Crystal substitute using si5351 – part 1 described the first part of a series on an inexpensive crystal replacement using a si5351-A / MS5351M PLL chip and an ATTiny controller.
Above is an example pair of inexpensive modules, less than $10 for the pair (incl shipping). Both boards are powered from 5V, the left hand module is a ATTiny85 dev board, it has a small 3.3V regulator on board. The dev board uses a DIP chip, so it can easily be programmed in a device programmer and then inserted in the socket.
Above is a cold start of the module, error settles around +137ppm.
Above is an Allan Deviation chart for this module referenced to a Trimble Thunderbolt (module freq=10M-137.5ppm). Short term stability is not too bad, the bigger problem is likely temperature response over hours and days. The crystal on this cheap module has 140ppm error, so specification accuracy would be worse than that, and temperature stability is probably about the same for 10-60°. So, that is quite likely around 3ppm/°.
Note that the Adafruit module that this appears to be cloned from is specified with a crystal of 30ppm accuracy and similar temperature stability over 10-60° (0.6ppm/°).
Development programming
Above is a screenshot of the EEPROM configuration data with two selectable configuration sets (burstsets) programmed. The ATTinyx5 has two pins for selection of one of four burstsets, the ATTinyx4 chips have four pins available for selection one of up to 16 burstsets, limited in both cases by the EEPROM available.
Bus Pirate v5
A Python script was written to parse the exported configuration from Clockbuilder Pro and create the Bus Pirate commands to be pasted into a terminal emulator (Teraterm v5). Bus Pirate 5 is not backwards compatible with v4 and v3, so the script accepts an argument to set the language version. The script also writes a binary file of the EEPROM image for use with a device programmer.
Teraterm was used as it allow specification of a pause at the end of each line to allow Bus Pirate to execute the command.
#!/usr/bin/env python
# coding: utf-8
from pathlib import Path
import csv
import os
import sys
import struct
print('\n'+Path(__file__).stem+' v1.03 20240330 Owen Duffy\n')
import getopt,sys
def usage():
print(Path(__file__).stem+" [-a hexaddress] [-m mversion][-o outprefix][-b bfilename][-p pfilename][-t toclen] ifile1 [ifilen]...")
sys.exit(2)
try:
opts,args=getopt.getopt(sys.argv[1:],"ha:b:m:o:p:t:v:",["help","address=","bfilenane=","mversion=","outprefix=","pfilename=","toclen=","verbose="])
except getopt.GetoptError as err:
# print help information and exit:
print(err) # will print something like "option -a not recognized"
usage()
sys.exit(2)
verbose=False
ifilesn=0
ifilenames=[]
if len(args)<1:
usage()
for arg in args:
ifilenames.append(arg)
print(arg,ifilesn)
ifilesn=ifilesn+1
chip=0xc0
toclen=ifilesn+3
bpv=5
p=Path(ifilenames[0])
pfilename=p.with_suffix('.pllldri')
bfilename=p.with_suffix('.bp')
for o, a in opts:
if o == "-v":
verbose = True
elif o in ("-h", "--help"):
usage()
sys.exit()
elif o in ("-a", "--address"):
chip=int(a,16)
elif o in ("-m", "--mversion"):
bpv=int(a)
elif o in ("-b", "--bfilename"):
bfilename=a
elif o in ("-o", "--outprefix"):
prefix=Path(a)
pfilename=prefix.with_suffix('.pllldri')
bfilename=prefix.with_suffix('.bp')
elif o in ("-p", "--pfilename"):
pfilename=a
elif o in ("-t", "--toclen"):
toclen=a
if toclen0):
if row[0].startswith("#"):
continue
addr=int(row[0])
data=int(row[1].rstrip('h'),16)
if(addr-1==lastaddr):
bfile.write(' 0x{:02x}'.format(data))
burst=burst+struct.pack('B',data)
burstlen=burstlen+1
else:
bfile.write('\n[ 0x{:02x} 0x{:02x} 0x{:02x}'.format(chip,addr,data))
if(burstlen>0):
burst=struct.pack('B',burstlen)+burst #prepend burstlen
pbuf[i]=pbuf[i]+burst #write to file buffer
burstsetlen=burstsetlen+burstlen+1
burstn=burstn+1
burst=struct.pack('BB',addr,data)
burstlen=2
#burstn=burstn+1
lastaddr=addr
# print(row)
# print('burstlen2: ',burstlen,burstn)
if(burstlen>0):
burst=struct.pack('B',burstlen)+burst #prepend burstlen
pbuf[i]=pbuf[i]+burst #write to file buffer
burstsetlen=burstsetlen+burstlen+1
burstn=burstn+1
pbuf[i]=struct.pack('BB',burstn,burstsetlen)+pbuf[i] #prepend burst list hdr
# print('burstlen2: ',burstlen,burstn)
bfile.write(' ]\np\nw\ni\n\n')
i=i+1
#write pfile header
buf=b'\x01\x03\x00'+struct.pack('B',chip)+struct.pack('B',len(pbuf))
#append toc
offs=5+toclen*2
i=0
for x in pbuf:
buf=buf+struct.pack('<H',offs) #append toc entry
offs=offs+len(x)
i=i+1
for j in range(i,toclen):
buf=buf+b'\xff\xff' #append empty toc records
#append burst sets
for x in pbuf:
buf=buf+x
pfile.write(buf)
pfile.close
bfile.close()
Above is the Python script.
HiZ> m
Mode selection
1. HiZ
2. 1-WIRE
3. UART
4. HDUART
5. I2C
6. SPI
7. 2WIRE
8. DIO
9. LED
10. INFRARED
x. Exit
Mode > 5
Use previous settings?
I2C speed: 100 kHz
Clock stretching: OFF
y/n, x to exit (Y) > n
I2C speed
1kHz to 1000kHz
x. Exit
kHz (400kHz*) > 100
Clock stretching
1. OFF*
2. ON
x. Exit
OFF (1) > 1
Mode: I2C
I2C> W
Power supply
Volts (0.80V-5.00V)
x to exit (3.30) > 3.3
Maximum current (0mA-500mA), for none
x to exit (none) > 100
3.30V requested, closest value: 3.30V
100.0mA requested, closest value: 100.0mA
Power supply:Enabled
Vreg output: 3.3V, Vref/Vout pin: 3.3V, Current: 28.4mA
I2C> P
Pull-up resistors: Enabled (10K ohms @ 3.3V)
I2C> i
This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) this device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.
Bus Pirate 6
https://BusPirate.com/
Firmware main branch @ 8e51eb6 (2024-10-31T11:09:12Z)
RP2350B with 512KB RAM, 128Mbit FLASH
S/N: 2EAE869F8943242C
Storage: 0.10GB (FAT16 File System)
Configuration file: Loaded
Available modes: HiZ 1-WIRE UART HDUART I2C SPI 2WIRE DIO LED INFRARED
Active mode: I2C
I2C speed: 100 kHz
Clock stretching: OFF
Display format: Auto
Data format: 8 bits, MSB bitorder
Pull-up resistors: ON
Power supply: ON (3.3V/3.29V)
Current limit: OK (36.9mA/100.0mA)
Frequency generators: OFF
1.Vout 2.IO0 3.IO1 4.IO2 5.IO3 6.IO4 7.IO5 8.IO6 9.IO7 10.GND
36.9mA SDA SCL - - - - - - GND
3.3V 3.3V 3.2V 3.2V 3.3V 3.3V 3.2V 3.2V 3.2V GND
I2C> [ 0xc0 0x02 0x53 0x00 0x20
I2C START
TX: 0xC0 ACK 0x02 ACK 0x53 ACK 0x00 ACK 0x20 ACK
I2C> [ 0xc0 0x07 0x00
I2C REPEATED START
TX: 0xC0 ACK 0x07 ACK 0x00 ACK
I2C> [ 0xc0 0x0f 0x00 0x0c 0x8c 0x8c 0x8c 0x8c 0x8c 0x8c 0x8c
I2C REPEATED START
TX: 0xC0 ACK 0x0F ACK 0x00 ACK 0x0C ACK 0x8C ACK 0x8C ACK 0x8C ACK 0x8C ACK
0x8C ACK 0x8C ACK 0x8C ACK
I2C> [ 0xc0 0x1a 0xb5 0xa7 0x00 0x0f 0xf3 0x00 0x24 0xfb
I2C REPEATED START
TX: 0xC0 ACK 0x1A ACK 0xB5 ACK 0xA7 ACK 0x00 ACK 0x0F ACK 0xF3 ACK 0x00 ACK
0x24 ACK 0xFB ACK
I2C> [ 0xc0 0x2a 0x00 0x04 0x00 0x2a 0xe0 0x00 0x00 0x00
I2C REPEATED START
TX: 0xC0 ACK 0x2A ACK 0x00 ACK 0x04 ACK 0x00 ACK 0x2A ACK 0xE0 ACK 0x00 ACK
0x00 ACK 0x00 ACK
I2C> [ 0xc0 0x5a 0x00 0x00
I2C REPEATED START
TX: 0xC0 ACK 0x5A ACK 0x00 ACK 0x00 ACK
I2C> [ 0xc0 0x95 0x00 0x00 0x00 0x00 0x00 0x00 0x00
I2C REPEATED START
TX: 0xC0 ACK 0x95 ACK 0x00 ACK 0x00 ACK 0x00 ACK 0x00 ACK 0x00 ACK 0x00 ACK
0x00 ACK
I2C> [ 0xc0 0xa2 0x00 0x00 0x00 0x00
I2C REPEATED START
TX: 0xC0 ACK 0xA2 ACK 0x00 ACK 0x00 ACK 0x00 ACK 0x00 ACK
I2C> [ 0xc0 0xb7 0x92 ]
I2C REPEATED START
TX: 0xC0 ACK 0xB7 ACK 0x92 ACK
I2C STOP
I2C> p
Pull-up resistors: Disabled
I2C> w
Power supply: Disabled
I2C> i
This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) this device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.
Bus Pirate 6
https://BusPirate.com/
Firmware main branch @ 8e51eb6 (2024-10-31T11:09:12Z)
RP2350B with 512KB RAM, 128Mbit FLASH
S/N: 2EAE869F8943242C
Storage: 0.10GB (FAT16 File System)
Configuration file: Loaded
Available modes: HiZ 1-WIRE UART HDUART I2C SPI 2WIRE DIO LED INFRARED
Active mode: I2C
I2C speed: 100 kHz
Clock stretching: OFF
Display format: Auto
Data format: 8 bits, MSB bitorder
Pull-up resistors: OFF
Power supply: OFF
Frequency generators: OFF
1.Vout 2.IO0 3.IO1 4.IO2 5.IO3 6.IO4 7.IO5 8.IO6 9.IO7 10.GND
OFF SDA SCL - - - - - - GND
0.1V 0.1V 0.1V 0.0V 0.0V 0.0V 0.0V 0.0V 0.0V GND
I2C>
Above is a console log of Bus Pirate v6 programming of the PLL for development testing.
… more to follow.