我正在尝试使用 Raspberry Pi 3b+ 通过 SPI 从 AEAT9922 角度传感器(HEDS-9922EV 评估板)获取数据。稍后我们将转移到 jetson nano 或 xavier nx。 使用给出的代码,我们得到了我无法解释的垃圾数据。我最好的猜测是我们误解了数据表或对 SPI 通信的普遍误解。
编辑:对于 Angular 数据,它总是返回:00000000 10000000 00000000 00000000
数据表链接:这里
设置:
def __init__(self, bus, device):
self.spi = spidev.SpiDev()
self.spi.open(bus, device)
self.spi.max_speed_hz = 5_000_000
self.spi.mode = 1
角度方法:
def read_angle(self):
# SPI4 read command for position data (address 0x3F)
address = 0x3F
read_flag = 0x4000 # Bit 14
read_cmd = address | read_flag
read_cmd |= self.compute_parity(read_cmd) << 15
# Split the 16-bit command into two 8-bit chunks
cmd_msb = (read_cmd >> 8) & 0xFF # Most significant byte
cmd_lsb = read_cmd & 0xFF # Least significant byte
# Send the command and receive the response
resp = self.spi.xfer2([cmd_msb, cmd_lsb, 0, 0]) # sending 4 bytes in total for receiving 18 bits
# Combine the two bytes into a single 32-bit value
angle = (resp[0] << 24) + (resp[1] << 16) + (resp[2] << 8) + resp[3] # assuming big-endian byte order
# Extract the parity bit
parity = (angle >> 31) & 0x01
# Extract the error flag
ef = (angle >> 30) & 0x01
if ef:
print("Warning: Error flag set in angle reading.")
# Extract the position data
data = (angle >> 12) & 0x3FFFF # assuming 18-bit position
# Check the parity bit
if parity != self.compute_parity(data):
raise Exception("Parity error in SPI response")
return data
最后是数据表中的两个屏幕截图,其中包含(希望)最重要的信息。
[位置读取:(https://i.stack.imgur.com/xnN6y.png)]
[命令和数据帧:(https://i.stack.imgur.com/3Y55z.png)]
我们尝试了什么: