Si24R1 is a 2.4G RF chip with proprietary intellectual property rights specially designed by Wuxi Zhongke Micro for low-power wireless communication applications. At present, it is mainly aimed at low-power school communication, 2.4G parking lot, smart home, wireless audio and other fields.
Of course, this chip has entered the public's field of vision because it is compatible with the NRF24L01P chip of friends. As a result, it was marked with the domestic NRF24L01P label. What's more, the original SI24R1 LOGO of the chip was polished off and marked as NRF24L01P, which caused a lot of unnecessary losses to many customers. Everyone's directional understanding is that domestically produced things are always different from those imported from abroad, and so on. In fact, when many customers use Si24R1, through certain control and design, the unique characteristics of Si24R1 can be brought into play.
Different chip designs require different RF wiring and MCU control, so I would like to share some of the problems and solutions I know:
1. After entering the low-power (shutdown) mode, the power consumption may still be 1mA Around, normally it should be around 1.5uA.
Solution: Since the chip adopts CMOS technology, when the chip is in shutdown mode, the digital input pins of the chip, CE, CSN, SCK, MOSI, must be low level, that is, in shutdown mode, and the above four input pins The output of the MCU connected to the pin must be a low level, not a high-impedance state or a high level. Otherwise, due to the accumulation of charge at the input, the internal circuit cannot be turned off, resulting in an increase in power consumption.
2. When using Si24R1's so-called 7dbm transmit power, the distance does not seem to increase much, and wireless audio customers feel that there will be a lot of noise.
Solution:
1. The nRF24L01+ of a friend does not require the metal pad at the bottom of the chip to be grounded, and the Si24R1 specification does not require grounding. This is because the transmit power is only 0dbm. When the chip transmit power is greater than 0dbm, the metal pad at the bottom of the chip is welded The disk will have a lot of white noise coupled to the ground, and the reference design of nRF24L01+ has a 3.3V power line under the metal PAD. If the Si24R1 7dbm transmit power is used and the 3.3V line at the bottom is not removed, those noises will interfere. to the power supply, thereby increasing the packet loss rate and communication distance of communication. Some netizens suggested on the Internet that using Si24R1 to replace the NRF24L01P power supply needs to add a large capacitor for filtering. This approach is feasible in a certain design, but there are still some friends who have not solved the problem. Therefore, in order to achieve better performance, especially when transmitting high power, it is recommended that all PADs at the bottom of the chip be grounded and the 3.3V traces should be re-routed.
2. Wireless audio customers cannot solve the problem of noise after the first point. It is necessary to consider the source of the noise and the purity of the power supply, because the SI24R1 is more sensitive to the power supply than the SI24R1, and the user can improve it through the wiring sequence. Originally, the wiring sequence of the power supply is LDO-MCU-ADC-RF. The whole process is designed, and the wiring is convenient and in line with the process. However, the disadvantage of this design is that the noise of the entire MCU and ADC conversion (actual noise maker) is all crosstalk to RF. power supply, thereby affecting wireless communication. Therefore, the user can change the design of the power supply wiring. After the LDO comes out, it will be divided into two channels, one to the RF, one to the MCU+ADC.
3. The user has been using nRF24L01P, and found that the power consumption suddenly increased a lot after replacing it with Si24R1.
Of course, this chip has entered the public's field of vision because it is compatible with the NRF24L01P chip of friends. As a result, it was marked with the domestic NRF24L01P label. What's more, the original SI24R1 LOGO of the chip was polished off and marked as NRF24L01P, which caused a lot of unnecessary losses to many customers. Everyone's directional understanding is that domestically produced things are always different from those imported from abroad, and so on. In fact, when many customers use Si24R1, through certain control and design, the unique characteristics of Si24R1 can be brought into play.
Different chip designs require different RF wiring and MCU control, so I would like to share some of the problems and solutions I know:
1. After entering the low-power (shutdown) mode, the power consumption may still be 1mA Around, normally it should be around 1.5uA.
Solution: Since the chip adopts CMOS technology, when the chip is in shutdown mode, the digital input pins of the chip, CE, CSN, SCK, MOSI, must be low level, that is, in shutdown mode, and the above four input pins The output of the MCU connected to the pin must be a low level, not a high-impedance state or a high level. Otherwise, due to the accumulation of charge at the input, the internal circuit cannot be turned off, resulting in an increase in power consumption.
2. When using Si24R1's so-called 7dbm transmit power, the distance does not seem to increase much, and wireless audio customers feel that there will be a lot of noise.
Solution:
1. The nRF24L01+ of a friend does not require the metal pad at the bottom of the chip to be grounded, and the Si24R1 specification does not require grounding. This is because the transmit power is only 0dbm. When the chip transmit power is greater than 0dbm, the metal pad at the bottom of the chip is welded The disk will have a lot of white noise coupled to the ground, and the reference design of nRF24L01+ has a 3.3V power line under the metal PAD. If the Si24R1 7dbm transmit power is used and the 3.3V line at the bottom is not removed, those noises will interfere. to the power supply, thereby increasing the packet loss rate and communication distance of communication. Some netizens suggested on the Internet that using Si24R1 to replace the NRF24L01P power supply needs to add a large capacitor for filtering. This approach is feasible in a certain design, but there are still some friends who have not solved the problem. Therefore, in order to achieve better performance, especially when transmitting high power, it is recommended that all PADs at the bottom of the chip be grounded and the 3.3V traces should be re-routed.
2. Wireless audio customers cannot solve the problem of noise after the first point. It is necessary to consider the source of the noise and the purity of the power supply, because the SI24R1 is more sensitive to the power supply than the SI24R1, and the user can improve it through the wiring sequence. Originally, the wiring sequence of the power supply is LDO-MCU-ADC-RF. The whole process is designed, and the wiring is convenient and in line with the process. However, the disadvantage of this design is that the noise of the entire MCU and ADC conversion (actual noise maker) is all crosstalk to RF. power supply, thereby affecting wireless communication. Therefore, the user can change the design of the power supply wiring. After the LDO comes out, it will be divided into two channels, one to the RF, one to the MCU+ADC.
3. The user has been using nRF24L01P, and found that the power consumption suddenly increased a lot after replacing it with Si24R1.
Solution: For users who have used nRF24L01+, usually users will configure the transmit power at 0dbm, and the register configuration at this time is 4dbm for Si24R1, and the current consumption is 16mA, which is more consumption than 0dbm configuration. The current should be larger than 4-5mA. When the system is powered by a button battery, you need to pay attention to this problem. If you don't need high transmit power, please adjust the transmit power configuration to low power mode. For specific configuration, refer to the chip manual (can be configured as 100 mode, 1dbm transmit power mode). The maximum power of Si24R1 is 7dbm, which requires special configuration registers, please refer to the manual.
Ownership of Shenzhen Kinetic Century Technology Co., Ltd.
Technical Engineering: Zhao Zhihong.