.

Set channel spacing

Write the 2-bit channel space code in SPACE, similar to si4700, but in a different location.

Set frequency

Calculate the channel code CHAN = (Fdesired - Flow) / 50 KHz, where Fdesired is the frequency to tune to and Flow is the lowest frequency in this band. Then write CHAN together with the TUNE bit set. Wait 70 ms, read 4 bytes status. Verify that READCHAN = CHAN and that STC is set, if so we're done, otherwise clear TUNE and try the whole procedure again up to 25 times.

Read RSSI

Read 4 bytes from the radio chip. If AFCRL is set, assume 0, otherwise return RSSI bits.